Effects of Atrazine Exposure on Anuran Amphibians in North America


Atrazine is a commonly used herbicide for the elimination of weeds that are found in agriculture plots. It is cheaply available for farmers and helps them with keeping low production costs. The chemical is found as agricultural runoff and when it is exposed to organisms it acts as an endocrine disrupting chemical, which caused an increase in estrogen and decrease in testosterone levels. In North America there has been a rapid decline of anuran amphibian species. Various scientists have linked the decline of anuran amphibians to the exposure of atrazine. The relationship between atrazine and amphibian decline is defined through abnormalities in the gonad development of tadpoles and feminized sex ratios of the amphibian population at lower concentrations than what is legally allowed in the water. Such adverse effects highlight the linked between the long-term exposure of atrazine to the population decline of anuran amphibians. This literature review will focus on how atrazine affects the reproductive system of frogs. There will be a focus on the effects of atrazine with regards to, gonads, sex ratios, and its connection to the population decline.

Keywords: Anuran Amphibians, Atrazine, Sex Ratios, Population Decline.


Many amphibian species are at risk of extinction around the world. Nearly, 32% of the world’s amphibians are threatened with extinction (Climate Change Canada 2010). In regards to Canada of the 47 species found in the country 20% are at risk of extinction. The dwindling population of amphibians across the world has sparked an increase discussion relating to factors that may have contributed to this threat. Over the past twenty years there has been an increase in concern on what factors have possibly contributed to the population decline of amphibians. Major threats include habitat loss, invasive species, pollution, and climate change. Some areas of southern Canada have had a 90% in wetland loss with the remaining 10% containing pollutants from agricultural or urban runoff (Climate Change Canada 2010).

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  As agricultural practices become modernized chemicals such as herbicides have been applied in greater quantities. Farmers have benefited from the selective, effective and inexpensive herbicide called Atrazine. This chemical has helped farmers manage weeds and reduce production costs (Ackerman 2007). When applied to a plant, atrazine affected the plastoquinone-binding protein in photosystem II and caused oxidative damage caused the death of the plant (Appleby,Franz and Carpy 2001). Consequently, Atrazine has received attention as the main potential cause of amphibian declines particularly in frogs. Field studies have shown a correlation regarding population declines in amphibians and agricultural runoffs (Houlahan and Findlay, 2003). The chemical also acted as an endocrine disrupting chemical (EDC) at low doses when it is exposed to organisms. Atrazine interfered with the catalytic activity of aromatase. Aromatase is an enzyme that converted androgens to estrogen. An effect the disruption showed was an increased level of estrogen in an organism. Furthermore, an increase of malformed gonads in frogs living in agricultural areas where pesticides and fertilizers had been applied extensively was observed (Ouellet et al., 1997; Hayes 2010). Some studies have also observed a sex reversal in which the populations underwent increased feminization and lower instances sexual competitiveness of frogs (Hoskins and Boone 2017; Langlois et al. 2010).
 The topic of atrazine affecting the reproductive system of frogs is a western dilemma. Geographically, many of these studies were conducted in North America with no studies used in this review from the developing world. The studies are a mixture of field and lab work. This is a local issue as atrazine is heavily used in Canada and tends to be found in drinking water at low levels consisting of 5 µg/L (Health Canada 1993). There would be differences in how the studies would be treated around the world since factors such as climate, regulations, husbandry and species of frogs used vary.
 In this review I will focus on how atrazine affects the reproductive system of frogs. There will be a focus on the effects of atrazine with regards to gonads, sex ratios, and its connection to the population decline.

Amphibian Population Decline

Numerous species of Anuran amphibians (i.e frogs and toads) have experienced a population decline across a variety habitats worldwide. In the 1990s there was a high mortality rate in various amphibian populations and it caused a rapid of a population declines in wetlands ever since (Wake, 1991). An ecological decline is defined as the net loss of a population that is higher than the birth rate of the normal population (Stuart et al., 2004). Toads and frogs formed approximately 90% of all amphibian’s species and were deemed as an important connection to the health of an ecosystem (Hayes, et al., 2002). The global amphibian decline has caused a lot of concern for both researches , as amphibians are often reference point for any positive or detrimental environmental change (Wake and Vredenburg, 2008). Amphibian’s permeable skin, that is used for gas exchange and osmo-regulation, makes them sensitive to contaminants and pathogens that cause adverse effects on their overall health. Any disturbances such as habitat degradation, pollution, the increased introduction of destructive invasive species, and climate change can decrease their population size (Climate Change Canada, 2010). Particularly, popular herbicides such as atrazine received attention as frogs are exposed to the harmful effects of the environmental contaminant throughout different life-stages (Hayes, et al., 2002).

Effects of the Gonadal development of Anuran amphibians when Exposed to Atrazine

  EDCs such as atrazine have been researched heavily in frogs for numerous reasons. The time of the year when atrazine is applied is not ideal for anuran amphibians as it is mostly applied in the spring in the same time as its breeding season (Conant, 1998). The highest amount of atrazine in the water was found at the same time as the larval development of anuran amphibians (Conant, 1998). The larvae period is also the time when gonadal differentiation occurred and is regulated by hormones such as estrogen and testosterone (Hayes et al. 2002) and as the interference with the natural sexual development of the organisms caused long term gonad abnormalities that deterred their breeding capabilities.

  Various studies have examined the gonadal development of frogs when the organisms were exposed to atrazine. In the University of Berkeley, Hayes et al., 2002 had observed the full gonad development of 150 African Clawed frogs (Xenopus laevis) period over a period of 46 days. 75 frog eggs were obtained within the lab at Berkeley and 75 wild eggs were obtained from an uncontaminated pond located in Wisconsin. Each organism was exposed to different concentrations of atrazine (0,0.1,0.4,0.8,1, and 25 parts per billion).After the 46 days each frog was euthanized. A gonadal analysis of each specimen’s ovaries or testes were conducted post mortem and marked with Mallory’s trichrome stain (Hayes et al., 2002). The control group did not have any gonadal malformities (pFor instance, 20% of the total population had developed multiple gonads where certain frogs had developed six gonads or had developed as a hermaphrodite that contained multiple testes and ovaries at concentrations as low as 0.1 parts per billion. Frogs were classified as Hermaphrodite if they had developed testicular oocytes (figure 1)(pX.laevis were more affected by the exposure to atrazine than their female counterparts. Males suffered from a 30 % underdevelopment of testicular tissue, laryngeal size and some samples were classified as hermaphrodites but were found as genetic males (p A study by Mccoy et al. (2008) also observed gonadal malformities of 100 wild Bufo marinus from five different wetland sites that contained herbicides such as atrazine and round up in the South Florida area over a period of two years. Each organism was euthanized when the gonadal analysis commenced. Mccoy et al. (2008) survey results found an increasing number of organisms that had become intersex. The intersex B.marius had more estrogen than testosterone and a higher of number of ovaries than testes. The male specimen were also smaller than the control, developed oocytes, underdeveloped testes, low testosterone levels and a decreased production of sperm (pMccoy et al. ,2008). Both studies theorized that the frog populations were demasculinized from chronic exposure of atrazine as the results had affected more male samples than female through underdeveloped testes, smaller laryngeal size and low testosterone levels.

Figure 1: A sample of Gonadal abnormalities found in an atrazine treated Xenopus laevis hermaphrodite. This sample wsa exposed to 1 parts per billion of atrazine. As a result, the sample produced multiple testes (labelled T) and ovaries (labelled O). The right side of the picture was a cross section of the gonads. The pairs of testes were deemed smaller than the male control group testes and lack of pigmentation in the ovaries (E). The results above was common in many hermaphrodite gonad samples in exposures between 1 -25 parts per billion (p

Figure 2: Testosterone concentrations across many different groups of Bufo Marinus. The male control group had the highest amount of testosterone. The male experimental group significantly had a lower amount of testosterone. The agricultural exposed males had about the same amount of testosterone levels as the control females. The error bars are from a 95 % confidence interval and significance p value of 0.001 in all the bars except the control which the p value is 0.05.Credit to Mccoy et al 2008.

A lack of consensus existed on the point of gonadal malformities from the exposure to atrazine. Coady et al. (2004) disagreed that gonadal malformations stemmed from atrazine exposure. 2500 Rana clamitan eggs were collected from an uncontaminated rural pond in Michigan and placed the eggs in filtered water tanks until the samples hatched in which was completed in 8 days (Coady et al., 2004). After the sample organisms hatched samples were placed in 10 and 25 µg/L of atrazine in which a total of nine replicated of each sample was created. The solution was applied into the water every 72 hours for a period of 273 days. When all the samples of R.clamitan reached metamorphosis the specimens were transferred to filtered water tanks and left in the tanks for another 234 days when the sample were terminated. The gonads of each sample were analyzed in post mortem (Coady et al. ,2004). Only 5.9% of the population suffered from gonad abnormalities and none of the sample gonads were hermphodites (p From the three studies Coady et al. (2004), presented various limitations since the experimental study presented many inconsistences. Firstly, the study’s mortality rate from all specimens was approximately 73.3-83 % which was significantly higher the other studies mortality rate of 10% (Mccoy et al.,2004; Hayes et al.,2002; Mccoy et al., 2008). Usually when there is a mortality rate of above 15 % the study is deemed as insignificant since the specimens were bad conditions throughout the experiments. Therefore, it is not possible to truly evaluate the effects of atrazine on the development of frog gonads. The samples in the Coady et al. study were also not placed in the chemically induced water for the whole study like the other two studies observed in their experiments and that could have also effected the results of the experiment. There was also a conflict of interest in the study. Syngenta the company that funded the study is a major producer of atrazine. The company is known to hire scientists to argue against any results that may present atrazine negatively (Rohr and Mccoy,2010). Although the company should defend its product if the results are unwarranted and are found to have serious flaws , the direction the company tries to discredit independent researchers is bad. By downplaying the credibility of researchers, it misleads the public to think that atrazine does not affect anuran amphibians and the environment. (Rohr and Mccoy,2010). It can then be concluded that gonad malformations negatively affected the frog populations as it acted as an environmental stressor and demasculinized the populations sampled.Effects of Sex Ratios in Atrazine Exposed Frogs


There is strong convergent evidence that the sex ratios of frogs were feminized due to the exposure of atrazine. Genetic males have ZW sex chromosomes while genetic female anuran amphibians have ZZ sex chromosomes. In Cornwall, Ontario , Canada a study by Langlois et al. 2010 reported the sex ratios of a population of 750 wild Rana pipiens tadpoles . The samples were found within five atrazine contaminated sites of the Raisin river (Ontario). The rivers contained 1.6 μg/L of atrazine and when transferred to the lab each group was exposed to 0, 0.1 and 1.8 μg/L of atrazine over a period of 78 days when the R.pipiens reached the climax of metamorphosis. Before the sex ratio count was conducted all the samples were terminated with a 1% solution of MS-222 and dry ice. The sex ratio test conducted through a dissection of the whole populations gonads. Furthermore, each gonad was classified as male (ZW) or female (ZZ) through a microscope (4x) (Langlois et al., 2010). The study stated a 1:0.6 and of male to female R.pipens in the control group and was within the normal sex ratio range for the species (1:0.5). Tadpoles exposed to 1.8 μg/L of atrazine skewed the sex ratio to 1:1.4 male to female. Low exposures to atrazine stayed with the ideal sex ratio range (1:0.8) (pR.pipens for breeding. Certain genetic male(ZW) R.pipens exposed to 1.8 µg/l of atrazine had the appearance of a female were deemed as sex reversed subjects and were included in the female group of sex ratios. A recent study by Boone and Hoskins 2017 also determined a connection between feminized sex ratios and the exposure to atrazine. 280 Blanchard’s cricket frogs (Acris blanchardi) were exposed to various concentrations of atrazine ( 0, 0.1, 1, and 10 μg /L) over a period of two months. The experiment was terminated with a 1% solution of MS 222. The determination of sex ratios was also conducted by a visual inspection for male testes or female ovaries from the gonads of A. blanchardi (Boone and Hoskins, 2017). Atrazine feminized the sex ratios of A.blanchardi at a concentration of 0.1 μg /L and the study theorized the skewed ratio resulted from a atrazine mediated a male(ZW) to female sex reversal (ZZ) (figure 3). Furthermore the study connected atrazine as an estrogen mimicker in which had the ability through sex reversal to lower the fertility rate of males and produced a scarcity of males available to breed with female A.blanchardi (Hoskins and Boone, 2017). Both experimental studies determined atrazine created Female-biased sex ratios and a consequence of the skewed results was the possibility of a declined amphibian population.

Figure 3: A logistical regression of the effects atrazine had on the sex ratios of Acris blanchardi. The dotted lined presented a 1:1 ratio of male to female population. Concentrations of 0.1 and 10 μg /L represent a feminized sex ratio of approximately 1:0.4 and 1:0.35 respectively. Both results were deemed different then the control as it was lower than the ideal sex ratio range of 1:1. The statistical significance is at p
Connection of Atrazine to the Population Decline of Anuran Amphibians

 Anuran amphibian species are heavily reliant on the their habitat for the for reproduction and larval development; Therefore, the organism were vulnerable to pollutants such as atrazine. As an estrogen induced endocrine disrupting chemical (EDC) the effects of atrazine is deemed more of a concern for male frogs as it created gonadal malformations such as testicular oogenesis and sex reversal (Hayes et al.,2002). When an atrazine exposed male had a decline in testosterone morphologies such as the demasculinized larynx, low sperm count and smaller body muscle mass it is unable to attract a female for breeding as it mimics characteristics of female (Hayes et al. 2002). If it does attract a mate the low sperm count lowered the chance of breeding success. Sex reversal also feminizes the sex ratios in which there would be a lower amount of truly genetic males than females. As a result, over time the population would decline as there are not enough males to mate with females. A recent study from 2010 from North Carolina linked the low body mass of atrazine exposed Rana pipens overall impeded their overall development and survival (Koprivnikar,2010). Koprivnikar placed 384 tadpoles in different concentrations of atrazine (0,3,300 μg /L). 450 tadpoles were placed in dechlorinated tap water and after 216 hours each the tadpoles were exposed to 20 cercariae of a trematodes (Echinostoma trivolvis). The control group of each study were only exposed to dechlorinated tap water. A group of 32 tadpoles were exposed to both atrazine (3 μg /L) and trematodes (Koprivnikar,2010). The study was terminated after 46 days when the tadpoles were in mid metamorphosis. Tadpoles exposed to atrazine at 300 μg /L were annexed in the results as the mortality rate was at 100 percent. For tadpoles exposed to only 3 μg /L of atrazine had a mortality rate of 25 percent. Parasite ridden tadpoles only experienced a mortality rate of 20 percent. The mortality rate was at 35 percent when the tadpoles were exposed to both atrazine and trematodes. Koprivnikar theorized that the higher rate of mortality for tadpoles exposed to both atrazine and trematodes was due to low body mass and a slower developmental rate. When the body mass was lower many the tadpoles had become stressed, could not produce a sufficient immune response as the immune system of the organisms were underdeveloped. Consequently, the tadpoles low body mass was linked to the atrazine exposure (Koprivnikar,2010). When amphibians were exposed to various stressors the metamorphic process of frogs are hindered. Impediment to development is detrimental to the amphibian population as lower number of creatures would have reached full sexual development. Over time the population would decline due to feminization and a high susceptibility to pathogens.


 Through the review of several studies it can be concluded that the exposure to atrazine can affect the gonadal development and sex ratios of anuran amphibians in North America. Numerous studies determined the feminization of the population as male frogs had underdeveloped reproductive parts, fertility problems and a smaller body mass. Some population of genetic males had become hermaphrodites as the studies observed the development of testicular oocytes (Mccoy et al.,2008; Hayes 2010). Another study determined that the exposure to atrazine did not produce gonadal malformations to exposed amphibians (Coady et al.,2004). The results of the study could not be deemed as valid due to the high mortality rate of the control group. Feminization of sex ratios were due to the sex reversal of male to female frogs. Many of genetic males were deemed as female as the organism had female characteristics. The skewed sex ratio produced a scarcity of male frogs to breed with females (Hoskins and Boone,2017). The population decline of anuran amphibian was linked to the gondal development and feminized sex ratios.

Despite, the consensus of the various experimental studies whom suggest that atrazine produced adverse effects on Anuran amphibians, the results should not be assumed in all amphibian species and other organisms. Firstly, the development of the amphibians in the studies were mainly produced in the lab and the results may differ in long term field studies. The differences may come as contaminated wetlands may have a combination of herbicides and other contaminants in the water that could also affect the metamorphic development of anuran amphibians. Many organisms have different dose-response rates may not be affected by the atrazine levels as shown in the review. Further research is needed to determine if atrazine or a mixture of herbicides had a long-term effect on several amphibian species in the field rather than just the lab. Exposure of atrazine should also be researched with other species such as fish and mammals. If more studies proved that the herbicides produced an adverse effect on amphibians that produced a decline in the population, there would be a need for governmental policy reform. Examples for policy reforms could be lowering the amount of pesticides allowed in the water and to place incentives (e.g. tax breaks, subsidies) for farmers move towards alternative management methods such as biological control.

Literature Cited

Ackerman,F. (2007). The Economics of Atrazine. International Journal of Occupational and Environmental Health 13:4, 444. https://doi.org/10.1179/oeh.2007.13.4.437

Conant, R. A. (1998). Field Guide to Reptiles and Amphibians: Eastern and Central North America. Boston: Houghton-Mifflin.

Coady, K., Murphy, M., Villeneuve, D., Hecker, M., Jones, P., Carr, J., . . . Giesy, J. (2004). Effects of Atrazine on Metamorphosis, Growth, and Gonadal Development in the Green Frog (Rana Clamitans). Journal of Toxicology and Environmental Health, Part A, 67(12), 941-957. doi:10.1080/15287390490443722

Climate Change Canada. (2010). Wild species 2010: Chapter 22. Retrieved from https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/publications/wild-species-2010/chapter-22.htm.

