Comparison of Allowable Exposures to Pesticides in Air, Water, Soil, and Food. M. A. Kamrin, Institute for Environmental Toxicology, C-231 Holden Hall, Michigan State University, East Lansing, MI 48824
Because the management of chemical contaminants in the environment to protect human health has been based on a media-specific approach; e.g., Clean Air Act, Clean Water Act, acceptable exposure limits for various media have often been developed independently at both the Federal and State levels. The implications of the resulting media-specific regulations and policy choices for comparative risk assessment can be seen in the different exposure limits promulgated by various government bodies nationally and in the states. This will be illustrated using a set of ten pesticides for which allowable exposures in ambient air, water, soil and food have been developed or can be calculated using established procedures. Federal government limits for these pesticides have been promulgated only for drinking water and food. Permissible soil and air levels will be based on the approach taken in Michigan because this is one of the few states that has a well developed approach for establishing maximum exposure levels for these two media. For drinking water, the U.S. EPA Maximum Contaminant Level or Lifetime Health Advisory value will be used for exposure assessment; for food, U.S. EPA tolerance levels will be the source; for soil, the Michigan Environmental Response Division's soil contact values (for soil remediation) will be used; and for ambient air, the Michigan Air Quality Division's approach which may be based on the OSHA Permissible Exposure Limit, the NIOSH Recommended Exposure Level or the EPA Reference Dose or Concentration will be employed. U.S. EPA default assumptions are used in the calculations. However, in addition, more realistic values based on averages and/or actual measurements are calculated. The implications and the sources of the differences in allowable daily exposures from the different media, under the various exposure scenarios, will be explored. It will be seen that the application of different risk management approaches by a variety of government bodies has led to a greater emphasis on chemical exposures from some media than others. As a result, government agencies may devote sizable resources to decrease exposures from one media although these are much lower than exposures from other media; e.g., exposures to pesticides at waste sites compared to exposures from other sources.