Selected organochlorine pesticide and polychlorinated biphenyl residues in house dust in Singapore.

Although the use of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) has been prohibited in Singapore since 1980, OCPs and PCBs still can be detected in the environment and represent a potential threat to public health. In this study, OCPs and PCBs were measured in house dust samples collected from 31 homes across the island-state of Singapore. Organochlorine pesticides, such as hexachlorocyclohexanes (HCHs), chlordanes and dichlorodiphenyltrichloroethanes (DDTs) were tested, with a range of <LOD to 240ngg(-1) dust, <LOD to 110ngg(-1) dust and <LOD to 770ngg(-1) dust, respectively. Of 41 target PCB congeners measured, 28 were detected, and the median level of SigmaPCBs was 5.6ngg(-1) dust. The prevalence of these pesticides and industrial chemicals which have been banned many years ago suggests limited indoor degradation and on-going environmental accumulation. Weak negative correlations between an increased elevation of the residence and the concentration of DDTs and some low-chlorinated PCB congeners were noted, most likely due to increased ventilation and distance from ground-based sources at higher floors. Levels detected in several studies conducted in the USA were several orders of magnitude higher than concentrations observed in Singapore. Heavier use of chlorinated products in the USA, as well as different sampling methods, sampling time and site characteristics are likely explanations for the observed differences. Daily human intake of OCPs and PCBs via house dust was calculated, but values were low compared with dietary data from overseas. Ingestion of dust is indeed an exposure passway for these organochlorines, but may not be the predominant one.