Exposures in Aquatic Ecosystems: The Weak Link in Risk Assessments - A Critical Perspective

Abstract

The foundation of assessing risk for both humans and wildlife is understanding the connection between exposure to stressors and the resulting adverse effects on life. Humans and wildlife are surrounded by a plethora of stressors in human-dominated ecosystems. Most of these stressors do not pose a threat because the exposures to adverse effect levels do not occur or occur only briefly. While the practice of risk assessment has advanced significantly in the past three decades, it still has a number of shortcomings related to our inability to characterize exposures. Widely accepted traditional monitoring and assessment methods continue to be used, which focus on measuring chemicals in water and occasionally sediments or tissues at a small number of sites, then draw conclusions on risk to biota assuming exposures are constant. Spatial and temporal variation are a dominant component of aquatic ecosystems for stressors and biological receptors. The practicality associated with characterizing these exposures and receptor movements must and can be effectively addressed to provide decision-makers with scientifically-based evidence of exposure. More accurate and cost-effective options are described for future improvements in risk assessments.