Page 777 - The Toxicology of Fishes

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Ecological Risk Assessment

David R. Mount and Tala R. Henry

CONTENTS
Introduction............................................................................................................................................757
The Evolution of Environmental Toxicology and Ecological Risk Assessment.................................. 758
Ecological Risk Assessment: Definitions and Concepts.......................................................................760
Risk Assessment Paradigm ..........................................................................................................760
Hazard Identification and Problem Formulation................................................................760
Exposure Assessment or Exposure Characterization.........................................................762
Exposure–Response Assessment or Effects Characterization ...........................................762
Risk Characterization..........................................................................................................763
Risk Management ..................................................................................................................................764
Comparison of Human Health and Ecological Risk Assessment.........................................................765
Hazard Identification or Problem Formulation............................................................................766
Assessment Endpoints..................................................................................................................766
Extrapolation and Testing ............................................................................................................766
Integration of Human Health and Ecological Risk Assessment...........................................................767
Applications of Risk Assessment ..........................................................................................................767
Uncertainty in Risk Assessment............................................................................................................768
Challenges for Toxicology to Advance Ecological Risk Assessment ..................................................771
Describing Ranges of Effect Rather Than Single Thresholds ....................................................771
Interpreting Sublethal Effects ......................................................................................................771
Identifying Modes of Action Not Represented by Standard Assays ..........................................772
Better Extrapolation/Reducing Animal Usage.............................................................................772
Multiple Stressors/Nonchemical Stressors...................................................................................772
Linkage of Organismal and Suborganismal Responses
to Population and Community Response ...............................................................................772
Conclusion..............................................................................................................................................773
Acknowledgments..................................................................................................................................773
References..............................................................................................................................................773

Introduction

Ecological risk assessment has been defined as “a process that evaluates the likelihood that adverse
ecological effects may occur or are occurring as a result of exposure to one or more stressors” (USEPA,
1992). Conceptually, risk assessment is implied by Paracelsus’ observation that “only dose differentiates
a remedy from a poison.” Risk is not an inherent property of a chemical toxicant but rather the product
of its toxicity and the exposure received. Hence, the same chemical can show little risk at low exposures,
but high risk at high exposures. This basic concept is embedded in our everyday behaviors. Gasoline is
potentially very toxic to human beings, but we handle it without a thought on an almost daily basis.
Why? Because even though gasoline has high toxicity, we have decided, consciously or unconsciously,

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