Cancer risk analysis of benzene , formaldehyde and acetaldehyde on gasoline station workers

Background: Benzene, formaldehyde and acetaldehyde are carcinogenic substances to which gasoline station workers are most likely exposed via inhalation. To evaluate these compounds in the ambient air of gasoline stations, the inhalation exposure test on workers was performed and assessed. By the appropriate intervention of wearing mask and hand washing during work shift, we determined whether or not there is cancer risk to the exposure of benzene, formaldehyde and acetaldehyde using urinary biomarkers. Methods: A cross sectional study was conducted in 38 workers of 6 gasoline stations in Pathumwan District, Bangkok, Thailand. Inhalation and ambient air concentrations of benzene, formaldehyde and acetaldehyde were evaluated by GC/FID and HPLC/UV detectors. Urinary trans, trans-muconic acid (t,t-MA), formaldehyde and acetaldehyde concentrations detected in gasoline workers before and after appropriate intervention were analyzed by GC/FID. Results: The average inhalation exposure concentrations of benzene, formaldehyde and acetaldehyde were 195.56, 12.60 and 5.74 μg/m3, respectively. The level of benzene exposure was significantly higher than the ambient air level (independent t-test, p < 0.01). The average lifetime cancer risk of the workers exposed to benzene, formaldehyde and acetaldehyde was determined at the values of 2.15E-04, 1.27E-05 and 2.69E-06, respectively. Benzene and formaldehyde values were higher than an acceptable criteria defined as 1E-06. The amount of urinary t,t-MA, formaldehyde and acetaldehyde in the workers daily after 7-days appropriate intervention (wearing masks as personal protective equipment (PPE) and hand washing) was decreased. Formaldehyde and acetaldehyde, which were detected in urine, showed significantly lower than before intervention (pair t-test, p < 0.001). Conclusions: Results from our study confirmed that the gasoline workers have high chances of cancer risk from daily exposure to benzene and formaldehyde. The urinary’s t,t-MA, formaldehyde and acetaldehyde could be considerably used as biomarkers in gasoline station workers. An appropriate intervention, using PPE and hand washing, could reduce the cancer risk. © 2012 Tunsaringkarn et al; licensee Herbert Publications Ltd. This is an open access article distributed under the terms of Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0),This permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited *correspondence: tkalayan@chula.ac.th 1College of Public Health Sciences, Chulalongkorn University, Bangkok 10330, Thailand. Full list of author’s information is available at the end of the article Background Volatile organic compounds (VOCs) are generated through fuel used and its evaporation. The refueling of vehicles is a major source of VOCs in the ambient air [1]. Aromatic hydrocarbon levels are high particularly in specific environments such as roadsides along busy streets, parking garages and gasoline stations. Gasoline workers are directly exposed to various gasoline products via many routes: ingestion and dermal absorption, but the most likely route is by inhalation [2]. In Bangkok metropolitan area, since 2001 after the banned of leaded-fuel, the number of gasoline station with the service of gasohol has been rapidly increased [3]. It has been reported that the exposure level at the gasoline station is largely dependent on the gasoline’s technical specifications such as the benzene content, emission control and the operation [4]. Because of increasing gasohol consumption, there has been an increase in carbonyl compounds, especially formaldehyde and acetaldehyde (both and benzene are designated as carcinogens [5]) in the general ambient air of Bangkok [6-7]. Exposure assessments of any toxic air pollutants could be used to evaluate the potential exposure to humans and the environment. The measurement of direct personal exposure is still a reliable method accessing the health impact of hazardous air pollutants [8]. It has been found that high doses of chemical exposure may overwhelm the metabolic capacity and resulted in the presence or remaining of metabolites and un-metabolites in urine. The urinary trans, trans-muconic acid (t,t-MA) is a metabolites of benzene, which is used as a biomarker of exposure [9] while formaldehyde is metabolized by aldehyde dehydrogenase into formic acid which is further oxidized to carbon dioxide or may serve as a one-carbon donor in tetrahydrofolate-dependent synthesis of purine, pyrimidine and amino acids. However, because of the rapid metabolism and exhalation, the exposure to formaldehyde does not always result in an increased blood or urine concentration of the parent compound in animals or humans [10-11]. Therefore, the development of urinary biomarkers for formaldehyde and acetaldehyde exposures could be another option for risk assessment and biomonitoring in occupational workers, along