Depending on how species are grouped in the analysis, an ecological
risk assessment might lead to different conclusions about
risk. For example, use of a comparative risk assessment, which separates
species into groups (i.e. plants and animals), may be more
appropriate when assessing chemicals that have very high toxicity,
but only for one group of organism. Including all species in the
analysis may be more appropriate for chemicals that have more
uniform toxicity across species groups. In this paper we compare
the use of both risk assessment approaches for three different classes
of pesticide, the herbicide diuron, the fungicide chlorothalonil,
and the insecticide permethrin.