The National Exposure Research Laboratory's consolidated human activity database

EPA's National Exposure Research Laboratory (NERL) has combined data from 1 2 U.S. studies related to human activities into one comprehensive data syst em that can be accessed vis the Internet. The data system is called the Con solidated Human Activity Database (CHAD) and is available at http://www.epa .gov/nerl/. CHAD contains 22,968 person days of activity and is designed to assist exposure assessors and modelers in constructing population "cohorts " of people with specified characteristics that are suitable for subsequent analysis or modeling. This paper describes the studies comprising CHAD and the various intellectual foundations that underlay the gathering of human activity pattern data. Next, it provides a brief overview of the Internet v ersion of CHAD, and discusses how the program was formulated. Emphasis is p laced on how activity-specific energy expenditure estimates were developed. Finally, the paper recommends steps that should be taken to improve the co llection of activity data that would improve energy expenditure estimates a nd related information needed for physiologically based exposure-dose model ing efforts.