Concepts of Thresholds in Standards Setting

Abstract

The premises on which the concept of thresholds of toxicologic response rest are presented and discussed In light of recent, seemingly conflicting evidence from nontoxicologic quarters. Review of the metabolic factors governing toxicologic response, particularly homeostasis and adaptation, makes a good case for the existence of thresholds for chemical substances generally. Possible exceptions are certain natural body metabolities and long-wave ionizing radiation. Finally, the procedures that have to be taken to modify thresholds for the development of appropriate industrial air standards are presented.