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Research Abstract
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Significant Research Findings:
Minnesota Children's Pesticide Exposure Study (MCPES)
Scientific Problem Biological monitoring is often completed as part of exposure or health
and Policy Issues surveys. These results may be used to represent aggregate exposure,
which refers to the total exposure of humans to a single chemical through
all relevant pathways and routes. The interpretation of these
measurements requires information about the when, how, and for how
long the exposures occurred; and how quickly the chemical is absorbed
into and removed from the body. In addition, since biological fluids
such as blood or urine are integrators of exposures from all routes,
biological monitoring alone does not allow researchers or policy
makers to understand which route(s) or sources contributed to exposure.
Biological monitoring is most useful when combined with
corresponding human activity, environmental concentration and source
information so that the causes of high exposures can be identified and
prevented.
Research Approach In the Minnesota study, morning urine samples were collected from a
sample of children and analyzed for selected pesticide metabolites. The
population was limited to households with children, ages 3-12 years, in
urban and non-urban areas in Minnesota. Selected households included
more homes which reported frequent use of pesticides for insect control.
Pharmacokinetic (PK) models can predict the internal doses of
chemicals via ingestion, inhalation, and dermal contact. An "inverse"
PK model was used to estimate absorbed dose based on the amount of a
metabolite in the urine. Since exposures from different routes may lead
to the same dose, questionnaire and environmental monitoring data were
used to help solve the "inverse" PK models and predict the chlorpyrifos
dose and the types of exposures that may account for this.
The major metabolite of chlorpyrifos, a commonly used insecticide, was
present in 98% of the participating children's urine samples. Its
concentrations were higher in urban than in non-urban children, and
were about twice as high as those measured for adults in previous
studies. The "inverse" PK model predicted the dose resulting both from
specific pesticide exposure events and from average low-level
exposures. This dose was similar to what has been estimated for
Results and
Implications
National Exposure Research Laboratory — October 2001
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children following indoor insecticide treatments. It was lower than
previously reported exposure measurements made in adults who were
actively moving on freshly treated grass. This model may prove to be a
useful method of "disaggregating" exposure estimates based on
biological monitoring and limited survey data in future exposure studies.
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
effects data, risk assessment methods and models for children, and
control technologies needed to comply with the requirements of
FQPA"), annual performance measure (APM) 148 ("Report on
aggregate exposure of children in Minnesota to pesticides, identifying
which pathways contribute most to exposure"). Although this work
directly supports a Goal 3 APM, the results also will be valuable to
reduce uncertainties in exposure assessment under Goal 8.
The Minnesota Children's Pesticide Exposure Study was conducted in
collaboration with the Research Triangle Institute (RTI) and
Environmental and Occupational Health Sciences Institute (EOHSI), the
Minnesota Department of Health, and the University of Minnesota. This
research has been published in the following manuscripts:
Rigas, M.L., Okino, M.S., Quackenboss, J.J. "Use of a Pharmacokinetic Model to
Assess Chlorpyrifos Exposure and Dose in Children, Based on Urinary
Biomarker Measurements." Toxicological Sciences 61:374-381, 2001.
Adgate, J.L., Barr, D.B., Clayton, C.A., Eberly, L.E., Freeman, N.C.G., Lioy, P.J.,
Needham, L.L., Pellizzari, E.D., Quackenboss, J.J., Roy, A., Sexton, K.
"Measurement of Children's Exposure to Pesticides: Analysis of Urinary
Metabolite Levels in a Probability-Based Sample." Environ Health Perspect
2001; 109:583-590.
The design of the Minnesota study is described in:
Quackenboss, J.J., Pellizzari, E.D., Shubat, P., Whitmore, R.W., Adgate, J.L.,
Thomas, K.W., Freeman, N.C., Stroebel, C., Lioy, P.J., Clayton, A.C., Sexton,
K. "Design strategy for assessing multi-pathway exposure for children: the
Minnesota Children's Pesticide Exposure Study (MNCPES)." J Expo Anal
Environ Epidemiol 10:145-158 (2000).
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
National Exposure Research Laboratory — October 2001
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Contacts for Questions and inquiries on NERL's research to analyze the results of the
Additional NHEXAS and Minnesota Children's Pesticide Exposure Studies can be
Information 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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