Health Risk Assessment of Xylene through Microenvironment Monitoring Data: A Case Study of the Petro-Chemical Industries, Thailand

In the absence of environmental health epidemiology, risk managers, policy makers and health-care authorities usually rely on estimates of human exposure level of proximity to hazardous waste site or regional ambient air quality data. Based on ambient concentrations without considering time-activity patterns, the estimation of personal exposure may be over-or underestimated. Twelve villages surrounding the petro-chemical industries located in the eastern region of Thailand were randomly selected to be a representative study area. In each village, air samples were collected at thirty-one microenvironments including indoor and outdoor of a household and workplace. The time-activity patterns of the commuters were also recorded. The ambient xylene concentrations were determined by thermal desorption gas chromatograhy/mass spectrometry. The indoor samples were determined by gas chromatography flame ionization detector. Commuters living in the vicinity of the industrial areas spent most of the time indoor (93.2%), especially at home (66.8%). Individuals spent a significant fraction of the day indoors. The concentrations of xylene ranged from less than 1 μg/m3 to 291.3 μg/m3. The highest level was found at the auto repair shop (291.3 μg/m3). Given micro-environmental concentrations and activity times, the average concentrations of xylene to which commuters may be exposed daily ranged from 90.62 to 134.75 μg/m3. The long term exposure level via inhalation was found to be very low. Collectively, no hazard was indicated by the hazard quotient and the results were found to be similar in all villages