Data base selection in toxicological risk assessment and management.

In recent years, there has been increasing awareness of the differences in maximum allowable levels developed by the various federal regulatory agencies. It has generally been presumed that the variation in levels arises from differences in risk management decisions, i.e., how the data are used. This study was undertaken to test the hypothesis that differences in choice of data to utilize also have a significant impact on interagency variation. To test this hypothesis, a comparison was made between the data bases used by the EPA Office of Drinking Water and the Occupational Safety and Health Administration in setting maximum levels for pesticides in drinking water and workplace air, respectively. The results show that the same data are only infrequently used as bases for both types of regulatory levels. The study also indicates that the differences in data selection cannot be ascribed to factors related to the applicability of different data for the two types of exposures--drinking water and workplace air. There are essentially no differences in the data with respect to route of exposure, species (laboratory animals vs humans), or length of exposure. No obvious scientific basis for the differences was found. Other possible selection factors are discussed.