To calculate the dose received by a person from exposure to a contaminant, CalTOX uses a set of exposure factors. These factors define frequency of contact with different media (e.g., proportion of time spent indoors vs. outdoors), rate of contaminant intake (e.g., breathing rate), and other critical parameters for estimating dose (e.g., body weight).
The exposure factors used in CalTOX are based on factors adopted by the U.S. Environmental Protection Agency and by the California Department of Toxic Substances Control. The algorithms used to estimate exposures via different pathways have been reviewed extensively as a result of their use in regulatory risk assessments of hazardous waste sites and are consistent with current scientific literature and the U.S. EPA's new Exposure Factors Handbook.
REFERENCES
CalEPA, Department of Toxic Substances Control. Guidance for Site
Characterization and Multimedia Risk Assessment for Hazardous Substances
Release Sites, Volume 2. Chapter 2: Documentation of Assumptions Used in the Decision to Include and Exclude Exposure Pathways. A report prepared for the State of California, Department of Toxic Substances Control, Lawrence Livermore National Laboratory, UCRL-CR-103462. Livermore, CA.
CalEPA, Department of Toxic Substances Control. Guidance for Site
Characterization and Multimedia Risk Assessment for Hazardous Substances
Release Sites, Volume 2. Chapter 3: Guidelines for the Documentation of
Methodologies, Justification, Input, Assumptions, Limitations, and Output for Exposure Models. A report prepared for the State of California, Department of Toxic Substances Control, by Lawrence Livermore National Laboratory, UCRL-CR-103460. Livermore, CA.
EPA. Guidelines for Exposure Assessment. Federal Register 57(104): 22888-22938. May 29, 1992.
EPA, Office of Emergency and Remedial Response. Risk Assessment
Guidance for Superfund Volume I Human Health Evaluation Manual (Part A). EPA/540/1-89/002. Washington, DC. 1989.
EPA, Office of Research and Development. Exposure Factors Handbook (Final) Volumes I, II, III. PB98-124217. National Technical Information Service, Springfield, VA. 1998.
http://www.epa.gov/ncea/exposfac.htm
