NERL/NCEA Research Abstract EPA's National Exposure Research Laboratory and the National Center for Environmental Assessment GPRA Goal 8 - Sound Science Significant Research Findings The National Human Exposure Assessment Survey (NHEXAS) Pilot Studies: Early Findings Scientific Problem and To evaluate the risks posed by chemical pollutants in the environment EPA must be Policy Issues able to estimate the number of people exposed to the pollutants as well as the magnitude and duration of the exposure. Until recently, estimates of exposure have been based on "default assumptions," such as emissions or enviromnental concentration data, rather than on actual measures of human exposure to contaminants. Without measurements of human exposure, these default assumptions are of limited value because they do not reflect actual patterns (distributions) of human exposure to chemicals in the enviromnent. Increasingly, EPA's scientific advisors are concerned about reliance on these default assumptions - particularly when evaluating the risks from exposure to enviromnental contaminants or when estimating the benefits that may be obtained from managing these risks. Addressing these concerns is a vital link in reducing the scientific uncertainty in health risk assessment and in regulatory decision making. To respond to these concerns, EPA's Office of Research and Development sponsored three related pilot studies known as National Human Exposure Assessment Survey (NHEXAS). The NHEXAS studies respond to these concerns by testing protocols for acquiring population distributions of exposure measurements and by developing exposure databases for use in exposure models, exposure assessment, and risk assessment. The NHEXAS pilot studies include projects that focus on actual measures of human exposure to enviromnental contaminants encountered in daily living in three regions of the United States. Forty-one commonly encountered enviromnental contaminants were selected for investigation in the NHEXAS projects-including pesticides, heavy metals, and volatile organic compounds. About 550 volunteer participants were randomly selected from the three regions of the country to obtain a "population-based probability sample" that would represent the distribution of exposures for the residents in each region. Scientists measured the levels of chemicals to which these participants were exposed~in the air they breathe, in the foods and beverages they consume, in the water they drink (duplicate diet), and in the soil and dust around their homes. Measurements were made also of chemicals in biological samples (including blood and urine) provided by the participants. Finally, Research Approach ------- participants completed questionnaires to help identify possible sources of exposure to chemicals and to describe their major activity patterns and the conditions of their residential environment. Scientists used the exposure measurements and questionnaire data to determine participants' pathway-specific and total exposures to the contaminants. Scientists also determined which pathways are responsible for the greatest exposures. The NHEXAS studies provide unique information on the ranges of actual exposures in the general population for use as "benchmarks" for site-specific investigations and for health risk assessments. A recently published report1 from EPA's Science Advisory Board (SAB) on the NHEXAS pilot studies confirms the value of this information. The SAB concluded that NHEXAS is an excellent project that has significant promise for improving public health in a cost-effective manner. The SAB report found NHEXAS to be outstanding in both design and implementation. When completed, the SAB believes that NHEXAS should greatly improve understanding of human exposure to the pollutants it investigated. This, in turn, will be helpful in determining the most effective strategies to reduce the public's risk to hazardous environmental chemicals. Results and During 1999, scientists completed the measurement and sample analysis phase of the Implications pilot program, permitting EPA to begin an evaluation of the NHEXAS projects and the information they obtained. An initial series of articles was published during 1999 in the Journal of Exposure Analysis and Environmental Epidemiology? Significant findings include: The NHEXAS pilot projects demonstrated the feasibility of multi-media, multi-pathway human exposure studies. The pilot projects provide protocols for sophisticated exposure measurements, exposure concentration data, activity pattern data, and population-based distributions of exposure for a variety of chemicals. These studies are able to discern even small differences in exposures in outdoor and indoor environments where adults and children live, play, attend school, and work. These studies also are able to discern sources that contribute to total exposures-or to differences in exposure across communities or regions. For example, significant differences in total exposure to arsenic were found between communities that have, or do not have, mining industries. The participants selected for the NHEXAS projects compared well with U.S. census data-for both the general population and for portions of the population (e.g., children, racial and ethnic groups, or groups defined by socioeconomic status). This confirms that population-based human exposure studies can be designed to have an important role in investigating environmental justice issues or concerns about susceptible subpopulations. NHEXAS measurement and activity pattern data are rigorous enough to support detailed evaluations of the numerous "default assumptions" that limit current risk assessments. For example, NHEXAS data indicate that infants' and children's average hand-to-mouth-contact rate is about 9.5 contacts/hour rather than the assumed rate of 1.6 contacts/hour. Since young children's exposure to metals such as lead or to pesticides is influenced significantly by hand-to-mouth-contact, more accurate information such as this can have important consequences for protecting the health of our children. A wealth of additional information is presented in the sixteen articles included in this ------- publication. leeAn SAB Advisory: the National Human Exposure Assessment Survey (NHEXAS) Pilot Studies," February 1999. U.S. EPA Science Advisory Board (EPA-SAB-IHEC-ADV-99-004). Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pages 369-529. Research Collaboration NHEXAS has been implemented with extensive research collaboration that includes and Publications scientists from EP A's Office of Research and Development, from other federal agencies, and from leading academic and research institutions. Scientists from the Food and Drug Administration and from the Centers for Disease Control and Prevention participated with EPA scientists in the analysis of samples. Scientists from the National Institute for Standards and Technology provided quality assurance support. The NHEXAS projects were funded as cooperative agreements and coordinated by EPA's Office of Research and Development: The cooperative agreement supporting the Arizona study included the University of Arizona, Battelle Memorial Institute, and the Illinois Institute of Technology. The cooperative agreement supporting the Region 5 study (states of Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin) included the Research Triangle Institute and the Environmental Occupational Health Sciences Institute. A related smaller-scale study in Region 5 focused on children's exposures to pesticides and was conducted with the participation of the Minnesota Department of Health. The cooperative agreement supporting the Maryland study included Harvard University, Emory University, Johns Hopkins University, and Westat. For information about the three NHEXAS projects described in this Research Abstract, please contact: Region 5 Studv: Edo Pellizzari, PhD Research Triangle Institute 919-541-6579 edo@rti.org Arizona Studv: Michael Lebowitz, PhD. University of Arizona 520-626-7090 lebowitz@resp-sci.arizona.edu Maryland Studv: P. Barry Ryan, PhD. Emory University 404-727-3826 ryan@fox.sph.emory.edu James Quackenboss U.S. EPA 702-798-2442 quackenboss.james@epa.gov Gary Robertson U.S. EPA 702-798-2215 robertson.gary@epa.gov Karen Hammerstrom U.S. EPA 202-564-3258 hammerstrom.karen@epa. gov The following research publications are referred to in this Research Abstract. All of these publications appeared in the Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pages 369-529. Region 5 NHEXAS Pilot Studv: Whitmore, R.W., Byron, M.Z., Clayton, C.A., Thomas K.W., ZelonH.S., Pellizzari E.D., and Quackenboss.J.J.. "Sampling Design, Response Rates and Analysis Weights for the National Human Exposure Assessment Survey (NHEXAS) in EPA Region 5" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 369-380. Clayton, C.A., Pellizzari, E.D., Whitmore, R.W. Perritt, R.L. and Quackenboss, J.J. "National Human Exposure Assessment Survey ------- (NHEXAS): Distributions and Associations of Lead, Arsenic and Volatile Organic Compounds in EPA Region 5" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 381-392. Pellizzari, E.D., Fernando, R., Cramer, G.M., Meaburn, G.M., and Bangerter, K. "Analysis of Mercury in Hair of EPA Region V Population" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 393-401. Thomas, K.W., Pellizzari, E.D., and Berry, M.R. "Population-based Dietary Intakes and Tap Water Concentrations for Selected Elements in the EPA Region V National Human Exposure Assessment Survey (NHEXAS)" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 402-413. Freeman, N.C.G., Lioy P.J., "Responses to the Region V NHEXAS Time/Activity Diary." Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 414- 426. Reed, K.J., Jimenez, M., Freeman, N.C.G., and Lioy, P. J. "Quantification of Children's Hand and Mouthing Activities Through a Videotaping Methodology" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 513- 520. Edwards,R.D., and Lioy, P.J. "The EL Sampler: A Press Sampler for the Quantitative Estimation of Dermal Exposure to Pesticides in Housedust" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 521-529. Baltimore NHEXAS Pilot Study: Scanlon, K.A., Macintosh, D.L, Hammerstrom, K.A., and Ryan, P.B."A Longitudinal Investigation of Solid-Food based Dietary Exposure to Selected Elements" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 485-493. Macintosh, D.L., Needham, L.L., Hammerstrom, K.A., and Ryan, P.B. "A Longitudinal Investigation of Selected Pesticide Metabolites in Urine" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 494-501. Echols, S.L., Macintosh, D.L., Hammerstrom, K.A. and Ryan, P.B. "Temporal Variability of Microenvironmental Time Budgets in Maryland" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 502-512. Arizona NHEXAS Pilot Study: Robertson, G.L., Lebowitz, M.D., O'Rourke, M.K.,Gordon, S., and Moschandreas, D. "The National Human Exposure Assessment Survey (NHEXAS) Study in Arizona-Introduction and Preliminary Results" Journal ------- of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 427-434. O'Rourke, M.K., Fernandez, L.M., Bittel, C.N., Sherrill J.L., Blackwell, T.S., and Robbins, D.R. "Mass Data Massage: An Automated Data Processing System Used for NHEXAS Arizona" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 471-484. O'Rourke, M.K., Rogan, S.P., Jin, S., and Robertson, G.L. "Spatial Distributions of Arsenic Exposure and Mining Communities from NHEXAS Arizona" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 446-455. Gordon, S.M., Callahan, P.J., Nishioka, M.G., Brinkman, M.C., O'Rourke, M.K., Lebowitz, M.D., and Mosschandreas, D.M. "Residential Environmental Measurements in the National Human Exposure Assessment Survey (NHEXAS) Pilot Study in Arizona: Preliminary Results for Pesticides and VOCs" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 456- 470. O'Rourke, M.K., Vande Water, P.K., Jin, S., Rogan, S.P., Weiss, A.D., Gordon, S.M., Moschandreas, D.M., and Lebowitz, M.D. "Evaluations of Primary Metals from NHEXAS Arizona: Distributions and Preliminary Exposures" Journal of Exposure Analysis and Environmental Epidemiology (Volume 9, Number 5, September / October, 1999), pp. 435-445. Future Research Interpretation and research involving data from the NHEXAS pilot study will continue for several years. During 2000, EPA will complete a strategic analysis plan to identify comprehensive priorities for the analyses of NHEXAS data. After this plan is reviewed by the SAB, it will guide further NHEXAS pilot analyses. By 2002, EPA plans to make the complete set of NHEXAS data and metadata available for public access and downloading from an EPA web site. This will stimulate human exposure research by public and academic organizations for many years. ------- |