Hayes, T. B., Collins, A., Lee, M., Mendoza, M., Noriega, N., Stuart, A. A., & Vonk, A. (2002). Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses. Proceedings of the National Academy of Sciences, 99(8), 5476–5480. doi:10.1073/pnas.082121499

Health Canada. (2011). Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Atrazine. Retrieved from https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-atrazine.html

Hoskins, T. D., & Boone, M. D. (2017). Atrazine feminizes sex ratio in Blanchards cricket frogs (Acris blanchardi) at concentrations as low as 0.1 μg/L. Environmental Toxicology and Chemistry,37(2), 427. doi:10.1002/etc.3962

Houlahan, J. E., & Findlay, C. S. (2003). The effects of adjacent land use on wetland amphibian species richness and community composition. Canadian Journal of Fisheries and Aquatic Sciences, 60(9), 1079. doi:10.1139/f03-095Koprivnikar, J. (2010). Interactions of environmental stressors impact survival and development of parasitized larval amphibians. Ecological Applications, 20(8), 2263-2272. Retrieved from http://www.jstor.org/stable/29779618

Langlois, V. S., Carew, A. C., Pauli, B. D., Wade, M. G., Cooke, G. M., & Trudeau, V. L. (2010). Low Levels of the Herbicide Atrazine Alter Sex Ratios and Reduce Metamorphic Success in Rana pipiens Tadpoles Raised in Outdoor Mesocosms. Environmental Health Perspectives, 118(4), 552. doi:10.1289/ehp.0901418

McCoy, K. A., Bortnick, L. J., Campbell, C. M., Hamlin, H. J., Guillette, L. J., & St. Mary, C. M. (2008). Agriculture Alters Gonadal Form and Function in the Toad Bufo marinus. Environmental Health Perspectives, 116(11), 1526–1532. doi:10.1289/ehp.11536

Ouellet, M., Bonin, J., Rodrigue, J., Desgranges, J., & Lair, S. (1997). Hindlimb Deformities

(Ectromelia, Ectrodactyly) In Free-Living Anurans from Agricultural Habitats. Journal of

Wildlife Diseases, 33(1), 104. doi:10.7589/0090-3558-33.1.95

Stuart, S. N.,Chanson, 1. 5., Cox, N. A., Young, B. E., Rodrigues, A. S. L., Fischman, D. L., and R. W. Waller. 2004. Status ans trends of amphibian declines and extinctions worldwide. Science 306: 1783-1786. Doi: 10.1126/science.1103538

Thurman, E., and A. Cromwell. 2000. Atmospheric transport, deposition, and fate of triazine herbicides and their metabolites in pristine areas at Isle Royal National Park. Environmental Science and Technology 34: 3079-3085.Doi: 10.1021/es000995l

Wake, D. B., and V. T. Vredenburg.(2008). Are we in the midst of the sixth mass extinction? A view from the world of amphibians. Proceedings of the National Academy of Sciences, 105: 11466-11473. Doi: 10.1073/pnas.0801921105.


Exposure to Air Pollutants and Its Association with Respiratory Illness and Asthma

Title:  Exposure to air pollutants in the San Joaquin Valley and its association with respiratory illness and asthma


 San Joaquin Valleyresidents are constantly exposed to air pollutants that can cause many health related problems such as respiratory illnesses and asthma. The objectives of my research are to first identify the sources that are exposing harmful air pollution. Secondly, to identify the toxic substance that are causing the air pollution. Third, to identify the harmful effects of air pollution on the human body. Lastly, analyzing scholarly journals, specifically about air pollution in the San Joaquin Valley, I will determine the correlation between specific air pollutants and respiratory illnesses and their effects in this region.

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 The San Joaquin Valley (SJV) population has adverse health effects and health risk from exposure to the invisible hazardous air pollutants. There is no single person from the SJV who is not exposed to the air pollution. People of all age groups have some type of health risk. High numbers of folks from the SJV seek relief and treatment at the hospital or Emergency Department (ED) from the air pollution that lingers in the region. The SJV is located in the heart of California with the population over 4 million (Ngo et al.2010). It is characterize as a flat terrain lying below 400 feet in elevation with eight counties Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare. Bordered by three mountains the California Coastal ranges, Sierra Nevada, and the Tehachapi Mountains creates air quality in this region to be very unhealthy because air pollution are trapped in the valley from every season. These counties are the agricultural center of the state and produces majority of the nations vegetables and fruits.  Agricultural productivity contributes more air pollution to the valley. Air pollution also flows in from other parts of the state like the Bay area and uncontrolled wildfires. The constant mobile sources air pollution from traffic driving along Interstate 5 and Highway 99 and the stationary sources generates even more pollutants to the SJV.

Methods & Materials

 These are the reference research methods and materials. One was studying 315 children with asthma and wheezing from Fresno and Clovis during November 2000 to April 2005. The study design uses ambient measurements from California Air Resources Board (CARB) and used statistical analysis (Mann et al.2010). The second was a sample studying 744 residents from the SJV who answered a survey during November 2014 to January 2015 from CARB, also statistical analysis statistical significance at the p  The fifth used an emission inventory, meteorology and air quality modeling that created SJV climates, andcontrol strategies to eliminate PM2.5 emissions by year 2030 (Hixson et al.2012). The last study was a climate-controlled trailer exposing young rats 10-12 weeks old to ambient particulate-matter to see the impacts on human health in the SJV (Ngo et al.2010).


 The first research was for the periods of (October to February) which is the cold season the air pollutants  Nitrogen Dioxide NO2, NO3, Particulate Matter PM2.5 peaked in the Fresno and Clovis area and the daily concentration of PM2.5 was more than the National Ambient Air Quality Standard (NAAQS) 24-hr standard/m3of 35 µg. During the periods of (April to October) which are the warm season these air pollutants Ozone O3, PM10, PM2.5 peaked and 32% of O3 concentrations were at or more than the current NAAQS 8-hr standard of 75 ppb. and the NO2 were lower than the 53 ppb NAAQS standard for the whole study (Mann et al.2010). These are the results for children who had association with air pollutions 49 children studied had allergies to cat dander, 85 children had allergies to fungi, and 47 boys with mild asthma (Mann et al.2010).


 The second research is the result of perception that participants have on air pollution quality in the SJV. The participant and characteristics are mostly 63% female and 51% 40 years of age and older, and most felt the exposure to Particulate Matter PM2.5 was a medium level 75% and a high level 19% (Cisneros et al.2017).  Only 64% view the air quality as being moderate and unhealthy and those who felt they were exposed to a lot of PM2.5 felt the air quality was bad(Cisneros et al.2017). The perception of seriousness problems in the SJV did not have air quality in the top three instead it was unemployment, crime, and obesity, and the sources of air pollution from the participants are cars and were trucks, windblown dust, and factories.

 The third research is from the correlation from the cumulative environmental hazard index,  the social vulnerability index, and the health index. Each index were at the 99% confidence level, with a coefficient of 0.296 and 0.092(Huang and London 2012). Very high concentrated populations are more vulnerable to environmental hazards and health risk. People regardless of their race or ethnicity whose socioeconomic status are low income and poor are most vulnerable to environmental and health risk.

 The fourth research shows a 25.7% of prevalence with asthma in the SJV and they were from individuals 65 years and older, currently uninsured individuals, and people who delayed care for asthma(Meng et al.2010). There was a prevalence of 9.2% for asthma related emergency department (ED) or hospital visit in the past twelve months from the  highest prevalence from children under 17 years of age, from the race and ethnicity groups of Latino, Asian/other, African-American, people from lower-income groups, and people who delayed care for asthma(Meng et al.2010). The annual average air pollutant O3 was definitely correlated with PM10 and PM2.5 there was no associated with NO2 and CO. The final results on air pollutants were only on O3, PM10, and PM2.5. From the models there was a 23% increase in O3 (95% CI 0.94 to 1.60), a 29% increase per 10ug/m3 for PM10 (95% CI 1.05 to 1.57), and a 82% increase per 10 ug/m3 for PM2.5(95% CI 1.11 to 2.98) (Meng et al.2010). ED visit among children was a 63% spike to the three air pollutants but in adults there was a 40% spike to the three air pollutants, also adults seen at the ED jumped for 30% to 60% to the air pollutants (Meng et al.2010).

   The fifth research is the predicted PM2.5concentration for 2030. A growing population means an increase in air pollution from traffic-related pollutants. Increasing vehicles traveling along Interstate 5 and Highway 99 brings more emissions adds to the massive air quality issues. Uncontrolled wildfires generate a great amount of pollutants Carbon Monoxide CO, Nitrogen Dioxide NOx, and Volatile organic compounds VOCs  making it harmful to the air quality. Control strategies were made for projection for 2030 SJV PM levels. Control C1 eliminates all emission from residential wood burning. Decrease of wood burning is because fuel consumption from home heating with higher density. Control C2 eliminated 90% of PM2.5 and 90% VOC from activities having to do with commercial meat cooking (Hixson et al.2012). Food cooking concentration increased when more people lived closer to the cooking manufactures. Control C3 diesel combustion PM to decline by 90% (Hixson et al.2012).  As people, travel more to get to where they needed such as work or school the consumption for diesel increase. Control C4 the agricultural dust will be reduce by 33% and dairy emission by 17% (Hixson et al.2012). 

 The sixth research result from the experiments shows no increases of lung cells

recovered from the rats showing there’s no immune cells from the blood to the lungs from inhaled particles(Ngo et al.2010). One experiment shows lungs with an increase in cells with exposure to fine and ultrafine particles. The results shows an  increase in interleukin in the lungs of the experimented rats who are being expose to the particles. Having a little exposure to concentrated air particles can give an increase in interleukin-6 (IL-6), a proinflammatory cytokine. Inhaled particles can affect the nonrespiratory organ like the central nervous system. Agricultural production is responsible for the regions’ air pollution especially when farmer used to burn regularly when planting season ended it added more particulate matter for the region.



 The first research, found increase of  NO2 and PM10 and PM2.5 are connected to the risk of wheeze the boys studied who has asthma. Boys with asthma had an increase to wheeze and exposures to these air pollutants NO2, PM2.5, EC, NO3, PM10 and PM2.5.  The air pollutant O3 was not greatly associated with wheezes in the analyses. In Fresno and Clovis, the main source for the air pollutant was NO2 this is a traffic-related pollution. The air pollutant NO2 can harmfully affect a child’s health especially if they are asthmatic. Exposure to NO2 increases the chance of bronchoconstrictor reaction to breathe in aeroallergen. Traffic related air pollution was one of the cause’s asthma, nitrogen dioxide (NO2). Young children diagnosis with this asthma disease may also have other respiratory illness such as bronchitis, and lung damage.


 The second research is the discussion of perception that participants have on air pollution quality in the SJV. The participants felt air pollution were really bad when the air pollution exposure levels was really high. The participants were asked to rank air pollution to other problems in the SJV air pollution was fourth on the list of seven (Cisneros et al.2017). The participant felt that the air pollution sources were from cares and truck but not agriculture emissions. Forest Fires was sixth as a serious concern for the SJV as the listed problems (Cisneros et al.2017).


 The third research indicates that combining the three index indicators that measure the environmental, social, and health conditions gives an understanding of the population that are most in need and shows the disproportion in care they receive. The result gives an understanding of the experiences that the most vulnerable populations live. Those who are low income and poor face more health and environmental risk. Through collaborative partnerships from the public environmental, environmental justice advocates, and health agencies the most vulnerable will get the help that it needs for the people from the SJV communities.



 The fourth research shows the air pollutant O3, PM10 and PM2.5 in the SJV has health effects on the people in the SJV region who have asthma. The toxic substances found in the San Joaquin Valley are among those listed in the EPA regulated Criteria air pollutants. The five outdoor air pollutants in the San Joaquin Valley are (CO, NO2, O3, PM10, and PM25). The primary air pollutants known to cause asthma and other respiratory illness are ozone O3 and particulate matter PM2.5. The secondary air pollutant found in the San Joaquin Valley are mostly during the hot spring and summer is smog. Theses air pollutants O3, PM10, and PM2.5 annual average concentrations are link to people who reported asthma symptoms or had ED visits for asthma symptoms. Children and adults show sign of having asthma issues the CHIS and air monitoring helps document it. The research can help in combating air pollution with the result found.

 The fifth research showsdiesel particle filter (DPF) will not increase NO2 or NOX emission standard for 2030 because regulation will be placed to reduce them already. The study was ran twice, the first to remove PM 2.5, and the second was to remove PM and increase the ratio of NO2 and NOx 0.1-3.5 (Hixson et al.2012). Increasing the NO2 and NOx emission will results in an increase of particle nitrate by 1% for population and 6.8% in the regional. When population increase near major roadways the projection of growth increase for people and PM2.5.


 The sixth research, the seasonal changes in air particle mass and shows some markers of inflammation and cell viability. This experiment provides an insight of how particulate matter (PM) affects the San Joaquin Valley and the health for the agricultural workers and residents who calls that region home. Most tests will be done in the future to learn more on longer exposure to OM to mimic the exposure the SJV agriculture workers and residents endure. The future focus will be on the seasonal difference of PM in the SJV and the health effect it causes.


 In conclusion, through the use of scholarly research there is a definite correlation between the San Joaquin Valley exposure to air pollutants and health related problems such as respiratory illnesses and asthma disease to its population. Evidence from different researches shows that PM10, PM2.5, O3, NO2, and CO are the main pollutants for asthma disease and cause respiratory illnesses. Air quality is a big issue in the SJV and the people in the valley must be more educated to the serious health risk that it brings to everyone off all age, sex, and race.

 To improve the SJV air quality, we must know the exact air pollutants and its source that are causing the air pollution in order to reduce it. The public and our state and federal government must work together to fight against the invisible harmful hazard and to develop more laws and regulations to combat it.


Cisneros R, Brown P, Cameron L, Gaab E, Gonzalez M, Ramondt S, Veloz D, Song A, Schweizer D. 2017. Understanding Public Views about Air Quality and Air Pollution Sources in the San Joaquin Valley, California. Journal of Environmental and Public Health, 2017, 4535142:1-7.

Hixson M, Mahmud A, Hu J, Kleeman MJ. 2012. Resolving the interactions between population density and air pollution emissions controls in the San Joaquin Valley, USA. Journal of the Air & Waste Management Association, 62(5): 566-575.

Huang G,  London J. 2012. Mapping Cumulative Environmental Effects, Social Vulnerability, and Health in the San Joaquin Valley, California. American Journal of Public Health 102(5):830-832.

Mann JK, Balmes JR, Bruckner TA, Mortimer KM, Margolis HG, Pratt B, Hammond SK, Lurmann FW, Tager IB. 2010. Short-Term Effects of Air Pollution on Wheeze in Asthmatic Children in Fresno, California. Environmental Health Perspectives, 118(10):1497–1502.

Meng Y, Rull RP, Wilhelm M, Lombardi C, Balmes J, Ritz B. 2010. Outdoor air pollution and uncontrolled asthma in the San Joaquin Valley, California. Journal of Epidemiology and Community Health. 64(2):142-147.

Ngo M, Pinkerton K, Freeland S, Geller M, Ham W, Cliff S, Hopkins L, Kleeman M, Kodavanti U, Meharg E, Plummer L, Recendez J, Schenker M, Sioutas C, Smiley-Jewell S, Haas C, Gutstein J, Wexler A. 2010. Airborne particles in the San Joaquin Valley may affect human health. California Agriculture 64(1):12-16.



Evaaluation of Prolonged Exposure Therapy

Exposure therapies are utilized to treat fear and other disorders under controlled situations. Exposure “is a key process in treating a wide range of problems associated with fear and anxiety.” (Corey, 2017, pg. 245) Controlled exposure is a systematic process between the client and a trained helping professional. During this exposure patients “confront the feared, but otherwise safe, objects, situations, thoughts, sensations, and memories with the goal of reducing fear and other negative reactions to the same or similar stimuli in the future.” (Foa, 2011) The specific kind of exposure therapy discussed in this paper is prolonged exposure therapy. (PE) In this paper I will discuss its proven scientific application making it an evidence-based practice through the details and methods used in two studies where PE is used as primary treatment. I also will discuss and how I would plan to find a connection to my own personal counseling practice as a future professional that could learn to use PE.

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Prolonged Exposure Therapy was developed by Edna Foa, PhD, the Director of the Center for the Treatment and Study of Anxiety (CTSA). The Center of the Treatment and Study for Anxiety’s website About Prolonged Exposure Therapy states that “PE has been empirically validated with more than 20 years of research supporting its use. PE is based on cognitive-behavioral principles and specially designed to help clients process traumatic events and reduce trauma-induced psychological disturbances.” (The Center of the Treatment and Study for Anxiety [CTSA], n.d.) The CTSA states that “this treatment produces clinically significant improvement in about 80% of patients with chronic PTSD. PE has been used to successfully treat survivors of varied traumas including rape, assault child abuse, combat, and motor vehicle accidents and disasters.” The CTSA website states “PE instills confidence and a sense of master, improves aspects of daily functioning, increases client’s ability to cope with courage rather than fearfulness when facing stress and improves their ability to discriminate safe and unsafe situations. In 2001, Prolonged Exposure for PTSD received an Exemplary Substance Abuse Prevention Program Award from the U.S. Department of Health and Human Services Substance Abuse and Mental Health Services Administration (SAMHSA).

In describing the PE process for individuals with PTSD, The U.S Department of Veterans Affairs website Prolonged Exposure for PTSD describes that “people with PTSD will often try to avoid anything that reminds them of the trauma, but while this can help one feel better in the moment it does not provide relief in the long term.” PE is used to help one face one’s fears, by talking about the details of the trauma and confront safe situations that one has been avoiding. In laying out treatment the website states , one can expect a provider to start by giving you an overview and getting to know more about your past. A breathing technique is taught to help manage anxiety. Around second session, the provider has to make a list of people places or activities you have avoided since your trauma, which means you will gradually confront these situations. In this practice it is hoped that in time you will feel more comfortable in these situations enough not to avoid them anymore. Then will begin an imaginal exposure, talking about trauma which can help with emotions like anger and sadness. Records of imaginal exposure can be made and listened to between these sessions. By the confrontation of the details of this trauma, you may find less unwanted memories at other times. (VA National Center For PTSD, 2019)

The VA’s treatment plan has PE lasting for 8-15 weekly sessions which is around 3 months. These sessions are 1.5 hours in length. An individual may start to feel better after a few sessions, and the benefits of PE las long after the final sessions have been completed. The VA’s PE protocol (VA National Center For PTSD, 2019) recommends that homework is done out of session to practice some of the things you have avoided since trauma. Activities are begun that are manageable working up towards challenging activities…the risks of doing PE are mild to moderate discomfort when engaging in new activities and when talking about trauma related memories. These feelings are usually brief, and people tend to feel better as they keep doing PE…most people who complete PE find that the benefits outweigh an initial discomfort.” But in an opposing way The (American Psychological Association [APA], 2019) website Prolonged Exposure (PE) describes the PE beginning exposure period in more intense language, which is to be considered. The website states about PE exposure for PSTD “This is a very anxiety-provoking for most patients, the therapist works hard to ensure that the therapy relationship is perceived to be a safe space for encountering very scary stimuli. Both imaginal and in vivo exposure are utilized with the pace dictated by the patient.”

