Protocol for the Derivation of Environmental and Human ... - CCME

Part B, Section 2
2.3 Endpoint Definition
Suter (1993) describes two basic types of endpoints used in ecological risk assessment: assessment and
measurement endpoints. Assessment endpoints are formal expressions of the environmental values to
be protected (Suter, 1989) (e.g., decline in soil arthropod abundance). Two steps are required to
properly define these endpoints in a research project:
• identifying the valued attributes of the environment considered to be at risk, and
• defining these attributes in operational terms (Suter, 1993).
Suter (1993) indicated that there is no universal set of assessment endpoints, but that there are five
criteria that any endpoint should satisfy:
• societal relevance,
• biological relevance,
• unambiguous operational definition,
• accessability to prediction and measurement, and
• susceptibility to the hazardous agent.
Examples of assessment endpoints are given in Suter (1993), who recommends that the aforementioned
criteria be seriously considered when operationally defining assessment endpoints so that ecological
effects assessment is effective and understood at the societal level.
Measurement endpoints are measurable, quantifiable responses (e.g., LC 50 ) to a chemical stressor that
is related to a valued attribute of the ecological component (Suter, 1990). These measurable responses
are usually estimated in monitoring studies of laboratory toxicity tests and are generally referred to as
indicators (Suter, 1993). Since it is often difficult to measure assessment endpoints most data are used
quantitatively or qualitatively. Assessment and measurement endpoints are seldom the same since
assessment endpoints are usually defined on a large scale (e.g., populations, ecosystems) and
measurement endpoints on an individual level. Nevertheless, measurement endpoints should be
consistent with assessment endpoints (e.g., predictions on population decline based on mortality
estimates). Examples of measurement endpoints related to assessment endpoints are given in Suter
(1993).
In terrestrial toxicity testing, most data focused on mortality (LC 50 ) as a short-term endpoint and
reproduction, growth, development, behaviour, activity, lesions, physiological changes, respiration,
nutrient cycling, contribution to decomposition, genetical adaption, and physiological acclimatization as
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