Ecotoxicological Risk Assessment of Pesticides in Terrestrial Ecosystems

With the increasing awareness of environmental protection worldwide, it is becoming more and more important to evaluate the effects of chemical substances on the natural environment. With pesticides being intentionally released into the natural environment to protect crops from harmful insects, weeds and pathogenic microorganisms, countries worldwide, with Europe and the United States taking the lead, have formulated regulatory procedures making environmental risk assessments indispensable registration requirements.1), 2) Among them, the assessment of ecological risk is utilized to formulate the policies and measures suitable for protecting the ecosystem by understanding the impact of chemical substances prior to their emission into the environment. The most important issue is accurate assessment of the risks to the organisms in the environment that make up the ecosystem. The assessment of the ecological impacts of pesticides is classified into assessments for aquatic ecosystems and assessments for terrestrial ecosystems in the area of pesticide application followed by migration. Methods for assessing the risks to aquatic ecosystems have been debated worldwide ahead of those for terrestrial ones because, in addition to its being comparatively easy to consider the single hierarchical structure from producers such as algae to multiple levels of consumers such as crustaceans and fish, these aquatic plants and animals are food. Terrestrial ecosystems, on the other hand, provide an opportunity (blessing) for all species, including humans, to survive, just like the aquatic ecosystems, and the assessment of pesticide impact therein becomes one of the most important issues in the safety assessment. However, evaluation of the risk to terrestrial ecosystems, which maintain interrelationships such as predation, prey, competition and parasitism among the wide variety of living species in a complex mixture of the environmental media of air, soil and water systems, is extremely high-level and complex when compared with evaluation of aquatic ecosystems. In addition, the mixing of a wide variety of ecosystems with unique structures and functions due to the everyday activities of people and the artificial connections with pesticides and agricultural activities is a factor that brings about further complexity as in the case of apiculture. Furthermore, there are many species of organisms for which the ecology is unknown, and the assessment of terrestrial ecological risks becomes more difficult because it is coupled with a paucity of toxicological knowledge on terrestrial organisms. To develop pesticides that may be used with more confidence in their safety, Sumitomo Chemical is conEcotoxicological Risk Assessment of Pesticides in Terrestrial Ecosystems Sumitomo Chemical Co., Ltd. Environmental Health Science Laboratory Toru UTSUMI* Mitsugu MIYAMOTO Toshiyuki KATAGI