In the first study I will discuss “Prolonged Exposure Therapy for Older Veterans With Posttraumatic Stress Disorder: A Pilot Study.” (Thorp, Stein, Jeste, Patterson & Wetherell, 2012) The purpose of this study was “to assess feasibility and efficacy of PE in older Veterans with PTSD”. Exposure Therapy had “not been studied systematically in older adults due to the published concern that these older individuals would not tolerate treatment”. Eleven men were recruited from a Veterans Affairs PTSD Clinical Team program and after assessment, eight completed prolonged exposure therapy. Study criteria included, 1) PTSD due to a military event; 2) age 55 years or older; and 3) no change in type or dosage of psychotropic medications in the past 2 months. The participants were measured on by using clinician-administered PTSD Scale 7, PTSD Scale (CAPS), The FI/12 method of categorical scoring, and summated dimensional scoring (for PTSD severity 10).

In the portion of PE therapy is this study, an author or one other psychologist provided PE14 to participants. Each of the veterans then received 90-minute sessions, twice a week totaling 6 weeks of PE. The patients were taught breathing retraining, and then created a list in hierarchical fashion of their avoided activities and other situations that were associated with the trauma. The patients were also encouraged to engage in feared activities in a systematic way outside of session and then to recount this later aloud in session. Patients listened to records of these trauma narratives between sessions. Final sessions focused on reviewing skills and creating plans to maintain treatment gains. (VA National Center For PTSD, 2019)

 In the conclusion of the study, the veterans who had completed 6 weeks of PE showed a significant reduction in clinician-rated and self-reported PTSD Symptoms. The study relays using the interpretation of CAPS scores suggested by Weathers et al.,10 as a group Veterans receiving PE showed a clinically significant decline in severity (from the extreme range to the moderate range) whereas Veterans receiving TAU (TAU consisted of medication appointments or physicians appointments to monitoring treatment and offer general support, averaging one appointment each during the 6 weeks.) did not demonstrate a clinical significant decline in severity (from the extreme range to the moderate range.) Indeed, 100% of the PE sample showed a clinically significant decline in severity whereas 40% of the veterans in the TAU sample made such a change. As the study hypothesized, that veterans with traumatic events which occurred on average 40 years earlier, still showed a significant decrease in symptoms of PTSD (clinician and self-reported) following exposure therapy.

The second study I would like to discuss about PE to demonstrate its evidence based practice is “Prolonged Exposure Therapy with Veterans and Active Duty Personnel Diagnosed With PTSD and Traumatic Brain Injury” (Wolf, Kretzmer, Crawford, Thors, Wagner, Strom & Vanderploeg, 2015) which was a study done on clinical data to analyze the effectiveness of prolonged exposure (PE) for PTSD among the veterans of Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn. These veterans all besides having PTSD had histories of mild to severe traumatic brain injury. (TBI) The data used in the study was collected from two inpatient and outpatient programs at the Department of Veteran Affairs.

In (Wolf et al., 2015) it is stated “that studies estimate that 12.0% of 17.0% of returning soldiers experience symptoms of PTSD (Seal, Bertenthal, Miner, Sen, & Marmar, 2007) and a review of Veterans Affairs (VA) health care utilization covering the last 10 years indicates PTSD was the most prevalent psychiatric disorder with approximately 217,000 cases (Seal et al., 2010). It is also estimated that of the 2.6 million soldiers deployed, approximately 253,330 experienced a TBI during their military service (U.S. Department of Defense, 2012)” The study then highlights that mental health professionals frequently encounter comorbid PTSD and TBI. (Taylor et al., 2012) Evidence based psychotherapy such as PE and cognitive processing therapy have been designated at the first line interventions for comorbid PTSD with mild TBI. (U.S. Department of Veterans Affairs and U.S. Department of Defense, 2009)

The method of this study 69 individuals received PE as part of routine care at Tampa and Durham VA medical centers. These veterans were not offered PE if they presented “psychosis, unstable bipolar disorder, imminent suicidal or homicidal ideation, and recent aggressive behavior, self-harm, or severe substance” then other mental health treatment was provided. When veterans were enlisted in inpatient treatment the average length of stay being 6 to 8 weeks, these participants completed twice weekly PE sessions. In the residential program veterans with an average length of stay of 3 to 6 months and participants were seen weekly also for PE sessions. Other forms of treatment in concurrence to PE were concurrent psychiatric medication, physiatry, cognitive rehabilitation, physical therapy and vocational rehabilitation services.

Describing the used PE treatment in all of the veterans cases the following major PE components which are listed as “(a) psychoeducation (b) repeated in vivo exposure to commonly avoided trauma-related situations and cues (c) repeated imaginal exposure to traumatic memories and (d) subsequent discussion after imaginal exposures to facilitate emotional process and corrective learning.” (Foa, et al., 2007) Which are consistent with the VA treatment manual, and no other therapy components were included. Patients that were in inpatient or residential settings completed assigned in vivo exposure independently or during community outings. Baseline measures were collecting within one week of treatment but no longer than two weeks.

Measures used in the study were the PTSD Checklist, (PCL; Weathers, Litz, Herman, Huska, & Keane, 1993) which monitored PTSD symptom severity at the initiation of PE and was used for every other session during the duration of treatment. The Beck Depression Inventory (2nd ed.; BDI-II) was also used “to measure severity of depression at the initiation of PE and every session across the course of the treatment. In results of treatment in the study there was significant and reliable clinical change. In the sample, 75.4% of the participants demonstrated reliable reduction in PTSD symptoms of 10 points or more on the PCL…and 71.6% demonstrated a reliable reduction on depression of 5 points or more on the BDI-II during treatment. The study demonstrated that these analyses show the effective ness of PE with comorbid PTSD and TBI. Due to these documented successes” (Wolf et al., 2015) noted “The findings should contribute to dispelling the notion that comorbid TBI and its associated problems represent a barrier to successful treatment of PTSD in active duty service members and veterans.”

Now I will discuss how PE may be used in my own practice as a future counselor. When I make a consideration of a serious, evidence-based practice such as PE I know it isn’t about my interpretation it is about the correct implementation. I understand that my use of it only could come through after my own professional training and then understanding. In my own theory alignment, though very much developing I want to focus on a personal empathetic connection but also, basing my practice out of evidence-based practices and methods. This would be to tailor my methods specifically to the issues I am seeing (specifically mental health.) The evidence-based treatments for specific mental illness (in whatever theory it may be based, be it CBT or Behavioral) are where I will seek more knowledge and training.

In this paper I have worked to show that PE is an evidence-based treatment for PTSD. As a noted limitation/practical issue I would keep in mind this is not the appropriate treatment for all clients with PTSD, (psychosis, unstable bipolar disorder, imminent suicidal or homicidal ideation, and recent aggressive behavior, self-harm, or severe substance) (Wolf et al., 2015) As I may see cases of PTSD in my practice, when possible I would like to see training in PE. I would especially seek this training if it was working with the veteran community or the within the VA specifically where I have considered applying for my internship. Training is offered at University of Pennsylvania Center for the Treatment and Study of Anxiety with PE’s founder Dr. Edna B. Foa, there a continuing education credit that would come with this training. Personally, I would do that if it something I could do to build my practice, I really hope to be open to learning experiences and continuing my education as a counselor always.

 The role of the counselor in this relationship performing PE I see as the helping professional. The counselor is not experiencing  the intense feelings of trauma and anxiety that the client will be facing but can only offer a genuine presence of concern and empathy. It is the counselor’s responsibility to be trained and knowledgeable about the PE process before trying it on a client as that would be very dangerous. I think there is a level of trust that needs to be built before any exposure can be started given that this will be a difficult and potentially scary process for the client. Coming back to what the APA states on their website (American Psychological Association [APA], n.d.) “This is a very anxiety-provoking for most patients, the therapist works hard to ensure that the therapy relationship is perceived to be a safe space for encountering very scary stimuli.” So, I think as a counselor it is my job to try to create that safe space. This would be by outlining the method well, talking about what may be experienced, creating an environment that is soothing.

 It would be important for me to let the client know that I am here for the duration of this journey, and together we can enable the client to discover they can face the trauma they may not have been able to until the exposure therapy process. Relationship issues that may be encountered are this would be an increased time of need for the client where I may have to be more open to outside communication, if they are doing out of session exposure. I would also have to consider the workload and relationships of my other clientele and being present for them. This exposure time and the increased anxiety/emotional component that may come out of clients may need to be a time of greater self-care out of work for myself.  

From a diversity perspective on PE  (Corey, pg. 259, 2017) lists exposure therapy as a behavior therapy and in which “behavior therapists need to become more responsive to specific issues pertaining to all forms of diversity. Because race, gender, ethnicity, and sexual orientation are critical variables that influence the process and outcome to therapy…it is essential for therapists to conduct a thorough assessment of the interpersonal and cultural dimensions of the problem.” I think a lot of this would come in the investigative part of this therapy, where and when the trauma developed. How others in this individual’s home and other areas such as their partners and family may need to be involved in the treatment. It is possible that sessions would have to be done not just with the individual but having other family come into talk about the process. Coming out of Feminist Theory how one’s own formed cultural identity, and gender role messages (such as if the client identified as a man thinking he should be tough and bury trauma) play into part. Investigating any societal messages related to how one is supposed to behave after experiencing trauma if it is something to hide or be open about in one’s specific cultural household.

In conclusion I hope to have properly introduced prolonged exposure therapy (PE) and inform how it is indeed an evidence-based practice with a strong history and evidence of support. Its method is impactful and proven successful, with its 20 plus years of application in those with traumatic events and traumatic induced mental illnesses, and specifically addressed in this paper example studies veterans working with PTSD. As a future counselor I hope to learn PE’s correct methodology and implication though proper training and have PE something I can offer my clients. It was engaging and informative to learn about the details of this evidence-based practice and I hope to learn more about exposure therapy in the future.


American Psychological Association. (2019). Prolonged Exposure (PE). Retrieved from https://www.apa.org/ptsd-guideline/treatments/prolonged-exposure

Beck, A. T., Steer, R. A., & Brown, G. K. (1996). Beck Depression Inventory Manual. San Antonio TX: The Psychological Corporation.

Center for the Treatment and Study of Anxiety. (n.d.) About Prolonged Exposure Therapy. Retrieved from https://www.med.upenn.edu/ctsa/workshops_pet.html

Corey, G. (2017). Theory and practice of counseling and psychotherapy. Boston, MA: Cengage Learning.

Foa, E. B., Hembree, E. A., & Rothbaum, B. O. (2007). Prolonged exposure therapy for PTSD: Emotional processing of traumatic experiences, therapist guide. Oxford, England: Oxford University Press.

Foa, E. B. (2011). Prolonged exposure therapy: past, present, and future. Depression and anxiety.

Seal, K.H., Bertenthal, D.S., Miner, C.R., Sen, S., & Marmar, C.R. (2007). Bringing the war back home: mental health disorders among 103,788 US veterans returning from Iraq and Afghanistan seen at Department of Veterans Affairs facilities. Archives of internal medicine, 167 5, 476-82 .

Seal, K. H., Maguen, S., Cohen, B., Gima, K. S., Metzler, T. J., Ren, L., . . . Marmar, C. R. (2010). VA mental health services utilization in Iraq and Afghanistan veterans in the first year of receiving new mental health diagnoses. Journal of Traumatic Stress, 23, 5–16. doi:10.1002/jts.20493

Taylor, B. C., Hagel, E. M., Carlson, K. F., Cifu, D. X., Cutting, A. B., Douglas, E., & Sayer, N. (2012). Prevalence and cost of co-occurring traumatic brain injury with and without psychiatric disturbance and pain among Afghanistan and Iraq war Veteran VA users. Medical Care, 50, 342–346. doi:10.1097/MLR.0b013e318245a558

The U.S Department of Veterans Affairs National Center For PTSD. (2019) Prolonged Exposure for PTSD. Retrieved from https://www.ptsd.va.gov/understand_tx/prolonged_exposure.asp

Thorp, S. R., Stein, M. B., Jeste, D. V., Patterson, T. L., & Wetherell, J. L. (2012). Prolonged exposure therapy for older veterans with posttraumatic stress disorder: A pilot study. The American Journal of Geriatric Psychiatry, 20(3), 276-280.

U.S. Department of Veterans Affairs and Department of Defense (VA/DoD). (2009). VA/DoD clinical practice guideline for management of concussion/ mild traumatic brain injury. Washington, DC: Author. Retrieved from http://www.healthquality.va.gov/mtbi/concussion_mtbi_full_1_0.pdf

U.S. Department of Defense. (2012). U.S. military casualty statistics: Operation New Dawn, Operation Iraqi Freedom, and Operation Enduring Freedom. Washington DC: Author. Retrieved fromhttp://www.fas.org/sgp/crs/natsec/RS22452.pdf

Weathers, F. W., Litz, B. T., Herman, D. S., Huska, J. A., & Keane, T. M. (1993, October). The PTSD Checklist: Reliability, validity, and diagnostic utility. Paper presented at the Annual Meeting of the International Society for Traumatic Stress Studies, San Antonio, TX.

Wolf, G. K., Kretzmer, T., Crawford, E., Thors, C., Wagner, H. R., Strom, T. Q., … & Vanderploeg, R. D. (2015). Prolonged exposure therapy with veterans and active duty personnel diagnosed with PTSD and traumatic brain injury. Journal of Traumatic Stress, 28(4), 339-347.


Currency Exposure to Hedging Currency Risks

Hedging Currency Risks at AIFS, we shall now address the many stipulations regarding issues such as currency exposure and hedging decisions of the AIFS Company. Looking at the theory and practices of Archer-Lock within the company, with the information given we shall now analyze and interpret the report of AIFS. Using the financial Instruments of the foreign exchange market, the effect these instruments have on hedging will further be discussed, as well as the result of these instruments on the hedging decision.

