Reviews of Environmental Contamination and Toxicology

Volume 160 of the series Reviews of Environmental Contamination and Toxicology pp 1-129

Chlorpyrifos: Ecological Risk Assessment in North American Aquatic Environments

  • John P. GiesyAffiliated withDepartment of Zoology, National Food Safety and Toxicology Center, and Institute for Environmental Toxicology, Michigan State University
  • , Keith R. SolomonAffiliated withDepartment of Environmental Biology, Centre for Toxicology, University of Guelph
  • , Joel R. CoatsAffiliated withDepartment of Entomology, Iowa State University
  • , Kenneth R. DixonAffiliated withInstitute of Environmental and Human Health, Texas Tech University
  • , Jeffrey M. GiddingsAffiliated withSpringborn Laboratories
  • , Eugene E. KenagaAffiliated with

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The objective of this risk assessment was to determine the probability and significance of effects of the organophosphate insecticide, chlorpyrifos, on aquatic ecosystems in North America. The assessment addressed both agricultural and nonagricultural uses. However, the primary focus of the risk assessment was agricultural ecosystems, especially row crops and, in particular, the “corn-belt” agroecosystems. The risk assessment also addressed potential effects from other agricultural uses as well as urban uses such as turf, termiticide, and home use. Exposure and effects in freshwater and saltwater environments were considered. Aquatic invertebrates and fish were included in the assessment, but amphibians, reptiles, birds, and mammals were not. The potential exposure of these organisms is small because of a lack of biomagnification of chlorpyrifos. Thus, if their prey are not affected, it is unlikely that organisms at higher trophic levels would be adversely affected. Measurements of chlorpyrifos residues in fish have shown both low probability and low concentrations of exposure (USEPA 1992b). Insufficient data on amphibians were available for a direct assessment of risks. A risk assessment of chlorpyrifos in terrestrial ecosystems was conducted in parallel with this aquatic risk assessment (Kendall et al., in manuscript). Chlorpyrifos is not used in isolation, and residues of other substances with the same mechanism of action may co-occur with chlorpyrifos and some of these may display additive toxicity (Bailey et al. 1997). Although the presence of these compounds could influence the overall conclusions of a risk assessment for the class of anticholinesterase insecticides, the extensive resources necessary to conduct a classwide review were not available and they were excluded from this evaluation.