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P.O. Box 42560
1111 Washington ST SE
Olympia, WA 98504-2560
Phone: (360) 902-1800

Department of health data review

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Department of Health Data Review


The Washington State Department of Health requires municipal well operators to collect and test groundwater samples. This is the only active statewide groundwater monitoring program in Washington that includes pesticide testing. More information is available through the Department of Health’s Office of Drinking water. WSDA reviews this data every year and compares amounts of any legacy and current-use pesticides found to drinking water criteria set by the Environmental Protection Agency. We publish information from our review every other year and plan activities based on these results and our Pesticide Management Strategy [PDF, 3.7 MB].

2021 — 2022 Data

Between January 1, 2021 and December 31, 2022 the Department of Health tested 2,561 wells for pesticides, most of them once or twice during the two years. Out of 86 pesticides and pesticide-related chemicals tested for, the Department of Health found 13 different chemicals in well samples.
  • Two of these chemicals were higher than EPA’s drinking water criteria (DCPA acid metabolites and ethylene dibromide).
  • Four of these chemicals were detected above 20% of an EPA drinking water criteria (Bromomethane, Pentachlorophenol, DCPA acid metabolites, and ethylene dibromide).
  • Ethylene dibromide was canceled in 1983.  Bromomethane, also referred to as methyl bromide, is being phased out and use is expected to decline as alternatives are available. Pentachlorophenol, or PCP, is also being phased out with a full ban expected by 2027.
  • DCPA acid metabolites are breakdown products of the herbicide dacthal, and were found in wells in Grant County and Walla Walla County.
  • Evaluations of DCPA are ongoing as it continues to be detected at elevated concentrations in Washington State.

 

2019 — 2020 Data

During January 1, 2019 through December 31, 2020 the Department of Health tested more than 2,000 wells, most of them once or twice during the two years. Out of 87 pesticides and pesticide-related chemicals tested for, the Department of Health found 13 different chemicals in well samples.
  • Three of these chemicals were higher than EPA’s drinking water criteria (DCPA acid metabolites, dinoseb, and ethylene dibromide).
  • Four of these chemicals were at levels high enough to be covered by WSDA’s Pesticide Management Strategy (1,2-dichloropropane, DCPA acid metabolites, dinoseb, and ethylene dibromide).
  • Ethylene dibromide was canceled in 1983, dinoseb was canceled in 1986, and 1,2-dichloropropane is not currently registered for use in Washington, but may be present in small amounts in other products.
  • DCPA acid metabolites are breakdown products of the herbicide dacthal, and were found in wells in Grant County and Walla Walla County.
  • We have done special studies in these counties and will keep working with the Department of Health on regional projects to learn about how pesticides are reaching groundwater and what we can do to prevent it.