Over 500 grab samples of finished drinking water and related raw water were assayed for 10 organochlorine pesticides, their metabolites, and related compounds. The samples were collected between March 1964 and June 1967 from 10 selected municipal finished water supplies whose source was either the Mississippi or the Missouri River. Both 100-ml. and 1-gallon sample sizes were assayed. Included is a statistical evaluation of the one-step extraction method using 1-gallon samples to which known amounts of the 14 compounds were added at levels ranging from 0.06 to 5.0 p.p.b. Over 40% of the finished water samples contained detectable dieldrin and more than 30% contained detectable endrin, p,p′-DDT, and p,p′-DDE. Twenty per cent of the 63 samples assayed for chlordan contained detectable concentrations; five of these were in excess of 0.25 p.p.b. Aldrin, HCE, and heptachlor were found only occasionally. No toxaphene nor methoxychlor was detected. © 1969, American Chemical Society. All rights reserved.
