1. IntroductionIn many occupational settings, the ambient environment is a sink of various contaminants that emerge from point and nonpoint sources and causes direct exposure to workers. Such exposures in petroleum-related occupations usually result from routine transportation, distribution, accidental spills, improper handling and use, and leaching of petroleum hydrocarbons products; there are also many other ways by which humans are exposed to these chemicals . Many of the aromatic organic solvents, such as toluene, ethyl benzene, xylene, etc., are common components of petroleum products, most of which have already been confirmed as carcinogens, e.g., benzene [2-4]. Benzene is considered to be one of the possible causes of morbidities among automobile workshop mechanics as well as in automobile painters . Among many other environmental sources, benzene mostly arises from fuel vapors and gasoline (range, 1.8–3.7%) and from solvents used for degreasing or as diluents at work areas of automobile mechanics . Most exposures to organic solvents occur during the maintenance of various engine parts . Such solvents, after being absorbed into the intercellular fluid, may enter main bloodstream and get distributed throughout the body . Benzene affects blood production by affecting the bone marrow. In Korean industries, an excessive risk of hematopoietic diseases because of relatively high past exposure to benzene has been reported . Apart from direct occupational exposure, nonoccupational population around chemical factories and other occupational sites may also undergo indirect exposure . Thus, occupational exposure hematotoxicity  and other blood disorders such as blood cancer (leukemia), aplastic anemia, and dysplastic bone marrow conditions are common results of exposure to aromatics such as benzene , screening of which can be done easily by complete blood counts.Thousands of workers in Pakistan are routinely exposed to such chemicals, but no such data are available due to lack of proper reporting . Even local people who do not have any direct occupational exposure to chemicals may get exposed to varying levels of benzene from the ambient environment . Exposure studies are the most important steps toward identification and prevention of multiple risks that vary with occupational categories and job responsibilities. Many studies  have used demographic features such as age, gender, body mass index (BMI), smoking status, and consumption of certain types of contaminated food in exposure assessments. It is necessary to keep these features in focus while setting rules and regulations for potential hazardous occupations, which can be helpful in minimizing health risks. In developing countries such as Pakistan, creating awareness among workers about workplace chemicals and other related hazards should also be given priority. There should be thorough hazard assessments at a large scale to review occupational safety conditions at the initial stage, and practical measures should be taken to minimize them in future. This study was planned to evaluate the effects of continuous exposure to solvents, chemical contaminants, and other confounding factors that may cause functional changes in blood parameters. It may be helpful in future for suggesting the most significant priorities in the light of research outcomes, to minimize workplace- and occupation-related health risks, and to ensure safety to workers’ health.
2.1. Sampling sitesSampling was done at random at the visited study areas among car mechanics (MCs, n = 29), including diesel-engine mechanics, motor-truck mechanics, engine-repair mechanics, differential and brakes repairers, general automobile-service-station mechanics, workshop heads, and apprentices, and car spray painters (PNs, n = 25). Task reportedly performed by MCs included engine repair, oil changing, lubrication, basic maintenance of fuel systems, etc. and that by PNs were denting, abrading, cleaning, adjusting, aligning, assembling and disassembling, brushing, burning, cementing, chipping, fastening, filling, finishing, fitting, hammering, maintaining, pressing, repairing, sanding, scraping, soldering, and spraying, apart from painting task. Participants for an age-matched control group (CN, n = 24) were selected from nonchemical-related occupations of the same city. Selection criteria were age of >25 years and work experience of >2 years. Personal data of each participant were collected through short interviews using a questionnaire mainly based on multiple-choice questions. Major focus of the questionnaire was on demographic information of interviewees, such as height, age, BMI, education level, overall health, workplace environmental hygiene, socioeconomic status, smoking status, nature of job, work experience, and work hours, as well as on selfreported health and whether the interviewees suffer from any symptoms due to their occupation (Figures 1 and 2, Table 1).
2.2. Sample collection and analysisSamples were collected from workers willing to participate in this study during their routine work hours. About 3–4 mL venous blood from the antecubital vein of each participant was taken with the help of a 10-mL disposable plastic syringe and immediately transferred to a sterile vacutainer, containing potassium–EDTA anticoagulant. All samples were analyzed in the most immediate time. Analyses of selected parameters were performed using whole blood (approximately 50 μL automated) on digital Sysmex, an automated hematology analyzer (KX-21). Reagents used were diluents, a lytic reagent (500 mL), and an enzyme cleaner (2 × 50 mL). Systems were used to measure red blood cells (RBCs, in × 106/μL), white blood cells (WBCs, in × 106/μL), platelet counts (PCs, in × 106/μL), hemoglobin (Hb, in g/dL), packed cell volume (PCV, in %), and mean corpuscle volume (MCV, in ft).
