Longitudinal exposure to selected pesticides in drinking water

The presence and temporal fluctuations of concentrations of insecticides an d herbicides in natural waters has been well documented. Little, however, i s known about exposure to pesticides through drinking water for the general population. Concentrations of ten pesticides, including 4,4'-DDE and atraz ine, were measured up to six times at equally spaced intervals over a 1-yea r period in drinking water of 80 randomly selected residences in Maryland. Atrazine was detected in 228 (57.9%) of the drinking water samples with a m ean of 0.15 mu g/L, with standard deviation 0.12 mu g/L, median 0.17 mu g/L , and range <0.037 to 0.46 mu g/L. 4,4'-DDE was found in 22 (5.6%) water sa mples; no other target analytes were detected. Concentrations of atrazine i n drinking water were found to vary over a 12-month period with the greates t concentrations in the late summer and fall and the lowest in the early sp ring. Atrazine concentrations in drinking water were influenced more by dif ferences in levels among residences than by time of year. Seven-day average exposures and exposures per unit body weight to atrazine in drinking water exhibited a similar temporal pattern. Among individuals, drinking water co nsumption rate was a more important determinant of atrazine exposure (mu g/ d) and exposure per unit body weight (mu g/kg/d) than atrazine concentratio n in drinking water or body weight.