Practical Risk Assessment and Management Issues Arising were we to Adopt Low-Dose Linearity for all Endpoints.

The 2009 National Research Council report, Science and Decisions, proposes harmonizing dose-response approaches for cancer and non-cancer endpoints, and for non-cancer quantitative risk assessment, this would usually take the form of a low-dose linear no-threshold dose-response curve. The soundness of this recommendation has been questioned, but I focus on its consequences if adopted, many of them apparently unintended. If most endpoints for most agents are assumed to have non-zero low-dose risks, then the critical-effect concept, choosing the one endpoint on which to calculate acceptable doses, loses its basis. All regulatory decisions, since they entail substituting some exposures (and their attendant risks) for others, become risk-risk trade-off decisions, and equity questions are raised since risk transfer is inevitably involved. A valid basis for estimating low-dose linear components is not evident, and upper-bound approaches fail to be reliably public health-protective owing to the risk trade-off decisions that need to be faced.