2.3. Statistical analysisThe SPSS version 13 and Microsoft excel software were used for statistical analyses. The Student t test, Wilcoxon signed ranks test, and Welch tests were used for paired analysis to test the statistical significance difference of selected parameters among studied population, keeping in focus the assumption of parametric tests. The effect size (r) was calculated using t statistic values and (df) where applicable. The Chi-square test was used to compare the proportions of categorical variables. Stepwise regression analysis was used assuming blood parameters as dependent variables and personal features, behavioral characteristics, and jobrelated parameters as independent variables. A p value of <0.05 was considered statistically significant.
2.4. EthicsThe project was reviewed and approved by the ethical review committee of Quaid-i-Azam University, Islamabad, Pakistan. Only those individuals were recruited who were willing to participate and were clearly informed about the purpose of investigations and expected outcomes. All participants signed the written consent form. Sampling and logistic support for this research was granted by the ethical review committee of the university in collaboration with the Volunteer’s Social Welfare Organization (VSWO) (registered under Social Welfare Act 1961, Pakistan).
3.1. Demographic characteristics of respondentsAll male participants from exposed groups (MCs and PNs) and the unexposed (CN) group generally had a normal BMI level, and were of almost the same age, height, and weight (Table 1). Samples from occupationally exposed workers were collected during their routine hours, and none was found to be equipped with any type of self-protective equipment. Workers in the study groups (mechanics of automobile repair shops and painters) had poor socioeconomic backgrounds and very low levels of education. Most of them were not very aware of chemical-related hazards. Most of the painting workshops were situated amid or beside mechanical and spare-part workshops. Apart from petroleum products, materials used in a typical painting shop, e.g., diluents, binder, thinner, hardener, etc. contained chemicals such as isocyanate, and benzene and its derivatives such as toluene. However, in the mechanical workshops, the main contaminants included kerosene oil, petroleum products, and crude oil, and major contamination of workplaces and workers’ body parts was from the used gasoline engine oil. The smell of chemicals was unavoidable, and according to participants, despite wrapping clothing around the noses (self-made mask), it was a cause of severe headache and nausea, more specifically for spray-paint workers. Odor or smell from solvents may arise from volatile organic compounds (VOCs) used as tinting pigments and solvents that help stabilize the dispersion.
3.2. Laboratory data analysisLaboratory data showed that RBC count was much lower in PNs (4.84 ± 0.5) than in CN group (5.12 ± 0.4), and this difference was significant [t(47) = 2.12, p = 0.03, r = 0.29]; similarly, difference was recorded for MCs [4.75 ± 0.7, t(51) = 2.38, p = 0.021, r = 0.32]. Mean WBC counts were slightly higher in both PNs and MCs, but for the difference in WBC counts between PNs and CN group was larger (5.73 ± 1.1) and significant [t(47)=–2.63, p = 0.01, r = 0.35] than that between MCs and CN group. Mean Hb values were lower in both PNs and MCs than in CN group, and the difference in Hb values between PNs and MCs (14.82 ± 0.5, 14.7 ± 0.6) was greater and significant as compared to CN group [t(47) = 2.09, p = 0.042, r = 29, and t(51)=2.5, p=0.01, r=0.33 for PNs and MCs, respectively]. Mean MCV and PCV recorded were higher only in PNs than in CN group, which was significant [t(47) = –2.82, p < 0.01, r = 0.29 and t(47) = –2.28, p = 0.027, r = 31, respectively]. Combined data of both exposed groups (PNs and MCs) showed significant differences for RBC count (lower as compared to CN group) [t(76) = 2.42, r = 0.27, p=0.018], Hb count [t(76)=2.73, r=0.30, p < 0.01], and PCV [t(76) = –2.31, r = 0.26, p = 0.028]. Differences in other parameters were nonsignificant (Table 2). When exposed individuals were divided into smokers (SMs) and nonsmokers (NSs), it appeared that RBC count was significantly lower among exposed SMs as compared to exposed NSs [t(52) = 2.28, p = 0.027, r = 0.25] and also mean Hb value was much lower among SMs than among NSs from exposed groups (combined data) [t(52) = 2.71, p < 0.01, r = 0.30] (Table 3).When all data were subjected to categorical analysis for SMs and NSs, more significant results were recorded, i.e. [t(76) = 2.44, r = 0.26, p < 0.01] and p < 0.002, [t(76) = 3.14, p < 0.01, r = 0.33], for RBC and Hb counts, among SMs and NSs respectively (Table 3).