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It is important to note that Becky Tabaczynski, CFO for the group’s high school travel division ACIS, portrayed the idea a good hedging result is gained due to good relationships across the board. Whilst in some companies, hedging is considered a financial decision, independent of the business needs – here; we’re trying to match the business needs. Now with the information provided in the case study, combined with knowledge of hedging options, the topic of currency exposure will be discussed.
Q1. What gives rise to the currency exposure at AIFS?
Currency exposure is the extent to which the future cash flows of an enterprise, arising from domestic and foreign currency denominated transactions involving assets and liabilities, and generating revenues and expenses are susceptible to variations in foreign currency exchange rates (International Federation of Accountants, 2010).
Currency exposure at AIFS can be caused by 3 risks: the bottom-line risk, volume risk and competitive pricing risk. These 3 risks happen at AIFS because of the AIFS’s hedging policies, so before analysing these 3 risks it is necessary to analyse AIFS’s hedging policies.
AIFS’s Hedging Policies
AIFS starts to hedge foreign currencies between 6 months and 2 years before the main pricing date, and uses forward contracts and currency options to hedge currency; the main hedging technique is forward contracts. Then AIFS uses these currencies to pay its customers’ expense abroad. AIFS charges USD by “catalogue-based” price from its customers, so no matter how the exchange rates change in the spot market, AIFS never changes its price in that period.
AIFS uses forward contract to hedge before it has completed its sales cycle. So AIFS has to predict its business then hedge based on its prediction, but the situation that the number AIFS pays equals to the number AIFS buys is very hard to carry out. When the currencies that AIFS has bought are smaller than it has to pay, AIFS has to buy some more currencies by using currency options. When the currencies it has bought are greater than it has to pay, currency exposure happens.
The Bottom- Line Risk
Exchange rate is always fluctuant. EURO is one of the main currencies that AIFS needs to hedge. Looking at the graph, the exchange rate between USD and EURO in January was highest in 2010, which was 1.427$/€, and the exchange rate in June was the lowest, which was only 1.221$/€, the difference between highest and lowest is 0.206€/$, so when purchasing large amounts of EURO by using USD, the large difference of price will appear. The main hedging technique of AIFS is forward contracts, so if the exchange rate at the contract date is higher than the exchange rate at the settlement date, AIFS is at a disadvantage (maybe AIFS can choose currency options at this time, but it needs to pay premium, so the cost may be not reduced so much). When this situation happens, AIFS’s cost will be higher and it will lose profit.
2010- American Dollars to 1 EUR
Average Rates
1.42721 USD (20 days average)
1.36857 USD (20 days average)
1.35685 USD (23 days average)
1.34095 USD (21 days average)
1.25653 USD (21 days average)
1.22085 USD (22 days average)
1.277 USD (22 days average)
1.29029 USD (21 days average)
1.3067 USD (22 days average)
1.38978 USD (21 days average)
1.38806 USD (12 days average)
From X- rate.com, 2010
The Volume Risk
When AIFS uses forward contract to hedge currencies, it doesn’t know the number of customers it will get in this period. AIFS has been doing culture and educational exchanges for more than 40 years and got a very good praise and has a large number of customers, every year many young people go abroad via AFIS. Because it’s so popular, it’s hard to say how many customers will be increased next time. Also, war, terrorism and policies and other uncertainties will affect people’s mind, these factors will make more people prefer to stay at home rather than go abroad, and in that case the number of customers will be decreased. So it’s hard to predict the number of customers, it’s hard to say whether the number of customers will increase or decrease. In negative situations where there will be a lack of customers, the foreign currencies that have been bought will not be used; this is when currency exposure is evident.
The Competitive Pricing Risk
When AIFS is purchasing and using currencies, its competitors are doing it as well. These companies may contract with banks in lower exchange rates, which makes their charges lower than AIFS and therefore makes AIFS less competitive. Customers may buy currencies from other companies, and so AIFS’s currencies can’t be sold up and currency exposure happens.
The changes of transportation fees (like train, boat, plane ticket), living fees, hotel fees can also give rise to the currency exposure. When these fees reduced, AIFS will pay less and may not use all of the currencies it has bought.
According to AIFS’s hedging policies, it has to predict the exchange rate fluctuant, the number of customers, which may be different with the final exchange rate and the volume when selling currencies, so the currency exposure happens. The actions of AIFS’s competitors may make AIFS less competitive resulting in minimum sales of the currencies bought, further resulting in currency exposure. So the bottom-line risk, the volume risk and the competitive pricing risk will give rise to the currency exposure at AIFS. Also, the changes of fees may cause currency exposure.
Q2. What would happen if Archer-Lock and Tabaczynski did not hedge at all?
According to the case, The American Institute for Foreign Students (AIFS) organizes students who study abroad and the cultural exchange programs. It has two major divisions which are Archer-Lock managed The Study Abroad College and the High School Travel division, whose finances Tabaczynski managed. The problem faced by AIFS is the revenues of the company are mainly in US dollars, but most of their costs are in British pounds and Euros. AIFS sets guaranteed prices for its exchanges before its final sales figures are known. Therefore, for AIFS, the foreign exchange hedging is the key important area. The managers use currency hedging to protect their bottom line and cope with changes in exchange rates. But if Archer-Lock and Tabaczynski did not hedge at all, it would mean full exposure to the currency risk, the company could lose a lot of money if USD depreciated.
Maybe the company can produce good results and have a really good profit when the USD appreciated if they did not hedge at all, as there are no other losses to erase their total revenue. However, they cannot know what the future sales volume and future exchange rate are, and so they may need to face losing a tremendous amount of money if USD depreciated. The cost base of the company would increase, and the revenues in USD will remain the same, this means their profitability would be erased. Also, AIFS needs to preserve their price guarantee policy. If they did not hedge at all, the company may incur losses by following this policy. Moreover, there may be a difference between final sales volumes and projected sales volume, and this exposes the company to having either more or less of the foreign currency depending on the final sales volume. For instance, as we know from the case, every year AIFS expected 25,000 students in their project. If the currency exchange rate decreased to USD 1.01/EUR, the company could save USD 5.25 million, however, if the exchange rate increased to USD 1.48/EUR, the company lose USD 6.5 million.
Q3. 100% hedge with option and 100% hedge with forward
The data shows above, When 100% hedge with option, currency rate 1.01, and the outcome is higher than total cost, the company can gain the profit. Rate becomes to 1.22 and 1.48, the outcome is lower than total cost, and the company has risk and a loss of money. When 100% hedge with forward, the fixed rate is locked in 1.22, the outcome is 0. That is means no risk and no profit.
Q4. Using the forecast final sales volume of 25,000, the following are the possible outcomes relative to the ‘zero impact’ scenario described in the case.
Zero impact happened with rate (1.22) when they use forward contract were the same as project costs. When dollar becomes weak (1.48) it would cause a negative impact by a loss of money. When dollar becomes strong (1.01) it would cause a positive impact through gain of profit.
When the USD is strong (1.01), the more options there are to hedge, the lower the cost. When USD is weak (1.48) the more options there are to hedge, the more the cost.
Q5) what hedging decision would you advocate?
Should we not hedge at all?
As AIFS guaranteed its prices would not change before the next catalogue, if the USD goes weak, AIFS need to more USD to pay for its overseas cost¸ however the price cannot be changed, which means AIFS will lose money. To eliminate this risk, AIFS better hedge.
What do you advocate?
(Advantages and Disadvantages)
The forward contract is a simple arrangement widely used by the companies to manage the exchange rate risk. It can guarantee the amount of currency AIFS would receive in the expiry date of the contract, so it can get larger profits with forward contracts if AIFS count on a favourable exchange rate. The company can also avoid the 5% option premium, but it is not easy to get the counter party who would agree to fix the time period and the future exchange rate which would result in illiquidity. Thus being bilateral private contracts, the forwards have to be executed.
The option contract can eliminate the downside risk and being more flexible, it can be seen as a combination of covered interest arbitrage depending on the difference in currency options and interest rates; it gives the company the right to sell or purchase a currency at an agreed exchange rate, but not the obligation. With the option contracts AIFS can hold the currency until the favourable exchange rate arises, so it would be more secure for the company. However, the premium cost is the disadvantage of option, and it has to be paid up front.
Both forward contract and option contact work if the company is tight on cash and cannot spend 5% option premium – in this case the forwards contract is a better choice. However, if AIFS has sufficient funds and foresees changes in exchange rates, then it should use option. AIFS does not have to exercise the contract when currency moves to unfavourable exchange rates.
What happens if sales volumes are lower (10000) or higher (30000) than expected (25000)?
According to appendix 3 and 4:
The sales volume increase to 30000, exchange rate is 1.01. AIFS Company can gain the profit. Exchange rate is 1.22 and 1.48, AIFS Company exist risk loss the money; but when use 100% forward to hedge Company can avoids risk and there is no profit.
The sales volume is decrease to 10000, the total cost is 1000* 10000= €10000000
There are 3 possible situations that will happen at this time.
= 0.4 = 40%
According to the calculation above, when AIFS’s currency hedge is covered less than 40% of its prediction (it predicts 25000 sales volumes), AIFS needs to buy some more currency to reach €10000000 by using spot trading rate; when AIFS’s currency hedge is covered at 40%, the currency it buys is equal to €10000000; when the currency hedge covered over 40%, AIFS can’t use all of the EUR it has bought, so AIFS has to sell the extra EUR or save them and use them in the next period.
Source: AIFS case
There will be 4 outcomes with the ‘in the money’ and ‘out of money’ positions and high and low sales volume (30000 or 10000).
Square 1 shows low sales volume (10000) with strong USD that when the company is out of money (1.01USD/EUR). AIFS has an excess of currency. In this case, if it locked into surplus forward contracts then it would lose money. So the option contract is more favourable. AIFS does not execute the contract, it just lets it expire.
In square 2 shows low sales volume (10000) with weak USD, The requirement of the currency is below the projection (25000), and the exchange rate is high (1.48USD/EUR). If AIFS uses forward contract the gain is larger compared to when it uses options contract because the options contract costs 5% of the nominal USD strike price.
In square 3 the exchange rate moved out of money (1.01USD/EUR) and the sales go higher (30000) than expected. So AIFS doesn’t have to buy euro at higher rate, therefore, the Options contract is better, as the extra volume they need (5000), can be bought at the spot rate. The increase of the Spot and Fixed rates and the difference of the volume of sales are the reason for company loss.
The tricky square 4 shows when the exchange rate moved in the money (1.48 USD/EUR) and AIFS’s sales volume came in higher (30000) than projections, which means the company need more currency (5000), however, the exchange rate is high. In this case, Forward contracts should be used and the extra volume at the spot rates should be bought. The increase of sales may offset the downside.
For companies that work with more than one currency, several hedging techniques are available to guard against foreign exchange fluctuations. After studying and addressing the case study of AIFS, it can be concluded that the changes in fees can be the cause to currency exposure. The fact that the company’s revenues are in USD, and costs in GBP and Euro’s may result in a rise to currency exposure. After analyzing the affects of financial instruments such as forward and option contracts will have on the company, it has been decided that the company would be at a better advantage with Forward contract in order to prevent risks. AIFS charges USD by “catalogue-based” prices from its customer, and as the company guaranteed the prices will not change, if the rate of the USD decreases then the company will be at a loss as they will have to cover other expenses with the currency they have bought, and in order to prevent this risk, the company would be in a better position if they hedged.
International Federation of Accountants, 2010,
[Accessed on 4/11/2010]
X-rate.com, 2010, http://www.x-rates.com/d/USD/EUR/hist2010.html [Accessed on 16/11/2010]

Effect of Light Exposure on a Plants Stomata Mechanism



   Plant transpiration refers to evaporation from plant tissue (Kubota, 2016), specifically while the stomata are open for the passage of Co2 and O2 during photosynthesis. (Transpiration, 2011) Stomata are microscopic pores found on the epidermis of plants. Though most stomata are found on leaves, they can be found on all aboveground parts of a plant. These pores allow the exchange of gases between the outside environment and the air canals within a plant. These pores play a critical role in the process of photosynthesis, and can open and close as a response to environmental conditions. (Maximum, 2018)

   Plant transpiration is, more or less, an invisible process. (Perlman, 2016) The process of plant transpiration is affected by Light, Temperature, Humidity, Wind, and Soil Water. The listed variable will affect the transpiration cohesively and independently:

The more light the more transpiration; Warmer temperatures will increase transpiration; Humidity effects the rate of diffusion; Dryer air increases transpiration; Increased wind dries surrounding air which increases transpiration; Water loss increases transpiration. Extended water loss will cripple transpiration process causing the plant to wilt. (Transpiration, 2011; Transpiration, 2018)

   Within this experiment, the transpiration through different light exposure variables will be measured. If the tested plant species is exposed to more light under a controlled level of moisture, then the plant species transpiration level will increase due to the result of the light stimulating the opening of the plants stomata mechanism. The following light exposure variables will be tested, Constant Light (light source will be shined through filter to keep heat from light effecting plant moisture), No Light (After 24 hours of no light, the transpiration will be measured), Half-Light/Half-Dark (After 24 hours of half-light and half-dark exposure, the transpiration will be measured), and normal light from natural environment by window. The goal of this experiment is to determine what the plant’s preferred environment consists of regarding light exposure. The more inclusive methodology would also include different light color filters throughout the light exposure variables to determine if color of light exposure also had an effect on the plant transpiration. Additionally, it is very important to keep the controls across the experiment to reflect the most dependable results of plant transpiration.



   The experiment took three days to complete to measure plant transpiration. The materials accounted for and the environments of normal light, continuous light, no light, and half-light/half dark were established and maintained for a 24 hour time frame.

   A tub was filled with store bought water to fill tubing with the GPS attachment utilizing a syringe to ensure no air bubbles are in the tubing. Following this, a closable valve attachment was connected to one end and set in the closed position. The plant was cut with a razor at a 45° angle to prevent any crushing of the plant’s stem and was inserted into the tubing as far as it would go, and then a clamp was applied to the tubing where the plant was inserted. The plant and tubing were removed from the water. Petroleum jelly was applied to the area where the plant was inserted into the tubing to create an air tight seal. The GPS was attached to the valve end of the tubing. The tubing with plant and GPS was setup on the stand with the GPS at a higher elevation on the stand. The GPS was then connected to the LabQuest 2 and the data was collected.

   Through the experiment, the variables were maintained to include the continuous light variable which was created shining light through water to prohibit heat exposure from effecting the plant’s transpiration. The captured transpiration data was transferred to a computer using a USB cord from the LabQuest2 device into LoggerPro3 program. All steps were repeated three times through each trial.



   The initial experiment involved the normal light variable. The first trial exhibited an initial kPa of 102.9 with a final kPa of 100.7. Through the first five minutes of readings the kPa decreased at an average of 0.23 kPa per minute. Through the final five minutes the kPa decreased at an average of 0.15 kPa. The average kPa through the trial was 0.19 kPa per minute. The Normal Light Trial 1 graph exhibits the gradual dissention of kPa through the first trial. The second trial exhibited an initial kPa of 103.15 with a final kPa of 101.9. Through the first five minutes of readings the kPa decreased at an average of 0.20 kPa per minute. Through the final five minutes the kPa decreased at an average of 0.10 kPa. The average kPa through the trial was 0.15 kPa per minute. The Normal Light Trial 2 graph exhibits the gradual dissention of kPa through the second trial. The third trial exhibited an initial kPa of 117.5 with a final kPa of 115.7. Through the first five minutes of readings the kPa decreased at an average of 0.28 kPa per minute. Through the final five minutes the kPa decreased at an average of 0.11 kPa. The average kPa through the trial was 0.21 kPa per minute. The Normal Light Trial 3 graph exhibits the gradual dissention of kPa through the third trial. The combined three trials exhibited an average starting kPa of 107.85 and an ending kPa of 106.1 with an average kPa dissention of 0.15 kPa.

Normal Light Trial 1


Normal Light Trial 2

Normal Light Trial 3

Normal Light Combined Trials 1, 2, 3

   The next experiment involved the no light variable. The first trial exhibited an initial kPa of 100.695 with a final kPa of 100.5. Through the first five minutes of readings the kPa decreased at an average of 0.028 kPa per minute. Through the final five minutes the kPa decreased at an average of 0.039 kPa. The average kPa through the trial was 0.036 kPa per minute. The No Light Trial 1 graph exhibits minimal kPa through the first trial. The second trial exhibited an initial kPa of 100.63 with a final kPa of 100.44. Through the first five minutes of readings the kPa decreased at an average of 0.026 kPa per minute. Through the final five minutes the kPa decreased at an average of .012 kPa. The average kPa through the trial was .019 kPa per minute. The No Light Trial 2 graph exhibits minimal kPa through the second trial. The third trial exhibited an initial kPa of 100.69 and a final kPa of 100.69. Through the first five minutes of readings the kPa increased to a kPa of 100.82 and then returned to the initial kPa of 100.69. Through the final five minutes the kPa once again increased to a kPa of 100.82 and then returned to the initial kPa of 100.69. The No Light Trial 3 graph exhibits the mirrored display of increasing kPa and decreasing kPa within the trial. The combined three trials exhibited an average starting kPa of 100.67 and an ending kPa of 100.54 with an average kPa dissention of 0.15 kPa.

No Light Trial 1

No Light Trial 2

No Light Trial 3

No Light Combined Trials 1, 2, 3

   The next experiment involved the Continuous Light variable. The first trial exhibited an initial kPa of 128.0 with a final kPa of 123.0. Through the first five minutes of readings the kPa decreased at an average of 0.55 kPa per minute. Through the final five minutes the kPa decreased at an average of 0.25 kPa. The average kPa through the trial was .08 kPa per minute. The Continuous Light Trial 1 graph exhibits a higher kPa with minimal dissention. The second trial exhibited an initial kPa of 100.6 with a final kPa of 101.1. Through the first five minutes of readings the kPa increased at an average of .028 kPa per minute. Through the final five minutes the kPa started and ended at a kPa of 101.1 with minimal activity. The average kPa through the trial was an increase of 0.38 kPa per minute. The Continuous Light Trial 2 graph exhibits the increase of kPa through the second trial. The third trial exhibited an initial kPa of 100.95 with a final kPa of 100.6. Through the first five minutes of readings the kPa decreased at an average of 0.06 kPa per minute. Through the final five minutes the kPa decreased at an average of 0.02 kPa. The average kPa through the trial was .008 kPa per minute. The Continuous Light Trial 3 graph exhibits minimal dissention of kPa through the third trial. The combined three trials exhibited an average starting kPa of 109.85 and an ending kPa of 108.23 with an average kPa increase of 0.041 kPa.

Continuous Light Trial 1

Continuous Light Trial 2

Continuous Light Trial 3

Continuous Light Trial 1, 2, 3

   The final experiment involved the Half-Light/Half-Dark variable. The first trial exhibited an initial kPa of 100.63 with a final kPa of 100.63. Through the first five minutes of readings there was no change in kPa. Through the final five minutes the kPa showed no change in kPa. The average kPa through the trial was 0.00 kPa per minute. The Half-Light/Half-Dark Trial 1 graph exhibits minimal kPa with no ultimate change in kPa at the minute measurement points. The second trial exhibited an initial kPa of 100.7 with a final kPa of 100.4. Through the first five minutes of readings there was no change in kPa. Through the final five minutes the kPa decreased at an average of .04 kPa. The average kPa through the trial was .02 kPa per minute. The Half-Light/Half-Dark Trial 2 graph exhibits minimal kPa through the second trial. The third trial exhibited an initial kPa of 100.7 and a final kPa of 100.42. Through the first five minutes of readings there was no change in kPa. Through the final five minutes the kPa decreased at an average of 0.052 kPa. The average kPa through the trial was .02 kPa per minute. The Half-Light/Half-Dark Trial 3 graph exhibits minimal dissention of kPa through the third trial. The combined three trials exhibited an average starting kPa of 100.68 and an ending kPa of 100.48 with an average kPa dissention of 0.013 kPa.

Half Light / Half Dark Trial 1

Half Light / Half Dark Trial 2

Half Light / Half Dark Trial 3

Half Light / Half Dark Trials 1, 2, 3



   The experiment’s results supported the original hypothesis if the tested plant species is exposed to more light under a controlled level of moisture, then the plant species transpiration level will increase due to the result of the light stimulating the opening of the plants stomata mechanism. The plant used was a common plant known as Devil’s Ivy which had durable stems to insert into the tubing. The following are the overall results for the variables tested. The combined three trials of the Normal Light variable exhibited an average starting kPa of 107.85 and an ending kPa of 106.1 with an average kPa dissention of 0.15 kPa; the combined three trials of the No Light variable exhibited an average starting kPa of 100.67 and an ending kPa of 100.54 with an average kPa dissention of 0.15 kPa; the combined three trials of the Continuous Light variable exhibited an average starting kPa of 109.85 and an ending kPa of 108.23 with an average kPa increase of 0.041 kPa; and the combined three trials of the Half-Light/Half-Dark variable exhibited an average starting kPa of 100.68 and an ending kPa of 100.48 with an average kPa dissention of 0.013 kPa. The results prove more light does stimulate transpiration. Additionally, the Continuous Light variable yielded the highest kPa. The Normal Light variable was only 2.0 kPa less of a starting point and ended on approximately the same dissention of kPa as the Continuous Light variable. The No Light variable exhibited the least amount of transpiration proving light is a necessity to stimulate the transpiration process. The Half-Light/Half-Dark variable is not reliable as the testing was completed immediately following the 12 hours of dark. A better test would have been to do another variable of Half-Light/Half-Dark and immediately test the kPa following the 12 hours of light. Moreover, a more inclusive variable should have included a strobe light variable to test the effects of rapid light intervals on the plant’s transpiration.

