This is the first of a three-part lecture characterizing the toxicity, bioaccumulation, and persistence properties of environmental endocrine disruptors (EEDs). The characterization is primarily from a health risk assessment perspective. Therefore, the effects and properties so characterized are mainly those pertinent to exposure and risk significance, rather than those dealing with adverse health effects, of which endocrine disruption is an important type. The lecture’s overall objective is to convey the concept that even for a short duration, exposure to a persistent bioaccumulative EED of low disruption potency could lead to a severe health outcome.

To facilitate the characterization so promised, this Part I presents an overview of the human endocrine system and the basic mechanisms of endocrine disruption. It then concludes with a literature review to ascertain the effects of endocrine disruption as a major health problem.

Part II reviews the factors fundamental to a substance’s fate and bioaccumulation in the environment. Another effort of Part II is to provide some evidence from the literature on bioaccumulation and long-range transport. These literature data are intended to support the asseveration that many endocrine disruptors are highly bioaccumulative.

Part III brings forth the main themes of this lecture. It illustrates how and why endocrine disruption is inducible from exposure to a persistent bioaccumulant, even when its disruption potency is low and the exposure duration is short. Part III further elucidates the notion that at times, even induction of this kind could end with a severe health outcome.