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.