with the use of personal protection equipments (PPEs) by respiratory, hand and body in the work place as recommended by the Occupational Safety and Health Administration (OSHA) [12]. Journal of Environmental Engineering & Ecological Science ISSN 2050-1323 Tunsaringkarn et al. Journal of Environmental Engineering & Ecological Science 2012, http://www.hoajonline.com/journals/pdf/2050-1323-1-1.pdf 2 doi: 10.7243/2050-1323-1-1 In this preliminary study, we conducted the cancer risk analysis of benzene, formaldehyde and acetaldehyde on the gasoline station workers and compared these exposures between before and after the 7-days of appropriate intervention (of wearing mask and hand-washing), by using the urinary t,t-MA, formaldehyde and acetaldehyde will be used as biomonitoring. Methods Study area: Our study areas were 6 gasoline stations located in the Pathumwan district (one of the busiest areas with the most congested traffic and high level of air pollutions), Bangkok, Thailand. Sample collection and analysis: Samples were collected from 6 gasoline stations (Brand A: Station 1 & 2; Brand B: Station 2 & 3; Brand C: Satation 5 & 6) of Pathumwan district, from May to July 2010. Twenty-four workers (4 workers from each gasoline station) were examined for the inhalation exposure and thirty-eight workers were subjects for examinations of urinary t,t-MA, formaldehyde and acetaldehyde, before and after 7-days of appropriate intervention (wearing mask and hand washing practice (which the workers agreed that could protect the exposures and were easy to do) during their work shift. The personal mask used in this study was the 3M-9913V Type GP1 (Australia Pty Limited) with an exhalation valve (Australian Standard). The Dettol hygienic original soap (Reckite Benckiser, Thailand) was used for hand washing. All subjects were healthy and had worked for more than six months at their gasoline stations. They were interviewed for personal data, perception of the intervention practice and questioned to evaluate their personal air formaldehyde and acetaldehyde exposure using the same method as for the ambient air sampling. They were provided with a consent form before the study. Permission to conduct study on human subjects was approved by the Ethical Review Committee for Research Involving Human Research Subjects, Health Science Group, Chulalongkorn University. A total of twelve air samples through the active sampling method were collected for 8 h during working hour (6.00 A.M.2.00 P.M.). Air samplings were collected using 2,4 DNPH cartridge (for formaldehyde and acetaldehyde) and activated charcoal tube (for benzene) connected to a low flow personal air pump. Both cartridge and charcoal tube were kept at 4oC during transportation to the laboratory and were stored in a refrigerator until analysis. Air sample analysis: The 2,4-DNPH cartridge was extracted immediately after sampling, and eluted with acetonitrile (ACN). The extracted solution was analyzed for formaldehyde and acetaldehyde by the high performance liquid chromatography (HPLC) with a gradient mobile phase 60/40% of ACN/water at flow rate 1 mL/min. The detection was by ultraviolet (UV) detector at a wavelength of 360 nm [13]. For benzene, activated charcoal was extracted with carbon disulfide (CS2), and the sample solution was analyzed by the gas chromatography (GC) with flame ionization detector (FID). The starting temperature was set at 35oC and programmed to increase to 120oC at 5oC/min and then continued to increase from 120oC to 230oC at 20oC/min, with a temperature hold for 5 min at 230oC. Both injector and detector temperatures were maintained at 300oC. Urine samples analysis: Thirty-eight urinary samples (20-50 mL) were collected in glass containers, sealed and stored at -20oC before formaldehyde and acetaldehyde analyses by GC/FID [14]. All measured values were divided by urinary creatinine (Cr) concentration [15] for clinical chemistry analysis. The World Health Organization (WHO) has adopted guidelines for the acceptable limits of urinary creatinine concentrations between 0.3 and 3.0 g/L [5]. Cancer and non-cancer risk calculation: The inhalation exposures were estimated in terms of Chronic Daily Intake (CDI) for cancer and Exposure Concentration (EC) for non-cancer. The calculation of CDI and EC according to Risk Assessment Guidance for Superfund (RAGS) Part A and Part F approaches, respectively. They can be expressed as follow: CDI = CA x IR x ET x EF x ED/(BW x AT) EC = CA x ET x EF x ED/AT Where; CDI (mg/kg/d) = Chronic Daily Intake EC (μg/m3) = Exposure Concentration CA (mg/m3) = Contaminant concentration in Air IR (m3/h) = Inhalation Rate (0.875 m3/h assumed for adult) BW (kg) = Body Weight (60.54 kg, average body weight of workers) ET (h/d) = Exposure Time (8 h/d for workers) EF (d/y) = Exposure Frequency (350 d/y assumed for workers) ED (y) = Exposure Duration (30 y for workers) AT (d) = Averaging Time (70 y × 365 for cancer or ED × 365 for non-cancer) Cancer