An integrated framework to identify significant human exposures (SHELs)

Typically, health risk assessment methodologies have been designed to assess risks associated with exposure to individual chemicals through one specific medium, such as air, water, or food. This is partly because classical experimental methodology is used to study pure chemicals, and partly because a majority of early promulgated environmental laws (e.g., Clean Air Act, Clean Water Act) regulated chemicals in a given matrix via a specific route. Often, however, exposures in the ambient environment are through multiple routes, multiple media and to multiple chemicals. Presented here is a multimedia framework that health risk assessors can use to identify significant human exposure levels (SHELs) on a site-specific basis. This framework is presented in the context of a decision tree that links health guidance values such as minimal risk levels (MRLs) with sites-pecific data, using a range of decision-support models. It includes a provision to estimate a level of concern by comparing the estimated total dose (exposures) with guidance values established by the Agency, by other federal organizations, and by basket-survey results. If a SHEL has been identified, a range of follow-up public health actions may be indicated (i.e., surveillance, health education, or other preventive interventions). This framework serves to (1) integrate the overall health assessment process, (2) evaluate the need for public health interventions, (3) incorporate innovative decision-support methods/models, and (4) demonstrate utility of such methods in public health practice and the pursuit of the Agencyʹs mission.