Metabolites of organophosphorous insecticides in urine specimens from inhabitants of a residential area

The most frequently used pesticide in U.S. homes, as well as in schools and day care centers, is chlorpyrifos. In 1997, this insecticide was detected in household dust from the former U.S. Forces housing estates in Frankfurt am Main, Germany, resulting from its earlier use up to 1993, i.e., at least 4 years ago. This led to great concern in the new inhabitants. To investigate their internal exposure to the substance, they were offered the opportunity of taking part in biomonitoring examinations. Children playing on the floor were assumed to be especially at risk due to increased exposure to chlorpyrifos via oral or dermal intake. A total of 1146 inhabitants took part in this voluntary investigation. All of them stated that they had never used chlorpyrifos in their homes. Spot urine samples of the study participants were analyzed for six metabolites of organophosphorous insecticides [dimethylphosphate (DMP), diethylphosphate (DEP), dimethyl-thiophosphate (DMTP), diethylthiophosphate (DETP), dimethyldithiophosphate (DMDTP), and diethyldithiophosphate (DEDTP)] using a very sensitive gas chromatographic method with mass-selective detection and a limit of detection of 1 mug/L. No evidence was found of increased internal exposure due to former chlorpyrifos application in these homes (>4 years ago), either in children or in adults. The median values and 95th percentiles of the urinary metabolite concentrations in 484 adults were (mug/g creatinine): DMP, 15.5 and 102.5; DMTP, 13.5 and 125.8; DMDTP, <1 and 13.1; DEP, 2.1 and 11.6; DETP, <1 and 6.4; DEDTP, both <1. The urinary metabolite concentrations in children <6 years of age were higher; this was caused mainly by lower creatinine concentrations. To conclude, no increase in internal exposure due to former indoor application of chlorpyrifos could be found, and the reference values published for internal organophosphate exposure in adults in Germany were confirmed. However, as shown in other environmental studies, the urinary excretion of organophosphorous metabolites exceeds dietary intake several fold; this has been estimated from the data in various duplicate dietary studies. This observation calls for further investigation. (C) 2001 Academic Press