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


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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


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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


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(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


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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.


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