Use of mechanistic and pharmacokinetic data for risk assessment at the National Institute of Environmental Health Sciences (NIEHS).

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