Ecological Risk Assessment
An ecological risk assessment is an approach at understanding environmental
problems that uses a fundamental research approach. The goal is
to evaluate actual and predicted effects of contaminants on animal
and plant populations and their habitats or communities. In ecological
risk assessment the impact of contaminants on humans and domestic
animals is not considered. The phases of an ecological risk assessment
are: problem formulation, analysis, and risk
characterization. The analysis phase includes development of
an exposure assessment and development of an ecological effects
Problem Formulation, also known
as Response Assessment, begins with the recognition that
there is something wrong in the environment. Some evidence that
the quality of life or ecological health is "not what it should
be" is noted, such as when recreational fishers note that the
number of fish caught is declining. This response leads to a review
of existing data about the affected site. It identifies the characteristics
of the contaminant, the ecosystem at risk, and the effects to the
ecosystem. During this phase particular parts (types of plants or
animals) of the ecosystem are identified for analysis and the measurements
(expected response) are established.
The Analysis Phase includes an
exposure assessment and an ecological effects assessment.
An exposure assessment identifies and quantifies stressors
that are causing the problem by examining physical and chemical
measurements and observing biotic indices (key species that indicate
the health of a particular ecosystem). Human activities that might
affect the environment are also considered. When the stressor is
a contaminant, the movement of the contaminant through the environment
helps identify the receptors (species) that are exposed and the
concentrations of exposure. The susceptibility of a receptor to
a contaminant is determined by: properties of the contaminant, the
route of exposure into the organism (absorption, ingestion, inhalation)
and the behavior and patterns of the receptor.
The ecological effects assessment links
the concentrations of contaminants to adverse effects in receptors.
This toxicity testing is sometimes known as the "dose-response"
curve. It is a measure of the amount of the contaminant and the
degree of effect. Field studies can provide evidence of the link
between these two factors. Toxicity tests can evaluate the effects
of the contamination on the survival, growth and reproduction of
Risk characterization compares the results of the exposure
assessment with the results of the ecological effects assessment.
The conclusions lead to a numeric probability of harm. The severity
is described along with the degree of uncertainty of these conclusions.
The risk is described numerically and descriptively.
For the other risk-related pages, please see:
- Steps of Assessment. This page describes
detailed descriptions of the steps in risk assessment, with emphasis
on human health risk assessment.
- Risk Assessment Standards This
page provides a discussion on standards for risk assessment based
on the American Society for Testing and Materials.
- Risk Management This page provides
information about plans for managing and/or preventing risk.
- Risk Communication This page provides
information about communicating with communities facing contaminated