THE USE OF HEMATOLOGICAL EFFECTS IN THE DEVELOPMENT OF MINIMAL RISK LEVELS

The Agency for Toxic Substances and Disease Registry (ATSDR) derives m inimal risk levels (MRLs) to assist in evaluating risk of adverse heal th effects in individuals exposed to hazardous substances. MRLs are de rived from published values identifying no-observed-adverse-effect lev els (NOAELs) or lowest-observed-adverse-effect levels (LOAELs) in anim al or human studies. The most sensitive end points are used. To date, 4 inhalation MRLs and 13 oral MRLs have been derived from hematologica l end points for 12 substances. This paper provides a brief overview o f the hematological system, examples of hematological end points, and the MRL for substances with hematological end points.