Exposure factors resources: contrasting EPA's Exposure Factors Handbook with international sources

Efforts to compile and standardize human exposure factors have resulted in the development of a variety of resources available to the scientific community. For example, the US Environmental Protection Agency (EPA) developed the Exposure Factors Handbook and Child-specific Exposure Factors Handbook to promote consistency among its various exposure-assessment activities. The US EPA handbooks are compilations of human exposure factors data, including anthropometric and sociocultural data (e.g., body weights, skin-surface areas, and life expectancy), behavioral data (e.g., non-dietary ingestion rates, activity/time use patterns, and consumer product use), factors that may be influenced by the physiological needs of the body, metabolic activity, and health and weight status (e.g., water and food intake, and inhalation rates), and other factors (e.g., building characteristics). Other countries have engaged in similar efforts to compile and standardize exposure factors for use in exposure and risk assessments. For example, the ExpoFacts database contains data for 30 European Union countries. Australia, Canada, Japan, Korea, and Taiwan have developed, or are developing, documents that provide exposure factors data relevant to their populations. The purpose of this paper is to provide an overview of some of the available exposure factors resources; to explore some of the similarities and differences between the US EPA Exposure Factors Handbook and selected other international resources, and to highlight data gaps and present some considerations for promoting consistency among these resources.