Practices, Needs and Methodologies for Human Exposure Assessment

The Multimedia Risk Assessment (MMRA) Project developed as a result of findings and recommendations of the Risk Assessment Advisory Committee (RAAC). This committee of scientists with expertise in risk assessment was convened to conduct external peer review of risk assessment practices in the boards, departments and offices (BDOs) comprising the California Environmental Protection Agency (Cal/EPA). The committee held its first public meeting in June 1995 and published its report, A Review of the California Environmental Protection Agency’s Risk Assessment Practices, Policies, and Guidelines, in October 1996 (RAAC, 1996).

The RAAC concluded “Cal/EPA’s risk assessment products are of good quality both from the perspective of scientific credibility and professional practice.” However, the Committee stated that “Cal/EPA does not appear to be aware of some of the leading edge modeling techniques available and some of these may be superior in performance to the models routinely used.” The Committee also noted that there were some differences in risk assessments performed by boards and departments in Cal/EPA and their counterparts at the U.S. Environmental Protection Agency (U.S. EPA).

The committee recognized the efforts of the Department of Toxic Substances Control (DTSC) to develop the multimedia approach of CalTOX, A Multimedia Total Exposure Model for Hazardous Waste Sites (DTSC, 1993). The Committee also recognized the efforts of the Air Resources Board (ARB) and the Office of Environmental Health Hazard Assessment (OEHHA) to develop the multimedia Air Toxics “Hot Spots” Program Risk Assessment Guidelines (CAPCOA Guidelines) methodology (CAPCOA ,1993).

However, it noted that “there are two processes, driven by two groups within  Cal/EPA and two different statutory authorities” with different goals to accomplish, and each focused on the fate and transport of chemicals following emission into one environmental medium: soil, in the case of  CalTOX, and air, in the case of  Air Toxics “Hot Spots” Program Risk Assessment Guidelines. Neither deals with releases into multiple environmental media. The RAAC also noted that some programs in Cal/EPA do not use multimedia fate and transport modeling or human health risk assessment.