United States Environmental Protection Agency Office of Research and Development
National Exposure Research Laboratory
Research Abstract
Government Performance Results Act Goal: Safe Food
Significant Research Findings:
National Human Exposure Assessment Survey (NHEXAS) and
Minnesota Children's Pesticide Exposure Studies
Scientific Problem Recent regulations, notably the Food Quality Protection Act (FQPA) of
and Policy Issues 1996, require consideration of aggregate human exposure to toxic
chemicals. Aggregate exposure refers to the total exposure of humans to
single chemicals through all relevant pathways and routes. The current
use of default assumptions and approaches introduces uncertainties into
aggregate exposure estimates. Individual-level data on concentrations
and activities, and on resulting exposures and doses, are needed to help
evaluate and reduce these uncertainties. Information on the actual
ranges of pesticide exposure and dose, both for the general population
and for potentially sensitive sub-populations, is needed to determine
whether these exceed levels of concern for health effects. The National
Human Exposure Assessment Survey (NHEXAS) and the Minnesota
Children's Pesticide Exposure Study provide real-world data on
individual exposures and activities to help reduce reliance on default
assumptions and to develop and evaluate multimedia, multipathway
models of pesticide exposures.
Research Approach The NHEXAS studies measured human exposures to high-risk target
chemicals including pesticides. To accomplish this, about 500
volunteer participants were randomly selected from three areas of the
country: the state of Arizona, the greater Baltimore, Maryland area, and
the states in EPA Region 5 (Illinois, Indiana, Michigan, Minnesota,
Ohio, and Wisconsin). Pesticide exposures for about 100 children
between the ages of three and 13 were studied in Minnesota. These
studies measured both people's direct exposures to environmental
pollutants and indirect biological indicators of exposure, "biomarkers,"
in their blood or urine. The data from these studies are being analyzed
to describe distributions of pesticide exposures and differences related
to household and individual characteristics and activities, to evaluate
changes in dietary exposures and pesticide-related activities over time,
and to identify effective approaches to studying children's exposures.
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Results and Distributions of estimated pesticide exposures and sub-population
Implications differences have been developed and characterized for the Arizona
study. Estimates of both the middle and high-end of the distribution,
which were adjusted to account for the complex sampling designs used
in this study, differed by more than 30% from unadjusted estimates.
Pesticide exposures were greater for those living in households with
more carpeting, preparing or using pesticides in their homes, or having
higher household incomes. In the Maryland study, gender, age group,
and racial/ethnic group were related to the frequency of contact with
soil, grass, and carpeting. These results suggest that demographic and
household characteristics might be useful in categorizing exposures and
identifying exposure reduction strategies.
The Maryland study also found evidence of substantial changes in
dietary exposures to pesticides over a one-year period. Pesticides were
more frequently detected in food samples in spring and summer months
than in winter months. Changes in activities related to skin contact with
soil and grass were also observed; these occurred nearly twice as often
in spring and summer compared with winter months. Dermal contact
and pesticide usage activities reported for a short time period, such as a
day or a week as is the case for most exposure or activity studies, may
not accurately represent longer term activities. These results have
implications regarding the use of one-time measurements to estimate or
classify long-term (chronic) exposures.
The Minnesota Children's pesticide exposure study evaluated the
feasibility of measuring pesticide exposures in a sample of children.
Practical ways for dealing with some of the methodological and
technical problems involved in studying children's exposures were
identified, including: the important role that a local agency (Department
of Health) played both in conducting initial interviews and in helping to
ensure credibility and earn the trust of study participants; the flexibility
needed in scheduling and in allowing participants options in providing
some samples (with additional incentives for those samples involving
more effort); and the need to keep household visits short through careful
planning, staff training and practice, and automating sample tracking
systems.
The results of this project address Government Performance and Results
Act (GPRA) Goal #3 (Safe Food), Subobjective 3.2.4 (By 2005,
provide problem-driven research results to support the new FQPA
regulatory standard of "reasonable certainty of no harm" for pesticides
used on food). The results of this project address GPRA annual
performance goal (APG) 13 ("In 2001, develop pesticides exposure and
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effects data, risk assessment methods and models for children, and
control technologies needed to comply with the requirements of
FQPA"), annual performance measure (APM) 218 ("NHEXAS:
Evaluate available measurement data on aggregate human pesticide
exposure in the NHEXAS probability sample of people in 3 areas of the
U.S."). Specifically, this research will contribute to Goal 3 by
providing real-world exposure concentration and exposure factor data
on children's non-occupational exposure to pesticides that can be used
for the exposure assessments required to implement FQPA. Although
this work directly supports a Goal 3 APM, the results also will be
valuable to reduce uncertainties in exposure assessment under Goal #8
(Sound Science, Improved Understanding of Environmental Risks, and
Greater Innovation to Address Environmental Problems).
The NHEXAS analysis projects were conducted under Contracts
between EPA's National Exposure Research Laboratory and Emory
University, Research Triangle Institute, and the University of Arizona.
The Minnesota Department of Health and the University of Minnesota
participated in the Minnesota Children's Pesticide exposure study.
This research has been published in the following manuscripts:
Adgate, J.L., Clayton, C.A., Quackenboss, J.J., Thomas, K.W., Whitmore, R.W.,
Pellizzari, E.D., Lioy, P.J., Shubat, P., Stroebel, C., Freeman, N.C., Sexton, K.
"Measurement of multi-pollutant and multi-pathway exposures in a
probability-based sample of children: practical strategies for effective field
studies." J Expo Anal Environ Epidemiol 10:650-61, (2000).
Echols, S.L., Macintosh, D.L., Ryan, P.B. "Temporal Patterns of Activities
Potentially Related to Pesticide Exposure." Revised and re-submitted to J
Expo Anal Environ Epidemiol, (2001).
Macintosh, D.L., Kabiru, C.W., Ryan, P.B. "Longitudinal investigation of dietary
exposure to selected pesticides." Environ Health Perspect 109:145-50,
(2001).
Moschandreas, D.J., Kinun, Y„ Karuchit, S., Ari, H„ Lebowitz, M.D., O'Rourke,
M.K., Gordon, S., Robertson, G. "In-residence, multiple route exposures to
chlorpyrifos and diazinon estimated by indirect method models." Atmospheric
Environment35:2201-2213, (2001).
Moschandreas, D.J., Karuchit, S., Kim, Y„ Ari, H„ Lebowitz, M.D., O' Rourke,
M.K., Gordon, S., Robertson, G. On predicting multi-route and multimedia
residential exposure to chlorpyrifos and diazinon. J Expo Anal Environ
Epidemiol 11:56-65, (2001).
Future Research Future analyses of the NHEXAS data will be based on the projects
included in the Strategic Plan for Analysis of the NHEXAS Pilot Study
(EPA 600/R-00/049), which is available at
http ://www. epa. gov/nerl/research/nhexas/ strategy. pdf
Research
Collaboration and
Publications
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Contacts for
Additional
Information
Questions and inquiries can be directed to:
James J. Quackenboss
US EPA, Office of Research and Development
National Exposure Research Laboratory
Las Vegas, NV 89193-3478
Phone: 702/798-2442
E-mail: quackenboss.iames@epa.gov
National Exposure Research Laboratory — October 2001
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