   Lastly, the experiment supported the testing administered to include different trials and supported results. Corrections for future experiments and research should include altitude differential, temperature changes, moisture changes, color filters, etc. Including these more extensive variables could prove the likeliness to determine ultimate transpiration requirements which could bode better plant production. Also, it would be smart to do several different full experiments including different plant species due to the fact different plants require different elements to thrive in their environments.


Air Pollution Exposure & Dose in Children Travelling to School by Bus

Research Proposal






Children travelling in school buses are subjected to cumulative air pollutants within the bus-cabin, which effects their health. In this proposed study, a comparison of exposure of air pollutants (carbon monoxide and ultrafine particles) among the children inside the school-bus with surrounding ambient air and children travelling by other non-school buses will be determined. The average exposure to these pollutants along with duration will be calculated and compared with inside school bus, non-school buses and surrounding outside ambient air. This comparative study will further help in determining the dose- response relationship of air pollution exposure among the school children along with its health impact.



Recent data released by the World Health Organization (WHO) show that air pollution has a vast and terrible impact on child health and survival. Globally, 93% of all children live in environments with air pollution levels above the WHO guidelines. More than one in every four deaths of children under 5 years is directly or indirectly related to environmental risks. Both ambient air pollution (AAP) and household air pollution (HAP) contribute to respiratory tract infections that resulted in 543,000 deaths in children under 5 years in 2016. As children experience the consequences of air pollution in special, specific ways, they deserve to be assessed in a special way.

Children are at greater risk than adults from the many adverse health effects of air pollution, owing to a combination of behavioural, environmental and physiological factors. Children are uniquely vulnerable and susceptible to air pollution, especially during fetal development and in their earliest years. Their lungs, organs and brains are still maturing. Their lungs, are rapidly developing and therefore more vulnerable to inflammation and other damage caused by pollutants. They breathe faster than adults, taking in more air and, with it, more pollutants. Children breath closer to the ground level, where some pollutants reach its peak concentrations.

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Recent data published by the World Health Organization (WHO) show that air pollution has a huge and terrible impact on the health and survival of children. Globally, 93% of all children live in environments with air pollution levels that exceed the WHO guidelines. More than one death in four of children under the age of 5 is directly or indirectly related to environmental risks. Both air pollution (AAP) and domestic air pollution (HAP) contribute to respiratory tract infections that caused 543,000 deaths in children under the age of 5 in 2016. How children experience the consequences of Air pollution in special and specific ways deserves to be evaluated in a special way.

Children are at greater risk than adults of the many adverse health effects of air pollution, due to a combination of behavioural, environmental and physiological factors. Children are particularly vulnerable and susceptible to air pollution, especially during fetal development and in the early years. Their lungs, organs and brain are still maturing. The lungs are developing rapidly and, therefore, they are more vulnerable to inflammation and other damage caused by contaminants. They breathe faster than adults, absorb more air and, with it, more pollutants. Children breathe closer to ground level, where some pollutants reach their maximum concentrations

Urban air pollution is one of the most serious problems faced by the people across the urban centres of the world. Epidemiological research suggests that health of the humans is impacted by air pollutants causing chronic disease in pulmonary and respiratory infections (Hildebrandt K, 2009)(Weinmayr G, 2010)(Künzli N, 2000). Standards prescribed for different air pollutants in the ambient air are usually based on the risks posed to adults. Sensitivity of air pollutants in children is compromised when designing and implementing air pollutant standards.

A health survey conducted by the new Zealand’s Ministry of Health reported that, one in eight adults and one in seven children have asthma due to increase in urban air pollution (Source: New Zealand Health Survey). Children with bronchitis have increased to more than half, from 3984 in 2000 to 6,320 in 2017 (Barnard & Zhang, 2018). This is due to their high inhalation

rate and lung surface area with respect to body weight which makes them more susceptible to air pollution (Dockery, Speizer 1989; Lipsett,1995; Thurston, 2005). They are also at a higher risk of being affected by air pollutants as they have lower immune system (Dockery, D.; Speizer, F; 1989; Lipsett, M; 1995; Thurston, G. D., 2005; Wallace, L. A, 1991; Flachsbart, 1995), increased risk in triggering asthma, decreased lung functioning, blood cancer and increase in susceptibility to lung infections (Bennett and Zeman, 1998).

Further, Sustainable Development Goals (SDGs) recognize the importance of social and environmental factors as determinants of health. All the SDGs are clearly linked to health-related targets, reflecting the growing awareness that health, environmental and poverty alleviation are interconnected –that ensuring healthy lives for all (SDG 3) and making cities inclusive, safe, resilient and sustainable (SDG 11) require universal access to energy (SDG 7) and hinge upon combating climate change (SDG 13). The launch of the 2030 Agenda for Sustainable Development offers an unparalleled opportunity to increase action to address the environmental hazards that undermine children’s health. Implementing evidence-based policies and health practices to protect children from air pollution will, in turn, be essential to realizing the Sustainable Development Agenda: reducing children’s exposure can have enormous benefits due to avoided disease, reduced mortality and improved well-being. Reducing air pollution can also improve health and well-being by slowing climate change.

One of the main contributors of air pollution exposure in children is during their commute to school in a school bus (Behrentz & Sabin, 2005; Wu &Delfino, 2005; Behrentz, Kozawa, 2005; Rea, Zufall, 2001). Studies show that the air pollutant concentration inside the bus cabin is far higher than that of the ambient air outside the bus. Children are exposed to various irritants and substances from vehicle exhaust from bus idling and accumulated pollutants inside the bus cabin along inflow of traffic pollutants. Air pollutants concentrations inside a school bus can be 10 times higher than the background ambient levels (Shikiya et al.,1989; Chan et al., 1991; Lawryk et al., 1996). The on-road UFP concentrations typically range from 10,000 to 500,000 particles/cm3 (Zhu et al., 2007), one or two orders of magnitude higher than typical ambient levels in an urban environment.

Further, Diesel fuelled school buses pose a 23-46 times higher cancer- risk to children when compared to the standards set by the Government (Solomon et al., 2001). As per a report by the Ministry of Transport on Bus Safety in New Zealand, the age limit for a school bus is 26 years and that of a non-school urban bus is 20 years. This shows that the service provided by the school bus is longer than that of a non-school bus.  The accumulation of pollutants inside the bus cabin highly depends on the age and service of the bus which can be of a higher risk to children. Even though children may spend only few hours per day on school buses, the high levels of exposure encountered on-board school buses can add considerably to their daily and annual exposures to air pollutants

Self-pollution of the bus is one of factors that causes in-cabin air pollution (Fitz et al., 2003).  damage or cracks in the crankcase or exhaust system will collect diesel emission in the school bus, as it is more common not check/ regularly maintain the engines as much as the regular buses (Behrentz, 2004; Adar, 2008). As per studies, the concentrations of pollutants inside the cabin is double the amount than roadway concentrations & 4 times higher than ambient concentrations (Beatty & Shamshik, 2011). It is also observed that the Particulate matter & air toxins concentrations are 12 times higher than ambient pollutant levels (Wargo, 2002; Sabin, 2005).

Fig 1: Depiction of concentration of UFPs considerably higher than PM 2.5 concentration inside motor vehicles in various cities from Xu, Bin & Chen (2016)

Apart from the above, the accumulation of pollutants from other vehicles inside the closed compact bus is important to explain variability of on-board concentration (Rodes and Sheldon, 1998). However, the pollution of the vehicular exhaust itself will result in accumulation of pollutants inside the bus (Marshall & Bentertz,2005). The above analysis suggests that efforts to reduce air pollutant needs to be addressed as children are exposed to it throughout their school years, when they are the most susceptible (Dirks & Salmond, 2018)


The identification of assessment of Air pollution exposure and its health impact helps to understand the reasons for divergent opinion, without which it will be difficult to develop effective policies. For various reasons, the magnitude of the health problem from exposure to urban air pollution needs to be estimated. Assessment of Dose- Response function is not just a tool for improving our understanding of environmental and health linkages, but it also allows estimates from different sources to be compared and communicated in a standardized format, which supports decisions on priority actions to be undertaken in health and the environment sector. This also helps for prioritizing actions to be taken, when planning to prevent or reduce problems associated with a high disease burden and those preventive actions can be used as input for infrastructure planning.

Further, the aim of this proposed research is to measure the in-cabin air pollution concentration in a school bus and compare the same with the surrounding ambient air quality and with pollutant concentration of non-school buses. The pollutants considered for the proposed study are ultrafine particle counts and Carbon Monoxide concentrations. The study is to be conducted through travelling voluntarily in a school bus to-and-from a specific route designed and measuring the air pollutant concentration exposure on school children.

Such studies have not been conducted in Auckland and will give a clear picture on the in-cabin pollution exposed to school children. If the pollutant concentration is exceeding the ambient air quality standards, alternatives solutions in reduction of the pollutant exposure to children can be drawn from this study. This study will also help in reducing the vulnerability of a school child in contracting various health disorders.


Methods and materials

Study site

A specific route is selected as per the Auckland Transport school bus routes in consideration with the school zone area. Newmarket, an Auckland suburb to the south-east of the central business district is preferred. A total of 15 kms in length was selected for schools situated in the suburbs of New Market. This route is selected as the bus drives takes the bus through relatively higher air polluted area due to traffic input towards CBD. The starting point selected for the route is situated in Glendowie Opposite 411 Tamaki Drive (stop 7344) and ends at Owens Rd by Epsom Girls Grammar Gate (stop 1495). The duration of the bus ride is about 45 minutes to 1 hour. As seen, there are many stops on this route to get to various schools but we measure the dose concentration from longest route, that is from the starting to the end point.

Table 1: Bus Details






NZ Bus


Baradene College, Dilworth School, Diocesan School for Girls, Epsom Girls Grammar, Kings College, Kings School, Remuera Intermediate, Remuera Primary, Saint Kentigern Boys School, Saint Kentigern Girls School, Selwyn College, St Cuthbert’s College


Opposite 411 Tamaki Drive (stop 7344), Tamaki Drive, Vale Road, Bay Road, Riddell Road, Rochdale Avenue, Chesterfield Avenue, Maskell Street, St Heliers Bay Road, Kohimarama Road, Kepa Road, Purewa Bridge, Orakei Road, Remuera Road, Market Road, Campbell Crescent, Manukau Road, Clyde Street, Margot Street, Mount St John Avenue, Manukau Road, Alpers Avenue, Gillies Avenue, Owens Road, Owens Rd by Epsom Girls Grammar Gate (stop 1495).


Last updated 11 July 2018

Source: Auckland Transport, school bus routes. (https://at.govt.nz/bus-train-ferry/timetables/school-timetables/kings-school/)



Fig 2: School bus route from Glendowie to Epsom schools as seen from Google maps


Traffic data is obtained from Auckland council website and the same can be utilized to understand the traffic flow rate during the commute of the school bus considering the morning and evening peak hour periods.

Data collection and instrumentation

The exposure to & accumulation of pollutants like Ultrafine particles (UFP) which is emitted from diesel engines and Carbon Monoxide (CO) which is emitted from petrol engines is measured. The selection of these pollutants is also due to the availability and mobility of the monitoring equipment which is used for studies on personal exposure. The instruments used will be P-Track ultrafine particle monitor (TSI instrument) and a Langan portable carbon monoxide monitor (Langans Products, Inc) which are used in previous studies  (Kaur et al., 2005b; Chan et al., 1999; Flachsbart, 1999; Lui et al., 1994; Wong et al., 2011; Vellopoulou et al., 1998; De Bruin et al., 2004). A participant will help in volunteering as an additional help in carrying out the data collection which will take place inside the bus to and from the starting to the ending point of the commute. Air pollution data will be collected in 10 sec interval of the journey inside the bus. Sampling of data for morning commute will start from the departure of the bus, that is., 7.15 a.m. and end at arrival at around 8.15 a.m. at the end of the journey. The evening commute will start at 3.15 p.m. and end at around 4.15 p.m. depending upon traffic. The data collection will be carried out for around 15 days. The time of the journey will be recorded. 

Pollutant concentration inside a non-school bus will also be collected for comparative studies. The time at the start and end of the journey will be noted along with the time interval. Route and time of the non-school bus will remain the same as the school bus route for better results. Meteorological parameters like temperature, humidity, wind speed & wind direction will be monitored during the travelling time throughout length of the journey.

Bus Characteristics

Data about operating school buses will be collected from Auckland Transport. Bus details like mileage, age, fuel used, type of engine will be complied (Adar & S’Souza 2015). A reference of non-school bus will be selected which resemble the similar characteristics for more accurate results. Pollutant concentration of UFP and carbon monoxide will be measured inside the school bus which travels in a polluted/traffic area and outside the bus at each stop, preferably in the front, where the diesel exhaust of the bus is far off, for obtaining comparative results. This will give the difference between self- pollution accumulated in the bus and the pollution on road (Adar & D’Souza, 2015). Adjacently, the pollutant concentration in a non-school bus will also be monitored. This is to differentiate the accumulation of pollution concentration between a school bus and a non-school bus. Data on ambient air quality obtained from air pollution monitoring sites nearby the school is used for the study.

Data analysis

Carbon monoxide and ultrafine particle matter concentrations will be analysed using time series data analysis based on the exposure. This will be carried out for both selected school bus and non-school buses which travel the same route and at the same time. By using this data average commuter exposure of these pollutants is calculated. The average exposure pollutant concentration is calculated for both the school bus and non-school bus for the fixed time period of the research. This average exposure will be compared with the exposures measured at early morning and evening commute for each of the pollutant measured using statistical analysis (unpaired T tests). The ambient air quality will also be considered at the same time interval during the commute of the school bus. The average of the same will be calculated and compared with that of the school bus concentration. Peak concentrations for both the pollutants will be determined in school bus, non-school bus and ambient air concentrations. Difference in the peak concentrations of both the commutes will be determined during the length of the experiment conducted.


The timeline for this study will be 15 days.

The estimated cost will be around NZD$ 2000

Sl No




Ethonol for P-track ultrafine particle monitor (TSI Instrument)



Bus fare is 3.75 per ride for 1 month (5 days a week)



Miscellaneous (Assistant, renting instrument etc)






Beatty & Shimshack, (2011). School buses, diesel emissions, and respiratory health, Journal of Health Economics, 30, 987-999.

Behrentz E, Sabin LD, Winer AM, Fitz DR, Pankratz DV, Colome SD, Fruin SA. Relative importance of school bus-related microenvironments to children’s pollutant exposure. J Air Waste Manag Assoc 2005; 55:1418–1430.

Wu CF, Delfino RJ, Floro JN, Quintana PJE, Samimi BS, Kleinman MT, Allen RW, Liu LJS. Exposure assessment and modeling of particulate matter for asthmatic children using personal nephelometers. Atmos Environ 2005;39:3457–3469.

Sabin LD, Kozawa K, Behrentz E, Winer AM, Fitz DR, Pankratz DV,Colome SD, Fruin SA. Analysis of real-time variables affectingchildren’s exposure to diesel-related pollutants during school buscommutes in Los Angeles. Atmos Environ 2005;39:5243–5254.

 Rea AW, Zufall MJ, Williams RW, Sheldon L, Howard-Reed C.The influence of human activity patterns on personal PMexposure: a comparative analysis of filter-based and continuousparticle measurements. J Air Waste Manag Assoc 2001;51:1271–1279.

Dockery, D.; Speizer, F.; Stramn, D.; Ware, J.; Spengler, J.; Ferris, B. G. Effects of inhalable particles on respiratory health of children. Am. Rev. Respir. Dis. 1989, 139, 587-594.

Lipsett, M. The Hazards of Air Pollution to Children. In Environmental Medicine; Brooks, S. M., Gochfeld, M., Herzstein, J., Schenker, M., Eds.; Mosby: St. Louis, MO, 1995.

Thurston, G. D. Particulate Matter and Sulfate: Evaluation of Current California Air Quality Standards with Respect to Protection of Children; New York School of Medicine, 2000; available from http://www.arb.ca.gov/ch/ceh/001207/pmsul.PDF (accessed Feb 17, 2005).

Public Hearing to Consider Amendments to the Ambient Air Quality Standards for Particulate Matter and Sulfates; California Air Resources Board: Sacramento, CA, 2002; available from http://www.arb.ca.gov/research/aags/std-rs/pm-final/pm-final.htm.

 Wallace, L. A. Personal exposure to 25 volatile organic compounds: EPA’s 1987 TEAM study in Los-Angeles, California. Toxicol. Indus. Health 1991, 7, 203-208.

Flachsbart, P. G. Long-term trends in United States highway emissions, ambient concentrations, and in-vehicle exposure to carbon monoxide in traffic. J. Expos. Anal. Environ. Epidem. 1995, 5, 473-495.

Wallace, L. A. Environmental exposure to benzene: an update. Environ. Health Perspect. 1996, 104, 1129-1136.

Rodes, C.; Sheldon, L.; Whitaker, D.; Clayton, A.; Fitzgerald, K.; Flanagan, J.; DiGenova, F.; Hering, S.; Frazier, C. Measuring Concentrations of Selected Air Pollutants inside California Vehicles; Research Triangle Institute: Research Triangle Park,NC, 1998; available from http://www.arb.ca.gov/research/abstracts/95-339.htm.

Gulliver, J.; Briggs, D. J. Personal exposure to particulate airpollution in transport microenvironments. Atmos. Environ.2004, 38, 1-8.

Shikiya, D.C., et al, 1989. In-vehicle air toxics characterization study in the South Coast Air Basin. Final Report, South Coast Air Quality Management District.

Chan, C.C., et al., 1991. Driver exposure to volatile organic compounds, CO, ozone, and NO2 under different driving conditions. Environmental Science and Technology 25, 964–972.

Lawryk, N.J., et al., 1996. Concentrations of volatile organic compounds in the passenger compartments of automobiles. Environmental Science and Technology 30 (2), 810–816.

Behrentz, E., et al., 2004. Measuring self-pollution in school buses using a tracer gas technique. Atmospheric Environment 83 (23), 3735–3746.

Adar, S., et al., 2008. Predicting airborne particle levels aboard Washington Stateschool buses. Atmospheric Environment 42 (33), 7590–7599.

