Publication Summary

During 1995, the Washington State Department of Ecology conducted a survey to assess concentrations of the pesticide DDT and its breakdown products DDD and DDE in edible fish tissues (muscle fillets) from Osoyoos Lake in north-central Washington. Species analyzed were yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieui), mountain whitefish (Prosopium williamsoni), carp (Cyprinus carpio), and lake whitefish (Coregonus clupeaformis). Two whole body samples of large scale sucker (Catostomus macrocheilus) and one smallmouth bass fillet were also analyzed for additional bioaccumulative pesticides and PCBs.

During 1995, the Washington State Department of Ecology conducted a survey to assess concentrations of the pesticide DDT and its breakdown products DDD and DDE in edible fish tissues (muscle fillets) from Osoyoos Lake in north-central Washington. Species analyzed were yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieui), mountain whitefish (Prosopium williamsoni), carp (Cyprinus carpio), and lake whitefish (Coregonus clupeaformis). Two whole body samples of large scale sucker (Catostomus macrocheilus) and one smallmouth bass fillet were also analyzed for additional bioaccumulative pesticides and PCBs.

Mean concentrations of total DDT (t-DDT; DDT+DDD+DDE) in muscle fillet ranged from 60 ng/g (parts per billion) in yellow perch to 1,110 ng/g in lake whitefish. Carp had the second highest t-DDT concentrations in muscle (437 ng/g), followed by mountain whitefish (105 ng/g), and smallmouth bass (73 ng/g). PCBs, hexachlorobenzene (HCB), and DDMU, a further breakdown product of DDT, were detected at low concentrations (? 60 ng/g) in whole fish.

Results were compared to criteria for the protection of human health, wildlife, and aquatic life. t-DDT concentrations in all species exceed the level expected to result in a 10-6 excess cancer risk, by factors of 1.9 to 35. Levels of t-DDT in whole suckers exceed several criteria to protect piscivorous birds and mammals. Recommendations are as follows:

1. To retain Osoyoos Lake on the "water quality limited" 303(d) list for DDT;

2. Conduct a site-specific health risk assessment for consumers of Osoyoos Lake fish;

3. Distribute the report to fish & wildlife officials concerned with predatory bird populations in the Okanogan basin; and

4. Implement source control recommendations detailed in an earlier study on DDT sources to the Okanogan River and Osoyoos Lake.

Link to EIM data for User Study ID DDT-OSOY