Environmental Risk Assessment

Scientific data on the environmental fate and environment toxicology of a pesticide are part of the information package required to support registration. Canadian environmental data requirements for major forestry and agricultural uses of chemical pesticides have been harmonized with U.S. requirements, and are similar to those of other pesticide regulatory systems. The Pest Management Regulatory Agency (PMRA) conducts a critical evaluation of these data to determine the environmental risk of a pesticide.

Risk assessment combines the results of the environmental toxicology (hazard) and environmental fate (exposure) assessments (i.e., the evaluation of the studies described above). The ratio of the No-Observed-Effect Concentration (NOEC) (for the most sensitive test species) to the expected environmental concentration is determined. A large ratio indicates a large margin of safety, with a limited environmental impact expected. Many factors determine how large this ratio must be in order for the risk to be judged acceptable. As the ratio becomes small, concern increases. At a ratio of less than one, an environmental impact is expected.

The environmental risk posed by a pesticide is a function of:

• Environmental fate - i.e., what happens to the pesticide once it enters the environment, including expected environmental concentrations to which non-target organisms may be exposed; and
• Environmental toxicology - i.e., the hazards posed by the pesticide to non-target plants and animals, both on land and in bodies of water.