USE OF MECHANISTIC AND PHARMACOKINETIC DATA FOR RISK ASSESSMENT AT THE ATIONAL-INSTITUTE-OF-ENVIRONMENTAL-HEALTH-SCIENCES (NIEHS)

In summary, the National Institute of Environmental Health Sciences (N IEHS) and the National Toxicology Program (NTP) have been important co ntributors of data for hazard identification, including toxicological data as well as mechanistic and pharmacokinetic information. One of th e factors that limits the use of knowledge is our lack of understandin g of the animal test models currently in use. The underlying bases for regulatory controls that account for normal physiological functions a re often not well understood. As a result, toxicological data tend to be used in an empirical manner rather than a manner based on mechanist ic understanding. Continued testing of chemicals and random generation of data have their limits in improving our predictive abilities. Atte ntion must be given to prioritizing studies on the basis of critical g aps in understanding that are needed to build knowledge bases in the f uture.