Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems

With the goal of providing food for the human race as well as having a stable food supply at present and in the future, agricultural chemicals (i.e. pesticides) are being disseminated as economically effective methods for preventing reduced yields in crops due to damage by insects and weeds. The pesticides are roughly divided from their targets into insecticides which include insect growth regulators for exterminating harmful insects, fungicides for preventing and eliminating fungi such as powdery mildew affecting the growth of plants, and herbicides which include plant growth regulators for preventing weeds, and each of them has a superior efficacy for organisms that are harmful to crops. These pesticides are intentionally applied outdoors to agricultural land, so in addition to the efficacy of pesticides for various diseases and insects that damage crops (benefit), evaluations of their impact not only on the health of farmers and consumers but also wild animals (risk) are necessary in determining their usefulness as pesticides. There is a long history of safety evaluations based on various types of toxicity tests using mammals from the standpoint of assuring the health of humans, but there has been an increase in the awareness of environmental protection recently, and evaluations of the effects of pesticides on the environment, including wild animals, have become indispensable for development of new pesticides and maintaining the registration of existing chemicals already on the market. However, there is a wide variety of wild animal species to be evaluated, and just among the vertebrates alone, there are various types including mammals, birds, reptiles, amphibians and fish. In addition, the diversity of their ecology and shortage of information on life history of some species make it very difficult to evaluate the safety for individual species. Incidentally, since the pesticides that are applied to cultivated land are considered to enter the hydrosphere of the rivers and lakes adjacent to the cultivated fields with the movement of air and rain as they undergo various types of metabolism and decomposition, the evaluation of the environmental impacts of pesticides on the ecosystem of the hydrosphere is one of the most important areas in evaluations of safety. Because of the complexity in ecology of the organisms living in the aquatic ecosystem as part of the food chain, the remarkable regional characteristics in ecosystems as observed for the differences in habitat and ecosystem between the Great Lakes in the United States and Lake Biwa in Japan and, in addition, the different aquatic ecosystem to be protected depending on the culture, ideologies and values of the people in various regions, etc., it is not only difficult to make uniform assessments, but also the current situation is one in which there is a great variety in the methodology for evaluation taken by the agencies regulating pesticides Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems Sumitomo Chemical Co., Ltd. Environmental Health Science Laboratory Mitsugu MIYAMOTO Hitoshi TANAKA Toshiyuki KATAGI