Chemical activity as an integrating concept in environmental assessment and management of contaminants.

It is suggested that chemical activity in environmental media can serve as an integrating concept for holistic evaluations of contaminants, including their fate and effects. In support of this assertion, information underlying the thermodynamic principles and the relationships between monitored and modeled concentrations and activities are presented. The toxicological significance of activity is discussed, with emphasis on substances that exert baseline narcosis. Illustrations are given of the application of activity using models and monitoring data for chemical risk assessment and management. It is argued that the proximity of prevailing multimedia environmental activities to activities causing toxic effects is a particularly insightful metric of environmental contamination for both narcotics and reactive toxic substances.