ABSTRACT
The term biomarker has been gaining acceptance in recent years, albeit with some inconsistency in de–nition. Here we de–ne a biomarker as any biological response to an environmental chemical at the individual level or below demonstrating a departure from the normal status. Thus biochemical, physiological, histological, morphological, and behavioral measurements may be considered biomarkers. Table 10.1 illustrates examples of biomarkers at different organizational levels. Biological responses at higher organizational levels-population, community, and ecosystem-are considered bioindicators. Notwithstanding the importance of changes at these higher levels (Chapters 12, 15, and 16), they are too general to be considered speci–c biomarkers.