3.3. Logistic regression analysisAll blood parameters of exposed workers (combined) were also subjected to logistic regression analyses; each blood parameter was considered as a dependent variable, while age, work hour, work experience, smoking status, etc. were entered in stepwise regression analyses as independent variables. Of all blood parameters, the most significant predictors of decrease in hemoglobin and RBC counts were found to be smoking [F(2, 75) = 9.49, p < 0.01, R2 = 0.20 and F(2, 75) = 5.91, R2 = 0.13, p = 0.019 for Hb and RBC, respectively] and work experience [F(2, 75) = 9.49, p < 0.01, R2 = 0.20 and F(2, 75) = 5.91, R2 = 0.13, p = 0.02 for Hb and RBC, respectively] (Table 4). Smoking was found to be the most significant predictor of decreased Hb and RBC counts, which shows that among SMs risks of decrease in the Hb and RBC counts amount to 0.43 and 0.29 units, respectively, per unit increase in smoking, after adjusting for each year of work experience (p = 0.04).
4. DiscussionIn the present work, effects of complex aromatic mixture of solvents on blood parameters were studied for the first time in Pakistan; so far, no published data could be found on this subject. Influence of workplace environments on the extent of exposure and behavioral characteristics were also focused on among a selected occupational population. In Pakistan, workers’ safety and surveillance setup is a neglected subject. Despite a massive search, we could not find the guidelines for permissible exposure limits set by health authorities in Pakistan. People in such occupations are incapable of spending much for the betterment of self-health, neither does the government facilitate heath care; they bear poor socioeconomic status although they appeared physically healthy. In general, the poor do not seem to have a hazard-free future from a health perspective, especially in their workplaces. Almost all the participants in our study were found to be working without any proper personal protective equipment (Figures 1-3). In this study, the limited number of participants shows the difficulty in convincing people to participate and also in finding individuals who could meet the selection criteria. In our study, we found that most of the solvents used by both automobile MCs and PNs had benzene or its derivatives/by-products, and, apart from benzene constituents, participants reported the symptoms of isocyanate exposure, which was an important chemical in paint materials.
5. Conclusions and RecommendationsGood ventilation at workplaces ensures lower concentrations of benzene and other vapor-phase chemicals than poor ventilation. Poor ventilation, as defined by Liu et al , may be due to a low level of exhaust system or no exhaust at all which relies merely on natural ventilation. It is conclusive to suppose that more inhalable particles emerge around painting sites, and PNs may have low levels of dermal contact when using protective equipment; therefore, it is opined that most of the aerosols are inhaled by PNs at worksites. EPA guidelines  suggest that chemicals such as benzene at painting booths should be monitored for keeping exposure level minimum; for example, at paint sites air flow may be 8000 m3/h with a paint application rate of 2 L/h or air flow exhaust may also be 10,000 m3/h with a paint application rate of 2 L/h, in which maximum pollutant content (benzene) of paint equals 2.5% v/v. In our study, we found no rules and regulations regarding worker’s safety being practiced at any visited site; it appears reasonable to conclude that poor ventilation status at work areas seems to increase risks of exposure many times, since the release of chemicals into congested work areas seems to exceed the its rate of removal from there. On the basis of its results, the most important conclusion that this study has drawn deals with the hazardous occupational environments in Pakistan; hygiene conditions in such setups are potential exposure factors and risks to workers’ health, and workers’ knowledge regarding safety of the workplace and chemicals is insufficient. Exposure to a complex mixture of solvents, especially aromatics such as benzene and others such as isocyanate, may lead to serious hematological disturbance when there is a low standard of hygiene and lack of personal protective equipment usage in the workplace. Further study is needed to investigate the exclusive impacts of occupational environment and smoking on workers’ health. However, MCs contact with body parts of automobile engines, and handling tools etc. smear most of the body parts with petrochemical fractions. There must be a regular use of coveralls and gloves. It can be suggested that if workplace hygiene is properly maintained and workers’ exposure time is reduced by minimizing the working hours, exposure risks can be minimized significantly.