Environmental Toxicology

Environmental toxicology provides information on the hazards posed by a pesticide to non-target plants and animals, both on land and in bodies of water. It involves evaluating data on lethal and sublethal effects in acute and chronic toxicity laboratory tests on a selected range of standard-test organisms. The concentration at which 50 percent mortality occurs is defined as the median lethal concentration (LC⁵⁰). The concentration at which there is no observed adverse effect is defined as the no observed effect concentration

Effects on non-target terrestrial species

Manufacturers are required to provide environmental toxicology data on the effects of their pesticides on birds, invertebrates and plants. Among birds, the bobwhite quail and mallard duck are typical test species. Acute and chronic oral and dietary toxicity tests and reproduction tests are conducted with each of the two species. The reproduction test is designed to check for the mortality of adults and chicks (both hatched and unhatched), as well as such sublethal effects as reduced egg production and thin eggshells.

Effects on wild mammals are predicted from the mammalian toxicology risk assessment. This assessment entails a review of acute oral, dermal and inhalation toxicity, short-term toxicity, long-term toxicity, genotoxicity, reproductive toxicity and teratogenicity studies.

Laboratory studies are also conducted to determine toxicity to:

• earthworms, which are important for soil fertility;
• invertebrates, such as bees and other insect pollinators;
• predatory or parasitic insects and predatory mites; and
• non-target terrestrial vascular plants.

Effects on non-target aquatic species

Acute- and chronic-toxicity tests are conducted with both cold- and warm-water fish species (rainbow trout and bluegill sunfish, respectively). Data on toxicity to marine fish are reviewed when relevant to the proposed use-pattern.

Information on acute and chronic toxicity to aquatic arthropods, such as water fleas (Daphnia species) is reviewed because of the important role these and other invertebrate species play in the aquatic ecosystem. Effects on molluscs (shellfish) are evaluated for pesticide uses that involve deposition in marine environments. Results of toxicity tests on freshwater and marine algae and aquatic vascular plants are also evaluated.