Beatty &Shamshik (2011). School buses, diesel emissions, and respiratory health, Journal of Health Economics 30 (987– 999)

Wargo, J., et al., 2002. Children’s Exposure to Diesel Exhaust on School Buses. Environment and Human Health, Inc., North Haven.

Sabin, L.D., et al., 2005. Characterizing the range of children’s air pollutant exposure during school bus commutes. Journal of Exposure Analysis and EnvironmentalEpidemiology 15, 377–387.

Bennett, W.D., Zeman, K.L., 1998. Deposition of fine particles in children spontaneouslybreathing at rest. Inhalation Toxicology 10, 831e842

Dirks, K. N, Salmond, J. A and Talbot, J. A, 2018. Air Pollution Exposure in Walking School Bus Routes: A New Zealand Case Study, International Journal of Environmental Research & Public Health, 15, 2802, pp 1-12

Zhu, Y.F., Eiguren-Fernandez, A., Hinds, W.C., Miguel, A.H., 2007. In-cabin commuter exposure to ultrafine particles on Los Angeles freeways. Environmental Science & Technology 41, 2138-2145

Xu, Bin & Chen, Xiaokai & Xiong, Jianyin, 2016. Air quality inside motor vehicles’ cabins: A review. Indoor and Built Environment.


Dangers of Exposure to Everday Chlorine

 Have you ever been cleaning your bathroom and made a run for the window because the fumes were just too overwhelming? Have you ever tasted tap water with a funny after taste? How about red eyes and a rash on the body after a few laps in the pool to cool off? Many of us just brush aside these moments and do not think about the fact that we have been exposed to something which created a negative reaction in our bodies. Chlorine bleach has been used for years in the household for various applications and is generally regarded as safe, but if we take a closer look at this multipurpose chemical we may realize that we need to rethink our choices and take extra care in our selection and use.

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 Chlorine bleach is a chemical that is diluted for use in the household. It is a mixture of water and the chemical sodium hypochlorite (3 to 9 percent).1 Chlorine is also found in many other types of household cleaners including dishwashing detergents, mould and mildew removers, toilet bowl cleaners, disinfectants and chlorinated scouring powder.2 While no one can doubt the efficacy of these products it is undoubtable that frequent use exposes the user to toxic gas emissions which have been linked to significant health dangers.

 Chlorine is harmful to the lungs. Breathing in chlorine emissions can cause difficulty breathing, coughing and inflame the airways. It can cause nausea, vomiting, chest tightening and pain. Chlorine compounds are also highly corrosive and can cause damage and irritation to the eyes and skin and if severe exposure occurs long term illnesses and death have been reported.3 But can this really affect you? The simple answer is yes. In many instances misuse and the mixing of different household cleaners create chemical reactions which cause the emission of toxic chlorine and other gases. Within close proximity, you at are at risk of the inhalation of these toxins and the unfortunate effects with as many uses. This means multiple times per month!

 Swimming is a relaxing pastime enjoyed by almost everyone. It is an excellent form of physical activity with many health related benefits. Chlorinating agents are the most common type of chemical added to swimming pools as disinfecting agents to prevent the growth of unwanted organisms in the pool water. Chlorinating agents are also used in hot tubs, spas, wading pools and whirlpools.4 Research suggests that children who swim in chlorinated pools have a notably increased risk of developing allergies or asthma. The risk is directly related to the number of hours spent swimming in chlorinated pools.5 According to the U.S Environmental Protection Agency those who swim or use a hot tub frequently could have greater dermal and possibly inhalation exposures to chlorine.6 Additionally, Belgian researchers also found that the risks of hay fever and other allergies more than doubled with significant exposure to chlorinated pools.7

 Chlorine is present in drinking water in minimal amounts which is considered safe, but ingesting chlorine in its other forms such as bleach or household chemicals or pool water and inhaling chlorine gas emissions can cause chlorine poisoning which is considered a medical emergency.8 If this occurs, one must contact emergency services and go to the hospital immediately.

 So what can we do to reduce our chlorine exposure and these negative effects? Firstly, we can limit the purchase of chlorine based household products, choosing instead natural or organic products. If we must choose chlorine based products then we must ensure responsible use and take actions to protect ourselves such as wearing gloves, keeping the area well ventilated, refrain from mixing household cleaners particularly those with ammonia and chlorine, reading and following the instructions for use and storing chemicals in a safe place away from the reach of children to prevent accidental poisoning.

 Similarly, we can opt for swimming in pools which are disinfected by alternative agents such as silver copper ion generators or salt water. If this is not possible be sure to try not to ingest pool water, wear goggles and skin barrier creams and to rinse off immediately after swimming to minimize the risk of excessive chlorine exposure. There have not been any epidemiological studies that have specifically examined free chlorine concentrations in water and long-term health effects in the human population 9 so if you are concerned about ingesting chlorinated tap water then distilled, spring or other types as water are available as well as water purification systems which can be set up in the home.

 Chlorine compounds are all around us in various applications. Being aware of this and the potential dangers which these substances pose can help us to ensure responsible use and therefore protect ourselves and families from the harmful effects. 


Canadian Centre for Occupational Health and Safety 2019. OSH Answers Fact Sheet. Working with Chlorine Bleach (last updated 2017 Feb 14). Accessed 2019 Sept 19 https://www.ccohs.ca/oshanswers/chemicals/bleach.html

Bell-West Sarah C. 2015. Cleaning up confusion about bleach. Chemistry, efficacy and practical applications in health care settings-Clorox Healthcare. Accessed 2019 Sept 19 https://ipac-canada.org/photos/custom/OldSite/webinars_open/2015%20webinar%20-%20Chlorox%20-%20confusion%20about%20bleach.pdf

U.S National Library of Medicine 2019. Tox Town – Chlorine (published 2017 May 31) Accessed 2019 Sept 19. https://toxtown.nlm.nih.gov/chemicals-and-contaminants/chlorine

Canadian Centre for Occupational Health and Safety 2019. OSH Answers Fact Sheet. Swimming Pool Products (last updated 2018 Jan 08 14). Accessed 2019 Sept 19 https://www.ccohs.ca/oshanswers/chemicals/swimming.html

Andersson M et al. 2018. Early life swimming pool exposure and asthma onset in children – a case-control study Environmental Healthvolume 17, Article number: 34 (2018) Accessed 2019 Sept 19 https://ehjournal.biomedcentral.com/articles/10.1186/s12940-018-0383-0

U.S. Environmental Protection Agency. 1994a Managing ecological risks at EPA: issues and recommendations for progress. Washington, DC: Center for Environmental Research Information, U.S. Environmental Protection Agency. EPA/600/R-94/183. Accessed 2019 Sept 19 https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-chlorine-guideline-technical-document/page-3-guidelines-canadian-drinking-water-quality-chlorine-guideline-technical-document.html

Bernard A et. Al. 2009. Paediatrics Impact of chlorinated swimming pool attendance on the respiratory health of adolescents 124(4):1110-8. doi: 10.1542/peds.2009-0032. E pub 2009 Sep 14 Accessed 2019 Sept 19 https://www.ncbi.nlm.nih.gov/pubmed/19752078

 Canadian Centre for Occupational Health and Safety 2019. OSH Answers Fact Sheet. Working with Chlorine Bleach (last updated 2017 Feb 14). Accessed 2019 Sept 19 https://www.ccohs.ca/oshanswers/chemicals/bleach.html

Canadian Centre for Occupational Health and Safety. 2004c. CHEM INFO Chemical Profile: Sodium hypochlorite solutions. Canadian Centre for Occupational Health and Safety, Hamilton, Ontario. Accessed 2019 Sept 19.


Effect of Simultaneous Exposure to Corrosion and Fatigue on Bond Strength Between CFRP and Steel Plates




Corrosion is a serious problem in civil infrastructures, which can significantly jeopardize the structural integrity of the element.  Damaged caused by corrosion can dramatically be exaggerated when combined with an existence mechanical loading (1).

Last few decades many studies carried out on repairing and retrofitting civil infrastructures using the advanced composite materials (1) (2) (3) (4) (5) (6). It has been shown that fiber-reinforced polymer (FRP) composite materials has had a dramatic impact on civil engineering techniques. Adhesively-bonded composites material has led to improve both structural integrity and sustainability performance of these structures. Thorough theoretical and practical studies have been adopted on CFRP to repair steel structures [4, 7, 10, 11, 13, 14, 19, 20-29]. Bond durability has been a focal concerned issue for many researcher [4, 7, 10. 11] due to its effect on the resultant panel. However, studies in this area performed so far have been limited and many issues lack clarification. For example, most studies have studied the behaviour of the bond durability when it has been affecting by either the environment or the loading, however, in most cases that these two factors are existing together in the same time.

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As such, and due to the lack of knowledge in studying the effect of the simultaneous effect of corrosion and fatigue on the steel repaired with CFRP. This chapter presents an experimental study into the combined effect of both a severe environment and mechanical loading (static or fatigue) on the steel repaired with CFRP. The attacking of a severe environment represented by 3.5 % NaCl stimulated sea water at 60 0C, which next will generate the required corrosion. However, these circumstances have to be accompanied with the mechanical loading (static or fatigue). As this is important since steel structures are widely used in conditions where the effect of both environment and mechanical loading are existing. In order to meet these requirements, an experimental design has been accomplished, a description of the experimental set-up and the methodologies that were developed to determine the simultaneous effect of corrosion and fatigue on CFRP/steel repairs is given in Section 5.2. Section 5.3 describes an experiment test that was performed to determine the diffusivity rate of normal modulus CFRP laminates. An experimental investigation into the bond durability of CFRP repairs to steel plates under the combined exposure of corrosion and fatigue is presented in Section 5.4. Section 5.5 presents the results of an experimental investigation performed to evaluate the CFRP/steel bond quality prior to testing. Finally, Section 5.6 discusses new finding made in section 5.4 that aspects of the classical lap joint theory (that underpin the recommendations given in the PABST program and presented in the US Composite Materials Handbook CMH-17-3G [1, 2] are invalid.

5.2 Set Up and Experimental Design

The test design developed to investigate the combined effect of the environment and the mechanical loading on bonded CFRP steel joints is shown in Figure 1. This design lay out, which is given in [3], provides exposure to the corrosive environment while the specimen undergoes mechanical loading, see Figure 5.1(a). Some changes have accomplished to the design in [3] with respect to the specimen size and the steel mechanical properties. This set up briefly consists of two corrosion chambers that are firmly connected with the machine and hold the specimen inside. The main chamber, which was made of acrylic, performs two crucial jobs. One is holding the solution prepared for this test program which is 3.5 % NaCl artificial sea water at a maximum temperature of 60 0C. This chamber also contains a metal grip which penetrates through its bottom and connects the specimen to the lower grip of the fatigue machine. This chamber was not covered at the top as this allows the specimen to be directly connected to the upper grip of the machine. It also has two apertures, upper and lower apertures used for solution inlet and outlet respectively.

Circulation of the inner solution which is inside the chamber was continuously needed to maintain the temperature as same as the solution in the water path as indicated in Figure 5.1(d), to this end a heater and a pump were used to circulate the water and control its temperature inside the chamber. An additional chamber, which was made of metal, embraced the main chamber. The role of this “second” chamber, which is labelled number 7 in Figure 5.1(b), was to guarantee no solution leakage and to support the whole rig inside the upper and lower machine grips.


Figure 5.1: Experimental design for the simultaneous effect of environment and     load: a) A schematic view of the design set-up [3], b) experimental set-up of the durability test c) a view of the secondary chamber of the rig, and d) the water bath which contains water pump and heater.

In order to enable fatigue testing to be performed in a normal way, while the specimen is immersed totally in the environment, an additional grip was used to handle the specimen from one end and to connect it to the fatigue machine from the other. The grip that was submerged completely in the environment was made of stainless steel so as to resist the anticipated corrosion, see Figure 5.1(c). The test specimens were designed to fit inside the rig and as such were designed to be a maximum of 400 cm long. The specimens also had a hole at one end in order to be gripped inside the chamber. Thus the bearing capacity of this member was a critical design consideration.

5.3The Moisture Uptake Investigation for Normal Modulus CFRP Plates (Diffusivity Rate)

Prior to onset of the bond durability experiment program, a crucial consideration should be taken into account. The double lab joints specimen configuration has two outer surfaces of CFRP, see Figure 5.2. Hence when this specimen is exposed to the environment (the moisture) during testing, it is important to establish if the moisture has reached the interface between the composite and the adhesive [4].  Consequently, the time required for the moisture to reach the interfaces in-between the composites/adhesive and the adhesive/steel will be determined in this section. To this end, a diffusivity rate experiment of CFRP materials was performed in order to (approximately) estimate the time required for the moisture to be absorbed by the composite and reach the composites/adhesive interface.



                  Figure 2: Configuration of double lab joint specimen (not to scale)

This was determined as per the standard test, as detailed in ASTM D5229. To this end, 10 CFRP plates specimens of the dimensions (50 x 200 x 1.2 mm) were prepared as shown in Figure 5.3. The dimensions were chosen to be the same as CFRP plates in Section 5.2.



Figure 5.3: Normal modulus CFRP plates

Two different exposure temperatures, viz, 20 and 50 0C, were utilised. The weight measurements were done at various time intervals every 24 hour for the first week and every 2 days for the next 12 days. This was done by removing the specimen from the water tank, and extra water on the surface was dried using clean tissues. The change in weight as a percentage was plotted against the square root of time (√t), where t is the time in days. By assuming that the diffusion occurs in one dimension, and ignoring the thickness effect, such as the case represented by a thin film of a thickness adsorbing a fluid according to Fick’s law with constant surface boundary conditions, the amount of diffusant, M2, taken up by the sheet in a time, t, is given by [5, 23], Once the moisture uptake become constant then this is the time that the sea water requires to penetrate the CFRP plate and reach the interface in between the composite and the adhesive, see Figure 5.5. Accordingly, by using equation (1), the diffusivity rate of normal modulus CFRP material has been calculated.

D=π+h4M2+M2–M1t2–t12+1+hl+hw–2  ______________________        (1)

Here h, l, and w are thickness, length, and width of the panel, M1 and M2 are the equilibrium sorption attained theoretically at time t1 and t2, respectively. It was found that the times required for normal modulus CFRP laminate immersed in 50 0C and 20 0C to reach their maximum moisture weight gains were approximately 10 to 13 days and 15 to 17 days respectively. This is shown in Figure 5.5, which shows the theoretical moisture uptake behaviour predicted using Fick’s second law of diffusion [6, 7]. Subsequently, the coefficients of diffusivity were 2.52 x10-9 and 3.00 x 10-9 for 20, 50 0C respectively see Table 5.1.

These specimens were first dried in an oven for 24 hours and weighed using a digital balance with precision to 0.01g as shown in Figure 5.4 (a) and (b) respectively. They were then immersed in the environment which was 3.5% NaCl simulated sea water see Figure 5.4 (c) and (d).

Figure 5.4 Steps indicating moisture uptake test, a) Drying step in an oven, b) specimen weighing, c) specimen in sea water, d) specimen in the environment (20 and 50 0C 3.5% NaCl)
























Figure 5.5 Moisture uptake curve for the CFRP laminates immersed in sea-water

Table 5.1: Characteristics of moisture uptake and the diffusivity coefficient of normal modulus CFRP laminate at 20 and 500C 3.5%wt NaCl .

The Environment



  Maximum moisture

          Uptake (%)

Coefficient of Diffusion      (mm2/s) x 10-9

3.5 %wt NaCl




3.5 %wt NaCl












5.4 The Bond Durability Experiment

5.4.1 Test Configuration and Material Properties

CFRP/steel double overlap fatigue specimens (dofs) with dimensions shown in Figure 5.6 were fabricated. These specimens consisted of two 350 grade mild steel inner adherends bonded to normal modulus (E = 200 GPa) CFRP outer adherends. The dimensions of the steel inner adherents were: 180 mm long, 50 mm width and 5 smm thick. The size and configuration of specimens were designed according to AS1391 specifications (2001) and designed to fit in the designed rig and be tested under fatigue load.

The two outer adherends were a layer of CFRP composite, MBRACE laminate normal modulus (E = 210,000 MPa), 200mm long, 50 mm wide and 1.4 thick see Figure 5.7(b). A CFRP laminate was used since it is perhaps the most commonly used composite material used in the repair of steel infrastructure.


Figure 5.6 Schematic design of the CFRP/steel double lap joint.





                     Figure 5.7: Material photos (a) Mixed structural adhesive (b) CFRP laminate.

The adhesive used in this test was the epoxy resin adhesive (Araldite 420 A/B) see Figure 5.6(a). Araldite 420 has widespread applications in bonding various structural substances such as metal, wood, rubber, composites and many plastics. This is attributed to its typical properties, namely, design flexibility, extremely tough but resilient, relative rigidity, and its cost-effective characteristic, in addition to it’s room temperature curing property [4] The manufacturer outlines that the CFRP laminate has a tensile strength and an elastic modulus of 3,300 MPa and 210 GPa respectively. A Poisson’s ratio ν12 of the laminate was assumed to be 0.35, which is a typical value for this type of adhesive [8, 11].

5.4.2 Specimens Preparation

The dofs specimen geometry was originally proposed in [9] since it closely simulates the stress state in both the repair and the adhesive associated with a composite repair to a cracked metal structure.

As recommended in [10] surface sandblasting was used as a mechanical surface preparation technique to roughen steel surface. Surface roughness helps to increase the surface area, which enhances adsorption and interlocking, thereby facilitating adhesion and bonding. The steel surface was abrasively sandblasted by subjecting it to an accelerating media (16-grit sand) through a blasting nozzle by means of compressed air. (Note that the gun should be held away about 5 cm from the surface at 450 angles). The (roughened) steel surface was then cleaned first by compressed air to remove the dust sand particles and secondly with acetone using a clean brush. Roughening the surface (sandblasting) and then wiping it with chemical solvent (acetone) can produce a contamination free surface, chemically active and fresh surface, and an interface resistant to hydration due to solvent [4,7,8,11]

A layer of Araldite A/B adhesive was applied to the steel. The patches were subsequently applied, and the surfaces were then rolled using a plastic roller to remove the air bubbles and the extra adhesive. This was done to obtain an even and thin layer of epoxy which comes of two parts A & B, as they should be mixed before using, according to the recommended percentage of 10-4 respectively. The specimen was subsequently left for curing at room temperature for at least 15 days.

