Levels of Pesticides and Polychlorinated Biphenyls in Selected Homes in the Bangkok Metropolitan Region, Thailand

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Abstract
Past uses of hazardous chemicals in Thailand for agricultural and household purposes have resulted in their ubiquity in the environment. This study aims to characterize the levels of 41 target chemicals, including 25 organochlorine pesticides (OCP), of which 17 are persistent organic pollutant (POP) pesticides, 7 pyrethroids, and 9 polychlorinated biphenyls (PCBs) in 8 homes in the Bangkok Metropolitan Region (BMR). The study is the first of these types for Thailand, and was conducted during the dry season of 2006-2007. Samples were collected at three areas of the BMR, including urban, suburban, and rural for indoor and outdoor (I/O) air, as well as from deposits on floor surfaces. Airborne samples were taken over 24 h for both the gaseous and particulate matter phases and analyzed separately by GC-ECD following the U.S. EPA TO-10A method. Overall 35 out of 41 compounds were detected in the samples. The compounds were mostly detected and at higher levels in the gas phase, except for a few less volatile compounds, such as pyrethroids or DDT. Indoor air concentrations are higher than the outdoor levels for most chemicals; hence, the I/O ratios are mostly above 1.0, especially for rural homes. Among the OCPs, heptachlor was found at the highest concentrations for urban homes (5.2 +/- 3.1 ng/m(3) indoor and 2.6 +/- 0.4 ng/m(3) outdoor). PCB profiles were dominated by the lighter congeners, with the highest levels found for PCB31 (10.4 indoors in urban homes (ng/m(3))). Suspended matters were found to be high indoors in the rural homes, which may be linked to high-strength of indoor sources.