Overview of the use of the U.S. EPA exposure factors handbook.

Risk assessments are important components of the decision making process. At hazardous waste sites, they are used as tools to determine appropriate cleanup levels. Therefore, it is critical that the best up-to-date methods, models, and exposure data are available to the exposure and risk assessor to realistically estimate the potential for human and ecological exposures to environmental contaminants. The EPA Exposure Factors Handbook published in 1997 is a tool available to exposure assessors which summarizes statistical data on exposure factors necessary to conduct human health exposure assessments. Since it was first published by EPA in 1989, the handbook has been the primary source of data for human exposure assessments. The purpose of this paper is to provide an overview of the handbook, its impact, applications, discussion about data gaps, and future directions.