5.4.3 Specimens Exposed Process

1. Control Specimens

After curing, 18 specimens were used to determine the ultimate strength of the bond. These specimens were static tested at three temperatures (20, 40, 50 0C) and were taken as control specimens. Nine of these specimens were immersed in sea water at the three temperatures (20, 40, 50 0C) for two weeks prior to tensile testing. This was done with regard to the moisture uptake equilibrium of normal modulus CFRP laminate as calculated in Section 5.3. The remaining nine specimens were tested without pre-immersion.

All specimens were strained, in a 3.5 % (by weight) NaCl solution (i.e., artificial seawater), at a rate of 2 mm/min. To allow for the possible scatter, three (control) specimens were tested at each of the three exposure temperature.

Two dummy specimens with 4 attached thermocouples were used to control the temperature inside the chamber, see Figure 5.8. Before starting the test, specimens were soaked at the required temperature for 25-30 min, to ensure that the entire specimen attained the required temperature. The specimen is then placed in the chamber and submerged in the environment, and then loaded at a rate of 2 mm/min.




Figure 5.8:  Dummy specimens with attached thermocouples determine the temperature of the specimens inside the chamber


2. Fatigued Specimens

An additional set of 18 specimens was fatigue loaded under constant cycles, up to a maximum load of 20 % of the specimen’s ultimate strength which (that was independently determined). Nine of these specimens had been pre-exposed at the three different temperatures (20, 40, 50 0C), while the other nine were directly tested under fatigue load (i.e., without pre-exposure). Under each condition, triplicate tests were performed, in order to estimate the scatter in the data. Fatigue testing was performed using an MTS Instron machine with load cell capacity of 100 kN. All tests were performed at a frequency of 10 Hz and a stress ratio of 0.1. The tests were terminated after 2 million cycles and the specimens then subjected to static load until failure. This was done in order to determine the effect of fatigue load on the ultimate strength of the bond. The results of these tests are shown in Table 2.

5.4.4 Results and Discussion

The average ultimate tensile strengths for the specimens and the coefficients of variation with and without pre-exposure to the environment for two weeks are shown in Table 5.2. Here we see that the failure load decreased as temperature increased. On the other hand, pre-exposure procedure has no significant effect on the failure load see Figure 5.9. Figure 5.10 shows that the specimens exhibited both cohesive and adhesive failure at all temperatures [7, 11, 22]. Unfortunately, this means that the surface preparation was inappropriate. This study led to the realisation that alternative surface preparations were needed.

Table 5.2 Average ultimate loads (Fult) and coefficient of variation of CFRP laminate repaired steel plates at different temperatures with and without pre-exposure to environment

Temperature (oC)

Average value of Ultimate loads Fult (kN)

Coefficient of variation

Ultimate strength (kN) (Fave) without pre-exposure










Ultimate strength (kN) after immersion for 2 weeks (Fave)



















               Figure 5.9 Static strength of CFRP laminate/steel bonded specimens

Figure 10 Optical images of control specimens after failure, a) with pre-exposure b) without pre-exposure to environment

Bai (2013) [10] reported the effect of varying temperature on tensile strength, whereas, Borrie (2015) [11] tested samples after pre-exposure to environment at different temperatures. In the present study, tests were conducted under the simultaneous effect of environment, load, and with and without pre-exposure. The dimensions and the materials were chosen to be the same as those in [10, 11] for the purpose of comparing the results. Among the various test conditions, simultaneous exposure of pre-exposure samples to environment at an elevate temperature conditions the most severe condition that deteriorates the ultimate strength most drastically. The three various studies is presented in Figure 5.11. The raw data for all specimens can be found in Table A1(in appendix A).

Figure 5.11 The bond ultimate strength FULT(kN) of CFRP repaired steel obtained under four different procedures of exposure to the environment.

Figure 5.10 reveals that the failure modes involved both cohesive and adhesive failure, which is similar to the failure of the specimens tested under the combined effect of environment and fatigue load see Figure 5.12. This suggests that the bonding process recommended in [7, 11, 19, and 20] is not optimal. Thus, a conclusion will be examined in more details in Chapter 6.



400C 0jjhk0CC00C


500C 0jjhk0CC00C

500C 0jjhk0CC00C



Figure 5.12 Optical images of fatigued specimens after failure, a) with pre-exposure b) without pre-exposure to environment

5.5 A Mean for Evaluating Bond Quality Prior to Testing

The results described in the previous section revealed that means for quantifying the bond prior to testing is essential. This has been a shortcoming in several previous studies [21]. Unfortunately, “kissing bonds” and poor bond can’t be determined via standard NDI tests. To meet this challenge, Lockin-thermography, which uses Kelvin’s law to link the infra-red emission to the surface stress field, this has been widely used to study composite repairs and fatigue life extension process [15].

In this context, researchers have shown that corrosion can be detected using Lock-in infrared thermography in steel and galvanized steel panels that were coated with an organic paint. Aerospace researches have been also shown that material disbond can be easily detected using this system. Lock-in thermography involves heating the structure using a sinusoidal input of heat energy at a frequency ω, produces both amplitude and phase difference images both at the (1st harmonic) ω and also other harmonics the most relevant of which (to this study) is the 2nd harmonic 2ω. The amplitude image represents the amplitude (peak-to-peak) thermal response of the structure. The phase image is generated by phase difference measured between the input and the measured signal. The phase image is often more useful than the amplitude image for detecting subsurface defects.

In this part, Lock-in infrared thermography has been used to monitor the disbanding in the interface between CFRP and steel in DOF specimen.

To evaluate the potential of this procedure, the CFRP repairs to steel specimen was fatigue cycled, (see Figure 5.13). Figure 5.14 shows the resultant stress field. Here the dislocation in the stress field at the edges located over the joint are indicated. Such disbonds will induce adhesive failure in an aggressive environment. This test substantiates the conclusion reached in the previous experiment that the process used to bond the specimens need to be improved.







Figure 5.13: Photograph of the dofs under test


                                      Side A                                                                  Side B

                   Figure 5.14 Stresses on the surface of the patch of two sides (upper adherend)


5.6 Designing CFRP repairs, the classical lap joint theory testing

The CMH-17-3G Composites Material Handbook [1] documents the formulae used to design bonded joints. These formulae which were validated as part of the USAF Primary Adhesively Bonded Structure (PABST) program [2], were originally developed by Dr. John Hart-Smith [3, 4]. In This formulation, it is assumed that the stresses are constant through the inner (steel) and outer (CFRP) adherends. It predicts that for a dof specimen the peak stress in the adherend occurs directly over the joint. Figure 15 reveals, that part of the PABST (Hart-Smith [15-17]) analysis is incorrect since the peak stresses actually occur slightly to each side of the joint. This feature is due to the complex 3D nature of the stress field in the dof specimen [24].

Figure 5.15 Stresses along line AB in the centre of the patch (shown in Figure 14)

The next stage in this study was analysing the stresses along the joint of dof specimen using the finite element model (FEMAP & NASTRAN software) see Figures 5.16 and 5.17.

Figure 5.16 The configuration of the half of the dof specimen using FEMAP and Nastran software

Figure 5.17 The analysing the DOFS using FEMAP and Nastran software

                 Figure 5.18: Stress at Top Surface, half of the specimen

 It is clear from the predicted stresses along the surface of the joint which resulted from using the finite element model (see figure 18), that the stress distribution have a camel hump configuration, which means that the peak of the stresses lies on either sides of the joint and not over the joint directly. This means that the FEMAP models clearly simulated the stress configuration and the results were in satisfactory agreement with the experimental results.

 5.7 Conclusions

From the investigations reported in this chapter, following conclusions can be drawn:

1)   The CFRP bonded steel specimens tested in an aggressive environment showed a significant reduction in their bond strength;

2)   By comparing the results with those presented by Borrie [11] and shown in Fig.5.11, it is clear that pre-exposure followed by an aggressive environment significantly reduces the residual strength of the bond;

3)   The failure modes involved a combination of cohesive and adhesive failure;

4)   Inspection of the bond quality reveals the presence of disbond as the adhesive touching but not bonding). Therefore, an alternative bonding process is required to get better bonding;

5)   It is clear that effective bonding process that can withstand combined fatigue-environment is required. Chapter six will examine the Boeing-USAF surface preparation procedures viz: the use of grit blast and sol gel;

6)   It has been proved experimentally and analytically that the peak of the stress in the double overlap fatigue specimen (dof specimen) lies on either sides of the joint and not exactly over the joint, and this finding is important since it contradicts the PABST formula which stated that the peak lies directly over the joint.

5.8 References

CMH-17-3G, Composite Materials Handbook, Volume 3:  Polymer Matrix Composites Materials Useage, Design and Analysis, Published by SAE International, March 2012.

Potter DL., Primary adhesively bonde d structure technology (PABST): Design handbook for adhesive bonding, USAF Technical Report, AFFDL-TR-79-3129, November 1979.

Jafari S., Singh R., Corrosion fatigue behaviour of a common AZ91D magnesium alloy in modified simulated body fluid, Advanced Materials Research, (2014), Volume 891, Issue 5, pages 267-272.

Liu, H.,Zhao XL., and Al-Mahaidi R., Effect of fatigue loading on bond strength between CFRP sheets and steel plates. International Journal of Structural Stability and Dynamics, 2010. 10(01): p. 1-20.

J. Crank and G.S. Park, Diffusion in polymers, Book, London; New York, N.Y., Academic Press, 1968.

Al-Harthi M, Loughlin K, Kahraman R. Moisture diffusion into epoxy adhesive: testing and modeling. Adsorption 2007;13: 115–20.

     Nguyen T, Bai Y., Zhao XL., and Al-Mahaidi R., Durability of steel/CFRP double strap joints exposed to sea water, cyclic temperature and humidity. Composite Structures, 2012b. 94(5): p. 1834-1845.

Baker A. and Jones R., Bonded Repair of Aircraft Structure. 1988, The Hague: Martinus Nijhoff Publishers. pp 107- 173.

Baker A. A. (2002) Introduction and overview. In: Advances in the Bonded Composite Repair of Metallic Aircraft Structure. Elsevier, p. 1-18.

                    Bai Y Nguyen TC, Zhao X-L, Al-Mahaidi R. Environment-assisted degradation of the bond between steel and carbon-fiber-reinforced polymer. J Mater Civ 2014; 26(9):1–8.

                    Borrie D, Liu H., Zhao XL., Singh R, Bai Y., Bond durability of fatigued CFRP-steel double-lap joints pre-exposed to marine environment. Composite Structures, 2015. 131: p. 799-809.

                    Matta F. (2003) Bond between steel and CFRP laminates for rehabilitation of metallic bridges, Ph.D Thesis, University of Padua, Padua.

           Zhao, X.-L., et al., Effect of dynamic loading and environmental conditions on the bond between CFRP and steel: state-of-the-art review. Journal of Composites for Construction, 2013. 18(3).

                     Fawzia, S. and M.H. Kabir. A review on environmental durability of CFRP strengthened system. In Australasian Structural Engineering Conference 2012: The past, present and future of Structural Engineering. 2012. Engineers Australia.

                    Hart-Smith, L.J., Adhesively bonded double lap joints, NASA CR 112235, January 1973.

                    Thrall EW., Primary adhesively bonded structure technology (PABST): Design handbook for adhesive bonding, USAF Technical Report, AFFDL-TR-79-3119, 1979.

                    L. J. Hart-Smith, “Further Developments in the Design and Analysis of Adhesive-Bonded Structural Joints”, Douglas Aircraft Company Paper 6992,

                    presented to ASTM Symposium on Joining of Composite Materials, Minneapolis, Minnesota, April 1980; published in ASTM STP 749.

                    M. Tavakkolizadeh and H. Saadatmanesh, “Fatigue strength of steel girders strengthened with carbon fiber reinforced polymer patch,” Journal of Structural Engineering, vol. 129, no. 2, pp. 186–196, 2003.

                    J. Teng, D. Fernando, T. Yu, and X. Zhao, “Treatment of steel surfaces for effective adhesive bonding,” in Advances in FRP Composites in Civil Engineering, pp. 865–868, 2011.

                    D. Schnerch, M. Dawood, S. Rizkalla, E. Sumner, and K. Stanford, “Bond behavior of CFRP strengthened steel structures,” Advances in Structural Engineering, vol. 9, no. 6, pp. 805–817, 2006.

                    Ahmed Al-Shawaf, Xiao-Ling Zhao, Adhesive rheology impact on wet lay-up CFRP/steel joints’ behaviour under infrastructural subzero exposures, Composites: Part B 47 (2013) 207–219.

                    X. HAN1,2, A. D. CROCOMBE1 , S. N. R. ANWAR1,3, P. HU2 , and W. D. LI2, “The Effect of a Hot–Wet Environment on Adhesively Bonded Joints Under a Sustained Load”, The Journal of Adhesion, 90:420–436, 2014.

                    Jones, R. and Paul, J., Aeronautical Research Laboratories, Australia, Structures Report 402 (1984).

                    Miller T. C., Chajes M. J., Mertz D. R. and Hastings J. N. (2001) Strengthening of a Steel Bridge Girder Using CFRP Plates. Journal of Bridge Engineering, ASCE, 6(6):514-522. (1)

                    Hollaway L. C. and Cadei J. (2002) Progress in the technique of upgrading metallic structures with advanced polymer composites. Progress in Structural Engineering and Materials, 4(2):131-148.

                    Liu H. B., Xiao Z. G., Zhao X. L. and Al-mahaidi R. (2008) Prediction of fatigue life for CFRP strengthened steel plates. Thin-walled Structures (Accepted for Publication).

                              Liu H. B., Zhao X. L. and Al-Mahaidi R. (2005a) The effect of fatigue loading on bonding strength of CFRP bonded steel plate joints. In: Proceedings of the International Symposium on Bond Behaviour of FRP in Structures, Hong Kong, China, p. 459-464.

                  Karbhari V. M., Chin J. W., Hunston D., Benmokrane B., Juska T., Morgan R., Lesko J. J., Sorathia U. and Reynaud D. (2003) Durability gap analysis for fibre-reinforced polymer composites in civil infrastructure. Journal of Composites for Construction, ASCE, 7(3):238-247.

Static Tensile Test of CFRP Laminate Repairs Steel



Ultimate Strength

F1ult (kN)

Ultimate Strength

After fatigue F2ult (kN)

Ultimate Strength        (kN)


Ultimate Strength        (kN)

(F2ave) after fatigue

Stress Ratio

(F2ave /F1ave)


Spe 2

 Spe 3


Spe 2

Spe 3

Direct Test under The Simultaneous Effect of Environment + Load































Immersed the Specimens for 2 Weeks Before the Test
































Exposure to Computer Disciplines

Q1 Give an Example of micro operations, microinstruction, micro program, micro code.
And. Example of micro operations: Shif, load, increment, add subtract, multiply and divide etc.
Example of micro programmes: chipsets.
Q2 How Information Technology can be used for strategic advantages in business?
Ans. It is defined as the study, design. development, implementation, support or management of computer based information systems particularly software applications and hardware applications. It can be used in the application in the business as it can be used to convert ,store,protect, process transmit and  security retrieve information.
Q3 What Characteristics of software make it different from other engineering products?
Ans.Software is a general term primarily used for digitally stored data such as computer programs and other kinds of information read and written by computers. Today, this includes data that has not traditionally been associated with computers, such as film, tapes and records. The term was coined in order to contrast to the old term hardware; in contrast to hardware, software is intangible, meaning it “cannot be touched”. Software is also sometimes used in a more narrow sense, meaning application software only. It is what we can call a set of programmes which are made in accordance while keeping in mind the needs of the customer. The difference between software and other engineering products is that the other engineering products such as machines and something else cannot be change its working or characteristics while made once but the software can be updated according to the needs of its user.
Q4What are different addressing modes available?
Ans. Types of Addressing Modes
Each instruction of a computer specifies an operation on certain data. The are various ways of specifying address of the data to be operated on. These different ways of specifying data are called the addressing modes. The most common addressing modes are:

Immediate addressing mode
Direct addressing mode
Indirect addressing mode
Register addressing mode
Register indirect addressing mode
Displacement addressing mode
Stack addressing mode

To specify the addressing mode of an instruction several methods are used. Most often used are :
a) Different operands will use different addressing modes.
b) One or more bits in the instruction format can be used as mode field. The value of the mode field determines which addressing mode is to be used.
The effective address will be either main memory address of a register.
Immediate Addressing:
This is the simplest form of addressing. Here, the operand is given in the instruction itself. This mode is used to define a constant or set initial values of variables. The advantage of this mode is that no memory reference other than instruction fetch is required to obtain operand. The disadvantage is that the size of the number is limited to the size of the address field, which most instruction sets is small compared to word length.
Direct Addressing:
In direct addressing mode, effective address of the operand is given in the address field of the instruction. It requires one memory reference to read the operand from the given location and provides only a limited address space. Length of the address field is usually less than the word length.
Ex : Move P, Ro, Add Q, Ro P and Q are the address of operand.
Indirect Addressing:
Indirect addressing mode, the address field of the instruction refers to the address of a word in memory, which in turn contains the full length address of the operand. The advantage of this mode is that for the word length of N, an address space of 2N can be addressed. He disadvantage is that instruction execution requires two memory reference to fetch the operand Multilevel or cascaded indirect addressing can also be used.
Register Addressing:
Register addressing mode is similar to direct addressing. The only difference is that the address field of the instruction refers to a register rather than a memory location 3 or 4 bits are used as address field to reference 8 to 16 generate purpose registers. The advantages of register addressing are Small address field is needed in the instruction.
Register Indirect Addressing:
This mode is similar to indirect addressing. The address field of the instruction refers to a register. The register contains the effective address of the operand. This mode uses one memory reference to obtain the operand. The address space is limited to the width of the registers available to store the effective address.
Displacement Addressing:
In displacement addressing mode there are 3 types of addressing mode. They are :
1) Relative addressing
2) Base register addressing
3) Indexing addressing.
This is a combination of direct addressing and register indirect addressing. The value contained in one address field. A is used directly and the other address refers to a register whose contents are added to A to produce the effective address.
Stack Addressing:
Stack is a linear array of locations referred to as last-in first out queue. The stack is a reserved block of location, appended or deleted only at the top of the stack. Stack pointer is a register which stores the address of top of stack location. This mode of addressing is also known as implicit addressing.
Q5 How will you differentiate b/w Arrays and Stacks? Explain by giving an example.
Ans.  An array is a systematic arrangement of objects, usually in rows and columns. Specifically, it may refer to several things.
Generally, a collection of data items that can be selected by indices computed at run-time, including:

Array data structure an arrangement of items at equally spaced addresses in computer memory

Array data type used in a programming language to specify a variable that can be indexed
A  stack is a last in, first out  abstract data type and data structure. A stack can have any abstract data type as an element, but is characterized by only two fundamental operations: push and pop. The push operation adds to the top of the list, hiding any items already on the stack, or initializing the stack if it is empty. The pop operation removes an item from the top of the list, and returns this value to the caller. A pop either reveals previously concealed items, or results in an empty list.

