Agricultural pesticide workers are exposed to
pesticides not only from inhalation but also through their
skin. The dermal route of exposure to chlorpyrifos, a
common agricultural pesticide, is known to contribute
substantially to workers' total exposure, according to
researchers from the Johns Hopkins Bloomberg School of
Public Health and the U.S. Environmental Protection Agency,
who analyzed agricultural test data provided by pesticide
manufacturers. The study authors report that accurate
methods for estimating dermal exposure are important
because they form the basis for assessing and protecting
worker health. The study is published in the November
online issue of Annals of Occupational Hygiene.
"Although our study's findings aren't unexpected, they
highlight the significance of dermal exposure among
pesticide workers," said Laura Geer, the study's lead
author and a doctoral student in the Bloomberg School's
Department of Environmental Health Sciences.
Geer explained that the EPA requires pesticide
manufacturers to evaluate the potential for exposure to
pesticide handlers. "Since there is a paucity of such data
in the literature, we sought to mine these data. Our study
demonstrates their utility and value to answer questions
fundamental to dermal exposure and to protecting worker
health," she said. "For example, from these data, we were
able to estimate the fraction of pesticide absorbed through
the skin based on real-world agricultural worker
monitoring."
The study authors analyzed data from five studies,
including a total of 80 workers across nine states. The
participants held a variety of pesticide-related jobs,
including preparing pesticide formulations, loading the
pesticide into application devices, applying the pesticide
and inspecting crops after application.
They found that dermal exposure represents a
substantial portion of total exposure even though exposure
levels were found below current occupational health
standards and guidelines. For nearly one-half of the
workers monitored (34 out of 77), more chlorpyrifos was
absorbed through the skin than was inhaled. The researchers
compared methods for estimating worker exposure by
comparing residues found on clothing to levels of pesticide
metabolites in urine. They observed a substantial
difference, indicating that researchers may not be able to
precisely evaluate worker exposure using these methods.
This difference in estimates makes it difficult for
researchers to reconcile exposure and dose, increasing the
uncertainty in assessing worker risk and the development of
effective protective strategies. The study authors
recommend that additional work and research be done. They
also note that their study demonstrates that the EPA's
Pesticide Registrant Database offers a valuable resource to
researchers for the purpose of improving methods for
assessing exposure and protecting worker health.
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