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Fungicide Exposure Assessment Among Apple and Peach Farmers in the Agricultural Health Study

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Pesticides, Occupational Exposure

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Trial Information

Fungicide Exposure Assessment Among Apple and Peach Farmers in the Agricultural Health Study

This protocol describes an exposure assessment study of farmers in North Carolina and Iowa
who personally apply the fungicides captan, thiophanate-methyl, and benomyl to apple and
peach orchards. The exposure assessment will include environmental measurements as well as
biological monitoring data. The biomonitoring data will be based on 24-hour urinary
metabolites of the three fungicides selected for study. The study is being done in
collaboration with the Agricultural Health Study (AHS), a large prospective health study of
licensed private (farmer) and commercial applicators, and the spouses of private
applicators. The AHS is sponsored by the National Cancer Institute, the National Institute
of Environmental Health Sciences and the Environmental Protection Agency. The study
described here will be conducted by the National Institute of Occupational Safety and

Retinal degeneration among applicators in the AHS has been associated with cumulative days
of use of five fungicides, including captan and benomyl, which are or have been heavily used
in orchards. Minimal monitoring data are available on fungicide exposures among orchard
applicators in the U.S. Agent-specific exposure classification in the AHS is based
primarily on questionnaire data, supplemented by exposure monitoring data from non-cohort
studies in the literature. An algorithm has been developed by AHS to estimate an
individual's cumulative exposure using information on duration, frequency and intensity of
exposure from questionnaires. The intensity piece of this algorithm identifies factors that
either increase or decrease exposure and a "weight" is assigned to each factor to reflect
the relative impact of that factor on exposure. Exposure data are need to validate these
algorithms, to identify major exposure determinants, and to evaluate the appropriateness of
the assigned weights.

Fungicides are applied at regular intervals throughout the spring and summer in orchards.
Captan is a frequently applied fungicide that will serve as the primary marker for fungicide
exposures in orchards. Participants from the AHS will be selected based on planned use of
captan. A benzimidazole fungicide, such as thiophanate-methyl or benomyl, is often applied
with captan and exposure to thiophanate-methyl and benomyl will also be monitored.
Applicator exposure will be measured using both environmental (air, dermal patch, hand) and
biological monitoring methods. Captan is metabolized to tetrahydrophthalimide, which is
excreted into the urine. Thiophanate-methyl an benomyl share a common metabolite, methyl
(5-hydroxy-1H-benzimidazol-2-yl)-carbamate, which is also excreted into the urine. Dupont
is voluntarily withdrawing its benomyl product from the market as of December 31, 2001;
however, existing supplies of benomyl may be used in 2002. Due to this "carryover" use of
benomyl and the presence of a metabolite in the urine common to thiophanate-methyl, it is
prudent to monitor benomyl exposure among participating applicators. A repeated measures
design has been proposed to address the likelihood of high within-worker variability for
exposure measures.

In summary, the objectives of this study are 1) to measure actual exposures to the target
fungicides using both environmental and biological measures of exposure, 2) to identify and
quantify major determinants of exposure, 3) to describe within- and between-worker exposure
variability, and 4) to evaluate, to the extent possible, agreement between exposure
estimates computed using the AHS exposure algorithms and exposure estimates based on actual

Inclusion Criteria


Participants will be recruited from a sub-sample of the AHS cohort.

To be eligible for this study, AHS participants must:

1. Currently grow apples or peaches and,

2. Plan to personally apply captan during the spring/summer growing season.

Type of Study:


Study Design:


Principal Investigator

Alice Sigurdson, M.D.

Investigator Role:

Principal Investigator

Investigator Affiliation:

National Cancer Institute (NCI)


United States: Federal Government

Study ID:




Start Date:

November 2001

Completion Date:

May 2013

Related Keywords:

  • Pesticides
  • Occupational Exposure
  • Biological Monitoring
  • Exposure Determinants
  • Exposure Validation
  • Occupational Exposure
  • Pesticides
  • Agriculture



National Institute for Occupational Safety and Health Atlanta, Georgia