Introduction

Concern over toxicity resulting from prolonged exposure to low concentrations of toxicants was raised over 3 decades ago in Rachel Carson’s Silent Spring (1962). Presented were graphic descriptions of reproductive failure in birds, gonadal dysfunction in mammals, and cancer in humans in support of the contention that environmental pollutants were disrupting life processes at all levels of ecological organization. Over the past 3 decades, significant effort has been expended towards the identification and characterization of the toxicity of environmental pollutants. Several pieces of environmental legislation have been enacted that require characterization of both the acute and chronic toxicity of potential environmental contaminants (Foster, 1985) to species representing various levels of organization and trophic status. More recently, concern has been raised as to whether current testing protocols are adequate for the detection of toxicity associated with alterations in endocrine function (Ankley et al., 1997).