ABSTRACT
The second approach is to compare the distributions of effects and exposure within the watershed. In this method, the results of the refined risk analysis are presented as a distribution of toxicity rather than a single point estimate. This approach uses all relevant single-species toxicity data and compares them to exposure distributions. Solomon et al. (1996) described this approach, summarized the assumptions, and provided examples. When both exposure (EEC) and effects (acute or chronic toxicity) are expressed in a probabilistic manner, decisions can be made to attempt to protect 95 percent of the species from all chronic effects. This also provides a good estimate of the maximum acceptable concentration and a target for mitigation measures.
