Publication Summary

Initiated in 1991 by the Department of Ecology, the Washington State Pesticide Monitoring Program (WSPMP) analyzes ground water, surface water, fish tissue, and sediments for pesticide residues. The results of these analyses are used to provide information on how these residues are distributed in the environment and how these patterns are changing over time.

Initiated in 1991 by the Department of Ecology, the Washington State Pesticide Monitoring Program (WSPMP) analyzes ground water, surface water, fish tissue, and sediments for pesticide residues. The results of these analyses are used to provide information on how these residues are distributed in the environment and how these patterns are changing over time.

WSPMP surface water samples were collected at seven sites in April, June, August, and September of 1995. Samples were collected monthly at four additional sites from March through September in conjunction with the Yakima River total maximum daily load (TMDL) study performed in 1995 by Ecology′s Watersheds Assessments Section. Sites were selected to represent various pesticide uses, including use (1) by irrigated agriculture in the Columbia Basin and Yakima Valley, (2) on cranberry farms on the Washington coast, (3) in urban and suburban areas, and (4) by forest practices (Christmas tree farms).

Samples were analyzed for 161 pesticides and breakdown products in the following chemical groups: chlorinated pesticides, organo-phosphorus pesticides, nitrogen-containing pesticides, pyrethroid pesticides, chlorinated herbicides, and carbamates. Conventional parameters measured included total suspended solids, total organic carbon, conductivity, nitrate+nitrite, temperature, pH, and flow.

Thirty-nine pesticides and breakdown products were detected in WSPMP samples. Seven additional compounds were found in samples for the Yakima River TMDL. The most frequently detected pesticides were 4,4′-DDE, azinphos-methyl, chlorpyrifos, 2,4-D, atrazine, simazine and terbacil. Washington State and/or USEPA aquatic life criteria were exceeded at four WSPMP sites, and all four of the Yakima River TMDL sites. Pesticides above criteria were total DDT, azinphos-methyl (Guthion), chlorpyrifos (Dursban, Lorsban), and malathion. Levels of carbaryl, diazinon, and endosulfan exceeded National Academy of Sciences (NAS) recommended maximum concentrations to protect aquatic life and wildlife.

Pesticide use on cranberries in the Grayland area resulted in a high number and frequency of detections in Grays Harbor County Drainage Ditch No.1 (GHCDD-1). Five insecticides and five herbicides were found in all four sample periods. Five insecticides were detected at concentrations exceeding water quality criteria, three of these at the highest levels ever recorded in the state. These results prompted an intensive survey in 1996 to assess pesticide contamination from cranberry bog drainage in the Grayland area.

A large number of pesticides were also detected in Crab Creek Lateral and EL68D, 16 and 19 respectively. These streams are irrigation returns in the Mid-Columbia Basin. Concentrations of three insecticides from Crab Creek Lateral and two from EL68D were above water quality criteria. Effects from the combination of all these pesticides are unknown, but are likely to be greater than individual effects.

Azinphos-methyl and chlorpyrifos were found at concentrations above water quality criteria in samples from Cowiche Creek, which drains orchards northwest of Yakima. Similar levels of these two pesticides have been found in other streams in Washington adjacent to orchards, indicating that label requirements and/or application techniques for tree fruit are not adequate to keep these pesticides out of surface waters.

High concentrations of total DDT and azinphos-methyl were detected in a majority of the samples collected from the Yakima River and three of its tributaries. Other insecticides found included carbaryl, chlorpyrifos, diazinon, and malathion. Guidelines outlined in the report for the Yakima River TMDL should reduce levels of total DDT in the water column below state standards by reducing suspended sediment to which DDT binds. However, azinphos-methyl and the other currently used insecticides are probably not bound to sediment particles and may continue to be a problem after sediment controls are in place. Recommendations include: 1. An assessment of irrigation returns in the Mid-Columbia Basin to determine how pesticides are affecting aquatic life and wildlife in the basin. 2. Changes to pesticide application techniques for tree fruit to keep insecticides out of surface waters and subsequent monitoring to evaluate the effectiveness of new techniques. 3. Periodic monitoring of streams in the Yakima Valley to determine if BMPs developed to reduce suspended sediment are helping to reduce concentrations of currently used pesticides

Link to EIM data for User Study ID WSPMP95W