CORRELATION OF STRUCTURAL CLASS WITH NO-OBSERVED-EFFECT LEVELS - A PROPOSAL FOR ESTABLISHING A THRESHOLD OF CONCERN

The relationship between chemical structure and toxicity was explored through the compilation of a large reference database consisting of ov er 600 chemical substances tested for a variety of endpoints resulting in over 2900 no-observed-effect levels (NOELs). Each substance in the database was classified into one of three structural classes using a decision tree approach. The resulting cumulative distributions of NOEL s for each of the structural classes differed significantly from one a nother, supporting the contention that chemical structure defines toxi city. The database was used to derive a threshold of acceptable human exposure for each of the structural classes that could be applied in t he absence of specific toxicity data on a substance within one of the three structural classes. The human exposure thresholds provide guidan ce on the degree of testing and evaluation required for substances tha t lack toxicity data. Copyright (C) 1996 Published by Elsevier Science Ltd