The Temporal Trend of Risk Due to Pesticides Used in Japan from 1960 to 1990. M. Gamo, Dept. of Urban Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113, Japan; and J. Nakanishi, Inst. of Environmental Science and Technology, Yokohama National University, Hodogaya-ku, Yokohama 240, Japan
For the last several decades, pesticides have been used even though the risks due to their use have always been a matter of concern. Some pesticides such as DDT have undesirable properties, i.e. persistence, bioaccumulation and/or carcinogenicity, and their use has been were banned. In their place, many pesticides have been developed. In this study the total risk to humans of major pesticides used in 1960, 1970, 1980 and 1990 in Japan were evaluated. Sixty major pesticides, which accounted for 95% of the total amount of pesticides used in 1960 in Japan, 89% in 1970, 74% in 1980 and 71% in 1990, were assessed. The amounts used were estimated from amounts produced each year corrected by imported and exported amounts. The exposure level to each pesticide was calculated by applying an environmental fate model and an exposure model to the amount used. Mackay's level III fugacity model was used as environmental fate model, and an exposure model to the amount used. Mackay's level III fugacity model was used as environmental fate model, by which the concentration of pesticide in environmental media, i.e., air, soil, water and sediment, was calculated. In the exposure model, inhalation of air, consumption of water, direct contact with soil and ingestion of vegetables, meat and fish were considered as exposure routes. The risk due to individual pesticides was evaluated based on the quotient method, in which the estimated exposure level of a pesticide is divided by its ADI or LD50 for experimental animals. Then, the risks were summed for all pesticides foe each year. Most of the values of physicochemical and toxicological properties of pesticides necessary for this study were taken from compilations in the literature, and others for which no data were available were estimated using QSAR. As a result, although the total amount of pesticides used increased approximately twofold in the period from 1960 to 1990, the total exposure level to pesticides was estimated to be nearly unchanged and total risk to human was estimated to decreased to about one-half in the same period.