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A stack is restricted data structure, because only a small number of operations are performed on it. The nature of the pop and push operations also means that stack elements have a natural order. Elements are removed from the stack in the reverse order to the order of their addition: therefore, the lower elements are typically those that have been in the list the longest
Q6 How a translator is different from a Compiler?
Ans. A compiler is a computer program that transforms source code  written in a computer  language(the source language) into another computer language (the target language, often having a binary form known as object code). The most common reason for wanting to transform source code is to create an executable program.
The name “compiler” is primarily used for programs that translate source code from a high-level programming language to a lower level language (e.g., assembly language or machine code). A program that translates from a low level language to a higher level one is a decompiler
Q7 Out of Linear and Binary Search ,which one is preferred where and why?
Ans. Binary search is preffered over linear search because linear search is used for finding a particular value in a list that consists in checking every one of its elements, one at a time and in sequence, until the desired one is found
Its worst case cost is proportional to the number of elements in the list; and so is its expected   cost  if all list elements are equally likely to be searched for. Therefore, if the list has more than a few elements then binary search is preferred.
A binary search is an algorithm for locating the position of an element in a sorted listIt inspects the middle element of the sorted list: if equal to the sought value, then the position has been found; otherwise, the upper half or lower half is chosen for further searching based on whether the sought value is greater than or less than the middle element. The method reduces the number of elements needed to be checked by a factor of two each time, and finds the sought value if it exists in the list or if not determines “not present”, in logarithmic time. A binary search is a dichotomic divide and conquerr search algorithm.It is used for finding the telephone address for a given collection of name,address.

Controlling Exposure to Harmful Substances in the Workplace

Control of exposure to substances harmful to health by the UK government was first implemented during the late 19th century (Piney 2001). Today, Control of Substances Hazardous to Health (COSHH) assessments are used to address the risk associated with chemicals and how they may be used safely. This report considers three cleaning products which are used on a daily basis in the office environment in which I work: Freshline Bleach, Lifeguard 3 Way Toilet Cleaner and Mr Muscle Professional Kitchen Cleaner. COSHH assessments for these products are included in Appendix I.

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Chemicals used in office cleaning products and the processes involving these products
The three cleaning products assessed in this report contain a number of different chemicals. The components of each of these products are listed in Table 1, together with their toxicity, targets organs/organ systems and the recommended occupational exposure limits for these chemicals. The main targets organs for the chemicals in these products are the eyes and skin but the respiratory and digestive systems may also be affected if these products are inhaled or ingested.
Freshline Bleach is used for general cleaning and disinfecting purposes. In the office, it is used dilute for cleaning floors (e.g. corridors and toilet floors). A working solution is typically prepared in a mop bucket using tap water for dilution and the floors mopped. At the end of the procedure, the dilute solution is emptied down the drain and both mop bucket and mop rinsed in clean tap water. This bleach is also used neat for cleaning toilets and drains into which it is poured straight from the 5 litre container. Lifeguard 3 Way Toilet Cleaner is a cleaner, disinfectant and deodorizer that is used in the office to remove limescale and uric acid deposits on toilet bowls and urinals. The product is typically poured neat into the toilet bowl/urinal from the 1 litre container. Mr Muscle Professional Kitchen Cleaner is a cleaning spray used to clean all kitchen work surfaces, utensils and other equipment. This is sprayed neat onto surfaces and then wiped off using a disposable cloth.
Potential hazards for workers during handling of chemicals
The COSHH assessment included in Appendix I identifies the risk associated with the chemicals in each of the three cleaning products. There is the potential for all workers (both cleaning staff and office workers) to be exposed to these chemicals in the workplace. Cleaning staff are at the greatest risk of exposure at they will be handling the concentrated products. There is a risk of splashback from the bleach and toilet cleaner when pouring this into the toilet. There is also the potential for individuals to come into contact with undiluted chemicals during disposal of empty containers. Workers using bleach may inhale vapour if this is used in a poorly-ventilated area.
If cleaning cloths are used for multipurposes with a variety of different cleaning products without being properly rinsed between uses, there is also the potential for reactions to take place between chemicals in the different products which could be hazardous for workers. For example, if bleach comes into contact with acid, toxic gas may be liberated which could then be inhaled. There is also the potential for chemical reactions to take place if different cleaning products are used together, e.g. when cleaning toilets.
Monitoring workplace exposure and minimising the risk of exposure
The COSHH assessment identified Freshline Bleach and Lifeguard 3 Way Toilet Cleaner as medium hazards and Mr Muscle Professional Kitchen Cleaner as low hazard. For both the bleach and toilet cleaner in particular, it is essential that correct safety precautions are taken during the handling, use and disposal of these products.
Monitoring workplace exposure to the chemicals in these products is difficult and levels of exposure cannot be measured qualitatively. Regular inspections of the office kitchen and toilets will detect spillages that have not been cleaned up thoroughly which could mean workers are exposed to higher than normal levels of concentrated products. Keeping a record of the quantities of each product used (e.g. by asking staff to complete a log when they take a new container) would provide an indicator of the amounts being used within the office as a whole on a monthly/annual basis which may provide some indicator of occupational exposure levels. There is a designated health and safety officer within the office but regular inspections are not conducted and no formal training sessions are held to ensure that new staff joining the company are familiarised with correct office safety procedures.
A number of measures can be taken to minimise the risk of exposure. The COSHH assessments for all chemicals should be kept in a place where they can be found easily and all workers should familiarise themselves with these assessments and be aware of first aid measures and correct procedures for cleaning up spillages and disposal of solid waste. Training sessions for staff should be arranged if necessary. All workers using cleaning products must wear suitable personal protective equipment as detailed in the COSHH assessment (e.g. eye protection when working with concentrated toilet cleaner and eye protection, PVC/rubber gloves and protective overalls when working with concentrated bleach). Regular inspections would monitor whether correct working procedures are being followed and written reports from each inspection would provide a record over time.
In case of spillage of concentrated bleach or toilet cleaner on clothing, bags should be available to contain the soiled article(s) of clothing to send for cleaning and these should be clearly labelled with the hazard. PVC or rubber gloves should be replaced regularly and should be rinsed well with water if they have come into contact with concentrated solutions of bleach or toilet cleaner ensuring that no door handles or other surfaces are touched and contaminated with concentrated product. All spillages should be cleaned up thoroughly to minimise the risk of workers exposure to concentrated product and both spilt product and any solid waste associated with the spillage disposed of safely.
The risk of splashing is reduced by using spray containers (as in the case of Mr Muscle Professional Kitchen Cleaner), rather than the larger bottles or containers which hold the bleach and toilet cleaner, and less of the product is likely to be used with these types of containers. If concentrated bleach or toilet cleaner is spilt on toilet seats, it is important that this is cleaned up thoroughly to minimise the risk of skin contact. In all cases where concentrated bleach has been used in sinks, this should be rinsed thoroughly with copious amounts of water to reduce the risk of workers’ exposure and also to ensure safe disposal of the product. Previously, cleaning staff used to clean the office in the early evening when many staff were still working. This meant that neat bleach or toilet cleaner would be poured into toilet bowls or urinals and workers may then wish to use them, which significantly increased the likelihood of exposure to concentrated products. We have now requested that cleaning staff work later in the evening two nights per week when staff have already left and it is only on these occasions that the toilets are cleaned.
Cloths used for cleaning the kitchen should be rinsed thoroughly at the end of each use and not left where workers or even food could come into contact with concentrated products. Empty containers should be rinsed out well with water before disposal and the top of the container should be replaced to minimise the risk of individuals (i.e. office workers or waste disposal workers) coming into contact with undiluted chemicals. Products should be used in a well-ventilated area, particularly in the case of bleach. The office kitchen is poorly ventilated and has no windows that can be opened but the windows in the toilets can be opened before using products in these areas.
Correct storage of products will minimise the risk of workers’ exposure to chemicals. These products should ideally be stored in a locked storage area for which only suitable trained staff have access, and all products stored in original, closed containers, kept upright, in a cool place away from direct sunlight.
Plan of action for improvement
An audit showed that many staff were not aware of the risks from chemicals in cleaning products used in this office and that correct procedures for their safe use, disposal and storage were not being followed. Following this, a number of new measures have been, or will be, implemented. Training sessions have been arranged for all existing office staff to ensure they are familiar with COSHH assessments and safety procedures and these will be repeated when new staff join the company. Ensuring cleaning staff are correctly trained poses a greater challenge as these staff are recruited from an external agency who are responsible for their own training and quality control; however, the health and safety officer has worked with this agency to ensure that staff are familiar with safety procedures. No sand or other inert absorbable material was available in the office in case of large spillages. This has now been obtained and all staff are familiar with where this is stored.
A small, lockable cupboard was previously used for storing cleaning products but this was sometimes left unlocked. Furthermore, containers of kitchen cleaner were left in the cupboard under the sink in the kitchen close to where clean crockery is stored, and toilet cleaner was also frequently left in toilet cubicles. The COSHH assessment identified that Lifeguard 3 Way Toilet Cleaner should be kept away from chlorine-releasing agents and sodium hypochlorite; therefore bleach and toilet cleaner should not be stored together in the same cupboard as there is a risk that they may come into contact (e.g. in case of spillage). A second, lockable cupboard suitable for the storage of these chemicals will be purchased with one month and the two products stored separately. Staff will be trained to ensure that no products are left lying around in the kitchen or toilet areas and are returned to the storage area after each use, which should always be kept locked.
The disposable cloths used for cleaning the kitchen were previously being rinsed with water after use, left to dry and re-used. In order to minimise the risk of exposure of office staff to the cleaning product, these cloths will now be disposed of after a single use. Protective overalls worn by cleaning staff will be washed on a weekly basis and PVC/rubber gloves changed regularly.
Regular inspections are now carried out by the office health and safety officer on a monthly basis to ensure correct procedures are being followed.
Everyday cleaning products used in the office can pose a potential hazard to workers. It is therefore important that COSHH assessments are performed to assess the risk posed by the chemicals contained within these products. All workers should be aware of the correct procedures for the safe handling, use and disposal of these chemicals and should take the necessary precautions to minimise their risk of exposure (e.g. through use of personal protective equipment where appropriate).
Reference list
Health and Safety Executive 2007. List of approved workplace exposure limits. Retrieved 26th September 2008 from:
Piney, M. 2001, ‘OELs and the effective control of exposure to substances hazardous to health in the UK (version 3)’. Retrieved 26th September 2008 from:
The Physical and Theoretical Chemistry Laboratory 2008, Chemical and other safety information. Oxford University. Retrieved 26th September 2008 from:
Health and Safety Executive 2008. Control of Substances Hazardous to Health – COSHH. Retrieved 26th September 2008 from:
Health and Safety Executive 2008. COSHH: A brief guide to the regulations. Retrieved 26th September 2008 from:
Table 1. Chemicals used in office cleaning products: toxicity, target organs and recommended exposure limits (Health and Safety Executive 2007).



Target organs and organ systems

Workplace exposure limit

Long-term exposure limit

Short-term exposure limit

Freshline Bleach
Sodium hypochlorite solution (

Poses little hazard if stored correctly
Inhalation of chlorine-containing vapour may cause irritation to nose, throat and lungs
Repeated or prolonged contact of the concentrated solution with the skin may cause irritation and eventual dermatitis
Contact with the eyes may cause irritation and inflammation
Ingestion may cause irritation to mouth, throat and stomach

Eyes, skin, respiratory system, digestive system

Chlorine 0.5 ppm

Chlorine 1 ppm

Mr Muscle Professional Kitchen Cleaner
2-Butoxyethanol (

Cleaner is unlikely to be an irritant during normal use; prolonged contact with the skin may cause irritation

Skin (prolonged contact only)

25 ppm 1000 ppm

50 ppm None listed

Lifeguard 3 Way Toilet Cleaner
Phosphoric acid (5-15% v/v) Alkyl alcohol ethoxylate (

Contact with the eyes may cause severe irritation with risk of serious injury Contact with the skin may cause irritation Inhalation may cause irritation to nose, throat and lungs
Ingestion may cause irritation to mouth, throat and stomach

Eyes, skin, respiratory system, digestive system

None listed 2 ppm None listed

None listed 4 ppm None listed

Assessment Reference:
Date:26th July 2008
Review Date: 25th July 2009
1) Assessor Details [Client: please complete Section 1]

2) Process Description [Client: I’ve included all three products in one assessment – you may prefer to put each on a separate COSHH assessment pro forma]

Materials Used In Process

Risk Phrases (R)

Safety Phrases (S)

Freshline bleach
Sodium hypochlorite solution (Mr Muscle Professional Kitchen Cleaner 2-Butoxyethanol (Lifeguard 3 Way Toilet Cleaner Phosphoric acid (5-15% v/v) Alkyl alcohol ethoxylate ( 

R31 (contact with acid liberates toxic gas) R34 (causes burns) None required R41 (risk of serious damage to eyes) R38 (irritating to skin)

S2 (keep out of reach of children)
S2 (keep out of reach of children) S26 (in case of contact with eyes, rinse immediately with plenty of water and seek medical advice) S2 (Keep out of reach of children) S26 (in case of contact with eyes, rinse immediately with plenty of water and seek medical advice) S28 (after contact with skin, wash immediately with plenty of water) S37/39 (wear suitable gloves and eye/face protection)

[Client: the codes for both risk phrases and safety phrases are standard for COSHH assessments and were taken from The Physical and Theoretical Chemistry Laboratory, Oxford University website, accessed from: http://msds.chem.ox.ac.uk/]
3) Specific Considerations

Hazards Identification

Protective Equipment Required

Freshline Bleach
Contact with acids liberates toxic chlorine gas Inhalation of chlorine-containing vapour may cause irritation to nose, throat and lungs
Repeated or prolonged contact of the concentrated solution with the skin may cause irritation and eventual dermatitis
Contact with the eyes may cause irritation and inflammation
Ingestion may cause irritation to mouth, throat and stomach
Mr Muscle Professional Kitchen Cleaner Prolonged contact with the skin may cause irritation Lifeguard 3 Way Toilet Cleaner Contact with the eyes may cause severe irritation with risk of serious injury Contact with the skin may cause irritation Inhalation may cause irritation to nose, throat and lungs
Ingestion may cause irritation to mouth, throat and stomach

PVC or rubber gloves, protective overall and eye shield should be worn when handling concentrate; respiratory protection not required Personal protective equipment not typically required Eye protection required when handling neat product; other personal protective equipment not normally required

Specific First Aid

Specific Spillage Actions

Freshline Bleach
Keeping eyes open, immediately irrigate with water or eyewash for at least 10 mins; obtain medical advice immediately
Skin contact Remove contaminated clothing; wash thoroughly with plenty of running water; obtain medical advice if symptoms develop
If exposed to chlorine gas or other vapours, individual should obtain fresh air; obtain medical attention
Do not induce vomiting; if individual is conscious, wash out mouth with water and give water to drink; obtain medical attention immediately Mr Muscle Professional Kitchen Cleaner Eyes Rinse immediately with copious amounts of water, holding the eyelids open; obtain medical attention immediately Skin contact Wash thoroughly with soap and water Inhalation Remove individual from source of exposure Ingestion Do not induce vomiting; remove product from mouth; give the individual a small amount of water to drink; obtain medical attention Lifeguard 3 Way Toilet Cleaner Eyes Rinse immediately with plenty of water holding the eyelids open; seek medical attention immediately Skin contact Wash thoroughly with soap and water Inhalation Remove individual from source of exposure Ingestion Do not induce vomiting; remove product from mouth; give the individual a small amount of water to drink; obtain medical attention

Small spillages: dilute with plenty of water Large spillages: absorb with sand, earth or granules (do not use sawdust or paper) and dispose with a licensed waste management company; wash down site of spillage with water Hose site of spillage with plenty of water to dilute to at least 2.5% unless this would contaminate either a water course or vegetation – in this case, either (1) collect the spilt solution, dilute as above and pour down a waste water drain or sewer or (2) absorb with sand, earth or granules and dispose with a licensed waste management company Hose site of spillage with plenty of water to dilute to at least 2.5% unless this would contaminate either a water course or vegetation – in this case, either (1) collect the spilt solution, dilute as above and pour down a waste water drain or sewer or (2) absorb with sand, earth or granules and dispose with a licensed waste management company


Disposal method


Freshline Bleach Rinse out all containers with water before disposal Mr Muscle Professional Kitchen Cleaner Dilute small quantities with water (to at least 2.5%) and pour down a wastewater drain; rinse out all containers at least twice and either recycle or dispose of as commercial waste Lifeguard 3 Way Toilet Cleaner Dilute small quantities with water (to at least 2.5%) and pour down a wastewater drain; rinse out all containers at least twice and either recycle or dispose of as commercial waste. For larger quantities, dispose as commercial waste

4) Hazard Category

Hazard Category

Hazard Description

Freshline Bleach Medium Mr Muscle Professional Kitchen Cleaner Low
Lifeguard 3 Way Toilet Cleaner
Medium Hazard

Irritant; contact with acid liberates toxic chlorine gas (see risk phrases above) Eye and skin irritant (see risk phrases for component chemicals above)

I have familiarised myself with the risks created and safe working practices during the use and handling of chemicals. I shall adhere to COSHH regulations and safe laboratory practices as explained to me during the COSHH assessment.