Level of Detail in Ecological Risk Assessments

Ecological risk assessment (ERA) is an iterative process that can involve proceeding through several tiers of assessment prior to obtaining results with acceptable uncertainty. The first tier (e.g., screening-level risk assessment (SLRA)) is typically conservative and serves to narrow the scope of the assessment to the main issues of concern. The strategy for subsequent assessment tiers (e.g., detailed level risk assessment (DLRA)) is dependent on a number of factors and is difficult to prejudge. Consequently, while formal prescriptive guidance may be useful for the SLRA, it would probably be constraining for DLRA and reduce the effectiveness of the risk assessment process. This paper examines the level of detail required for SLRA and DLRA. Differences between the two include: type of information; levels of resources, conservatism and uncertainty; information used; range of substances of potential concern (SOPCs) and receptors considered; use of multiple lines of evidence; level of effects estimation; point versus probabilistic estimates of exposure and effects. The appropriate level of detail for both types of risk assessment is described, but not prescribed.