Pure and Applied Chemistry

Abstract: Regulatory authorities and other scientific organizations around the world have developed hazard/risk assessment practices that involve the derivation of numerical values said to represent "acceptable" or "safe" levels of human exposure to individual chemical substances. Human data would be preferable for this purpose since interspecies extrapolation would not be necessary. In most cases, however, these data are not available or are inadequate for this purpose. Therefore, results from studies conducted in non-human mammalian species are used as the principal or sole basis for hazard/risk assessment. Existing risk assessment frameworks developed for the evaluation of endpoints of toxicity for chemical substances are sufficiently flexible to incorporate knowledge concerning the mode(s)/mechanism(s) of action by which these endpoints occur, including those involving disturbance of normal endocrine status ("endocrine disruption"). Background on nomenclature, traditional practices using non-human animal models, and the nature and adequacy of data sets for deriving acceptable human exposures for chemicals, including endocrine active substances, are described, as is how/why the existing frameworks are adequate for the purpose of deriving numerical values for endocrine active substances. Projections on how assessment practices for these substances may evolve further in the future also are offered.