POPULATION-BASED EXPOSURE MEASUREMENTS IN EPA REGION-5 - A PHASE-I FIELD-STUDY IN SUPPORT OF THE NATIONAL HUMAN EXPOSURE ASSESSMENT SURVEY

The National Human Exposure Assessment Survey (NHEXAS) Phase I study i s designed to be part of the total NHEXAS framework developed from a s eries of scientific discussions and workshops conducted by the U.S. En vironmental Protection Agency (EPA) during 1992 and 1993. NHEXAS exami nes total human exposure and is structured to include: Phase I, scopin g studies; Phase II, a full national exposure survey; and Phase Ill, a series of highly focused characterization modules. Our research progr am examines the scientific issues important to Phase II, including sta tistical sampling, methods evaluation, media concentration measurement s, formulating quality assurance goals, and identification of importan t pathways leading to exposure. To determine the feasibility of NHEXAS in characterizing human exposure for a representative population, a h ypothesis-driven design is used to answer important questions about hu man exposure to specific environmental contaminants. This paper descri bes: (1) hypotheses to be tested; (2) contaminants selected for study; (3) strategies for measuring exposure; (4) study area and population; (5) population sampling design; (6) media sampling and analysis proce dures; and (7) data analysis. The contaminants of concern in this Phas e I study include selected metals and volatile organic compounds. From these classes the first-tier contaminants to be measured are lead, ar senic, benzene, chloroform, perchloroethylene, and trichloroethylene. Contaminants selected for examination may potentially be found in many media (personal-nonoccupational, personal-occupational, indoor, and o utdoor residential air; dust; potable water; food/beverages; soil; blo od; hair; and urine) and exposures may occur by multiple routes (inhal ation, ingestion, dermal). The central hypothesis of our field study i s to discover whether individual and population exposures determined b y modeled or extant data are/are not significantly different from thos e determined directly from multipathway and multimedia measurements. I n addition, there are a series of subhypotheses ranging from pollutant -specific exposure measurement and body burden hypotheses to the optim ization of exposure models. In keeping with the NHEXAS framework, a pr obability-based population sample for total exposure and the field stu dy will be conducted in counties located throughout EPA Region 5 (Minn esota, Wisconsin, Illinois, Indiana, Ohio, and Michigan). Sampling uni ts will be households and an individual residing within each household . Environmental, exposure, and biological media sample collection will be performed by this consortium. Analyses of the external media and b iological media samples will be completed by this consortium or Federa l laboratories of the Centers for Disease Control and Prevention (CDC) , Food and Drug Administration (FDA), or EPA. The protocols and analyt ical techniques selected for use represent the best available for tota l exposure assessment at this time.