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STRATEGIC PLAN FOR THE ANALYSIS OF THE NATIONAL HUMAN EXPOSURE ASSESSMENT SURVEY (NHEXAS) PILOT STUDY DATA
Citation:
Berry Jr., M R., J A. Graham, S C. Hern, A H. Ozkaynak, D A. Pahl, J J. Quackenboss, K Hammerstrom, K W. Leovic, G L. Robertson, L S. Sheldon, AND W C. Steen. STRATEGIC PLAN FOR THE ANALYSIS OF THE NATIONAL HUMAN EXPOSURE ASSESSMENT SURVEY (NHEXAS) PILOT STUDY DATA. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-00/049, 2000.
Impact/Purpose:
The NHEXAS analysis projects being conducted by NERL address the following scientific issues/questions:
- Do exposure distributions vary by demographic group?
- What is the impact of censoring (BDL) on multimedia distributions and associations?
- Which questionnaire/diary items are most useful in explaining variability or identifying "high exposure" groups?
- How do exposure classifications and measurements compare in their ability to explain variability in exposures and biomarkers?
- Can changes in exposures over time be explained by dietary and questionnaire/activity information?
- How well do NHEXAS findings compare with existing models/assessments (e.g., NATA)?
Description:
The Office of Research and Development (ORD) of the U.S. Environmental Protection Agency (EPA) initiated the National Human Exposure Assessment Survey (NHEXAS) in the early 1990's. It was a population-based pilot study of the exposure of over 500 people in three areas of the U.S. to metals, pesticides, volatile organic compounds, and other toxic chemicals. Measurements were made of the air people breathed, the foods and beverages they consumed, and the soil and dust in/near their home. Chemicals in their blood and urine were measured. The participants also completed questionnaires to help identify possible sources of exposures and to characterize activities that might contribute to exposure. To this date, NHEXAS remains the largest multimedia, multipathway, multichemical study of its kind. Key goals included evaluating the feasibility of conducting such a large study, documenting the population distribution of exposure to the chemicals examined, understanding the factors that contribute to high exposures, and improving the accuracy of exposure models.
Such a study produces a multitude of data that must be thoughtfully analyzed to realize its full potential. EPA's Science Advisory Board (SAB) recommended that EPA develop a strategy to analyze the data to ensure the optimal use of the data (EPA-SAB-IHEC-ADV-99-004, www.epa.gov/sab). Therefore, ORD developed this Strategic Plan. ORD began with a workshop at which about 70 scientific and policy experts from ORD, EPA program offices, EPA regions, other federal agencies, state health agencies, academia, and private institutions offered their suggestions on the most useful analyses of the NHEXAS pilot data. ORD used their thoughtful contributions as the basis to begin development of the Strategic Plan. The draft Plan was reviewed by the SAB (EPA-SAB-IHE C-00-018, www.epa.gov/sab). and made available to all EPA program offices and the public. This document has been revised based upon those recommendations.
The Strategic Plan describes projects in six topic areas: descriptive statistics; predictors of exposure and dose; spatial and temporal variability; aggregate exposure, pathway analysis, and cumulative risk; evaluation/refinement of current exposure models and assessments; and designing exposure studies. Criteria, founded on both the near- and long-term value to EPA, were established for ranking projects within each of these topic areas. The text describes how the criteria were applied to each project. The projects are described in the appendix. This prioritization will be used as a guide for ORD to implement the analyses. To expand the opportunities for all interested persons to get involved, the NHEXAS information is being prepared for entry into a publically available database, with appropriate metadata, in late 2001.
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.