Environmental Health - Toxic Substances Hydrology Program

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Fungicides from Areas of Intense Use Detected in Streams and Groundwater

USGS scientists installing passive sediment samplers in an irrigation ditch
USGS scientists installing passive sediment samplers in an irrigation ditch near Hancock, Wisconsin. The samplers are designed to collect suspended sediment from streams over a 3-week period. Photo credit: Timothy Reilly, USGS.

U.S. Geological Survey (USGS) scientists have shown that many currently used fungicides are transported from areas of intense use to nearby streams and groundwater at concentrations that may be a concern for environmental health. This is the first study to document the presence of boscalid in groundwater, zoxaminde in sediments, and pyraclostrobin in suspended sediments.

Limited toxicological data are available on the effects of fungicides on nonpathogenic fungi that are important to stream ecosystems. However, some studies suggest that fungicides may be more toxic to freshwater biological communities, including beneficial fungi, than previously expected. The results of this study indicate the importance of including fungicides in pesticide-monitoring programs, particularly in areas where crops are grown that require frequent treatments to prevent fungal diseases.

Summary of Fungicides Detected

Twelve fungicides were detected in streams, including:

  • boscalid (72 percent),
  • azoxystrobin (51 percent),
  • pyraclostrobin (40 percent),
  • chlorothalonil (38 percent), and
  • pyrimethanil (28 percent).

Six fungicides were detected in sediments, including:

  • pyraclostrobin (75 percent),
  • boscalid (53 percent),
  • chlorothalonil (41 percent), and
  • zoxamide (22 percent).

Fungal infections of crops are a concern across the Nation because they can significantly reduce yields of many crops, including potatoes. Although more than 3,600 pesticide products containing fungicides are currently registered with the U.S. Environmental Protection Agency, few studies have investigated fungicide occurrence in the environment.

USGS scientists conducted an assessment of fungicide occurrence in three geographic areas (Presque Isle, Maine; Parma, Idaho; and Hancock, Wisconsin) where fungicides are used intensively. The scientists recently modified their analytical capabilities to include methods to analyze for 33 fungicides and 57 other currently used pesticides in water and sediment.

The scientists published results on fungicide occurrence in water and sediment in companion articles in Chemosphere and Science of the Total Environment. They found at least one fungicide in 75 percent of the surface waters sampled and in 58 percent of the groundwater wells sampled. They also found at least two fungicides in 55 percent of the bed sediment samples and in 83 percent of the suspended sediment samples that were collected.

This study was funded by the USGS Toxic Substances Hydrology Program.


Reilly, T.J., Smalling, K.L., Orlando, J.L., and Kuivila, K.M., 2012, Occurrence of boscalid and other selected fungicides in surface water and groundwater in three targeted use areas in the United States: Chemosphere, v. 89, no. 3, p. 228-234, doi:10.1016/j.chemosphere.2012.04.023.

Smalling, K.L., Reilly, T.J., Sandstrom, M.W., and Kuivila, K.M., 2013, Occurrence and Persistence of Fungicides in Bed and Suspended Solids from Three Targeted Use Areas in the United States: Science of the Total Environment, v. 447, p. 175-185, doi:10.1016/j.scitotenv.2013.01.021

Elskus, A.A., 2012, Toxicity, sublethal effects, and potential modes of action of select fungicides on freshwater fish and invertebrates: U.S. Geological Survey Open-File Report 2012-1213, 42 p.

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