Population-scale assessment endpoints in ecological risk assessment part II: selection of assessment endpoint attributes.

Because ecological services often are tied to specific species, the risk to populations is a critical endpoint and important feature of ecological risk assessments. In Part 1 of this series it was demonstrated that population scale assessment endpoints are important expressions of the valued components of ecological structures. This commentary reviews several of the characteristics of populations that can be evaluated and used in population scale risk assessments. Two attributes are evaluated as promising. The 1st attribute is the change in potential productivity of the population over a specified time period. The 2nd attribute is the change in the age structure of a population, expressed graphically or as a normalized effects vector (NEV). The NEV is a description of the change in age structure due to a toxicant or other stressor and appears to be characteristic of specific stressor effects.