Pesticides and Water Quality

New information on toxicity of fipronil to stream organisms

New information on toxicity of fipronil to stream organisms

The common insecticide fipronil and some of the compounds it degrades to are more toxic to aquatic insects, such as mayflies and stoneflies, than previously estimated, reports a new USGS study.

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Featured Study: Multiple Pesticides in U.S. Streams

Featured Study: Multiple Pesticides in U.S. Streams

A mix of multiple pesticides is common in many U.S. streams, reports a new study by the U.S. Geological Survey National Water Quality Program.

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Science Center Objects

Pesticides are chemicals designed to kill pests, including insects (insecticides), weeds (herbicides), and fungi (fungicides). The USGS assesses the occurrence and behavior of pesticides in streams, lakes, and groundwater and the potential for pesticides to contaminate our drinking-water supplies or harm aquatic ecosystems.

Pesticides are used in agriculture, in homes and businesses, on lawns and gardens, along roads, in recreational areas, and on pets and livestock. There are hundreds of different pesticide chemicals in use in the United States. In 2007, about 390 million kilograms (430,000 tons) of pesticides, including herbicides, insecticides, and fungicides, were used in the United States. Pesticides released into the environment for agricultural and nonagricultural purposes can contaminate surface water and  groundwater, which are critical sources of drinking water.

A national map that shows by color estimated concentrations of atrazine in shallow groundwater underneath agricultural land.

This map shows the predicted probability that the sum of concentrations of atrazine and its degradate deethylatrazine (DEA) will exceed 3.0 micrograms per liter (µg/L) in shallow groundwater underlying agricultural lands. Although shallow groundwater is unlikely to be used as a source of drinking water, the 3.0 µg/L threshold shown on this map is EPA’s drinking water standard (Maximum Contaminant Level) for atrazine.  About 95% of the nation’s agricultural areas have less than a 10% chance of exceeding this threshold. Atrazine is one of the most extensively used herbicides in the United States, with average annual use over 70 million pounds—primarily for corn and sorghum. (Credit: Paul Stackelberg, USGS)

The USGS, through its National Water Quality Program, researches numerous aspects of pesticides and water quality, and has developed maps, graphics, and tools to aid in understanding where pesticides occur, at what concentrations, and potential consequences.

  • Pesticide Use: The tables, maps, and graphs provided on this web site  provide estimates of agricultural pesticide use in the conterminous United States for hundreds of pesticides.

  • Trends in Pesticide Occurrence in Streams: Use the online tool to view a national maps of trends in pesticide concentrations in streams.

  • Concentrations of Pesticides in Water of Potential Human-Health Concern: This searchable online database provides Health-Based Screening Levels (HBSLs) for hundreds of chemicals, including  pesticides and degradates.

  • Pesticide Toxicity to Aquatic Organisms: The Pesticide Toxicity Index (PTI) can be used to assess the potential toxicity of pesticide mixtures in water to freshwater aquatic organisms. Benchmarks also are available for pesticides in sediment.

  • Pesticides and Stream Ecology: The Regional Stream Quality Assessment (RSQA) is assessing how chemical stressors, such as pesticides and nutrients, and physical stressors, such as disturbed streambanks  and sedimentation, are affecting the aquatic organisms that live in small streams across the United States.

  • Pesticides and Lake Sediment: Many pesticides dissolve in water, but some pesticides, like DDT and chlordane,  adhere to sediment and persist for years in the bed sediments of stream and lakes, recording the history of contaminant use in watershed.