Publication Summary

Twenty-four fish tissue samples were collected from eight sites in September 1995 for the Washington State Pesticide Monitoring Program (WSPMP). Samples were analyzed for 44 target pesticides and breakdown products, and five polychlorinated biphenyls (PCBs). Total lipid content was also determined for each tissue sample.

Twenty-four fish tissue samples were collected from eight sites in September 1995 for the Washington State Pesticide Monitoring Program (WSPMP). Samples were analyzed for 44 target pesticides and breakdown products, and five polychlorinated biphenyls (PCBs). Total lipid content was also determined for each tissue sample.

A total of 24 pesticides and breakdown products, as well as two PCBs (Aroclor equivalents), were detected in the fish. DDT or its breakdown products, DDD and DDE, were found in all 24 samples. Hexachlorobenzene was detected in 21 samples, dieldrin in 16, and chlordane or its breakdown products in 15 samples. Four of the detected compounds – chlorpyrifos (Lorsban), DCPA (Dacthal), endosulfan (Thiodan), and trifluralin (Treflan) – are currently registered for use in Washington. Pentachlorophenol is also still used, and its breakdown product, pentachloroanisole, was found in six samples.

Results were compared to USEPA human health screening values and proposed wildlife criteria. Screening values were exceeded for one or more compounds at seven of the eight sites. Total DDT, dieldrin, and PCBs were above screening values in samples from six, five, and four of the sites, respectively. Total DDT and aldrin/dieldrin levels exceeded proposed wildlife criteria at three of the four sites where samples were analyzed as whole fish.

Four sites were sampled in the Mid-Columbia area to assess the distribution of pesticide contamination in this popular sport-fishing destination. Results from whole-fish analyses support conclusions reached by the U.S. Geological Survey that concentrations of some pesticides may pose a threat to fish and wildlife. Concentrations of total DDT and dieldrin in bass fillets were consistently high in waterbodies receiving irrigation return water. Levels of most pesticides were substantially lower in smaller fish, indicating that fishermen can reduce their risk by not eating large fish. Pesticide concentrations are also considerably lower in fish from seep lakes that do not receive direct inputs from irrigation return water.

Recommendations include (1) an intensive survey of sport fish from waterbodies within the Columbia Basin Irrigation Project area to satisfy data requirements for a human health risk assessment, and (2) addition of Cowiche Creek to the lower Yakima River "area of concern" as defined by a Washington State Department of Health recommendation to eat fewer bottom fish contaminated with DDT from the river.

Link to EIM data for User Study ID WSPMP95T