Occupational Pesticide Post-application Exposure Data

This webpage provides technical information on data used to assess occupational post-application exposure to pesticides. It is intended for anyone conducting occupational pesticide post-application exposure assessments.

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Over the past 25 years, the Agency has been actively engaged in the refinement of its methodologies and development of data for assessing exposures that may occur while performing job-related activities in areas that have been treated with pesticides. These are generally referred to as occupational “post-application” exposures, and include activities such as:

  • Hand-harvesting fruits and vegetables,
  • Thinning orchard crops,
  • Scouting fields for pests,
  • Working in greenhouses, and
  • Golf course maintenance.

To estimate exposures for individuals conducting these kinds of activities, the Agency uses a “transfer coefficient” – an exposure metric that relates total exposure for a particular hand labor task to the amount of residues on the treated surface and time.

Transfer coefficients are calculated based on actual exposure monitoring of individuals involved in a specific hand labor task. The results obtained from exposure monitoring are used to determine total dermal exposure and normalized per hour worked. A ratio is then derived between this value and a representative concentration of the transferable surface residue in the area where the worker conducted the activity – known as either dislodgeable foliar residue or turf transferable residue depending on where the activity occurred. Initial literature discussed using transfer coefficients generically for other chemicals where the same hand labor task may occur (Popendorf et al, 1980 & 1982, Zweig et al 1984 & 1985). Using estimates for crop- and chemical-specific residues and an estimate of exposure duration, transfer coefficients from available exposure studies could be used generically for other chemicals.

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Data Call-In and Formation of the ARTF

Throughout the 1980s and 1990s, the Agency used the limited number of transfer coefficients established in early published literature (e.g., fruit tree harvesting and strawberry harvesting) to assess exposure and risk for all crops and activities. Recognizing the initial screening level approach was insufficient to represent the diversity of crops and tasks, the Agency, under Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authority, required additional data that would allow for more refined post-application exposure assessments (see 40 CFR §158 for more information on pesticide data requirements). As a result, EPA issued a Data-Call-In (DCI) in 1995 to all pesticide registrants who had agricultural crop registrations.

In order to address the requirements of the DCI, the industry-based Agricultural Reentry Task Force (ARTF) Exitwas formed. Based on the information provided by ARTF and working in conjunction with the California Department of Pesticide Regulation, Canada’s Pest Management Regulatory Agency, and the U.S. Department of Agriculture – an agronomically-based, task-specific approach for assessing post-application exposure was developed.

Since its formation, the ARTF has served as the major conduit through which farmworker post-application exposure monitoring data have been generated. As a wide range of crop-specific hand labor tasks occur in production agriculture, generating data and transfer coefficients for each crop-activity combination would be prohibitively expensive and unnecessary given the reasonable similarities between crops and activities. The ARTF has conducted 47 studies, all of which have undergone appropriate ethical review according to Agency regulations regarding human exposure research. These studies provide sufficient information to satisfy the requirements of the Agency’s DCI.

Each study or a group of studies is used as a “cluster” to represent naturally similar crop-activity types. The “clustering” approach taken by ARTF, developed in consultation with the regulatory agencies, is based on monitoring of selected activities used to represent similar types of activities as defined by the crop, the ergonomics of the post-application activity, and the potential for contact with pesticide residues.

This method of grouping similar crops and activities is intended to capture the universe of hand labor tasks and assign each with an appropriate transfer coefficient dataset. For example, it is believed that harvesting oranges and apples have similar exposure potential because both crops are grown similarly in orchards making the physical act of harvesting and potential for contact with foliar residues essentially the same. Development of ARTF data and its subsequent use in this “clustering” fashion was favorably reviewed at a 2008 FIFRA SAP.

Agency use of the ARTF data is more completely described in an internal guidance document, referred to as “Science Advisory Council for Exposure (ExpoSAC) Policy 3 – Revised January 2017". Additionally, the Agency uses the Occupational Pesticide Re-entry Exposure Calculator – Revised January 2017 (XLSX)(1 pg, 2 MB) , which incorporates the information from ExpoSAC Policy 3, to estimate exposure/risk and restricted entry intervals (REIs) for field workers.

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Use of ARTF Data and Data Compensation

The ARTF is a FIFRA task force whose data are subject to the protections established in FIFRA, as a DCI was issued specifically for these data. Companies that do not belong to the task force who rely on data generated by the consortium to support a registration of a pesticide product will be required to comply with the data protection provisions of FIFRA and the Agency’s implementing regulations. Pesticide registrants interested in conducting and submitting their own post-application exposure monitoring studies for the purposes of supporting registrations still have that option.

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Incorporation of These Data in New Registrations

Many of the Agency’s existing pesticide registration decision relied on previous versions of “ExpoSAC Policy 3” to assess occupational post-application pesticide exposures. The Agency has a registration review process in which pesticides with existing registrations are reviewed every 15 years to account for any relevant exposure or toxicity information that was unavailable during previous reviews. Thus, the Agency anticipates that this updated version incorporating all available ARTF data will be used in the registration review process in most cases. It may be used in a shorter time frame, however, for other types of pesticide registration actions such as submissions of new pesticide products.

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Using the Full Distribution of Exposure Data and/or “High-End” Estimates

One of the advantages of ARTF data is the capability to analyze the data with more proper statistical procedures, including distributional analysis to evaluate the full range of exposure. Currently, the Agency plans to continue to use point-estimates from the new data deterministically in our standard exposure assessments, which evaluate short-term (up to 30 days), intermediate-term (up to 6 months), and long-term (greater than 6 months) durations as well as lifetime exposures for potentially carcinogenic chemicals. For these exposure assessments, the Agency believes arithmetic mean exposures are appropriate. However, with the additional capability to examine “high-end” exposures the Agency plans, in coordination with staff toxicologists, to develop guidance on assessing acute worker exposure and risk. Once developed, "ExpoSAC Policy 3"will be updated to include appropriate values for such assessments.

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  • Popendorf, W (1980) Exploring Citrus Harvesters’ Exposure To Pesticide Contaminated Foliar Dust, Am. Industr. Hygiene Assoc. J. 41:652-659.
  • Popendorf, W.J. and J.T. Leffingwell (1982) Regulating OP Pesticide Residues For Farmworker Protection, Residue Reviews 82: 125-201.U.S. EPA (1984). Pesticide Assessment Guidelines, Subdivision K – Exposure: Reentry Protection [NTIS Document Number PB85-120962]
  • Zweig, G., Gao, R.-Y., Witt, J.M., Popendorf, W. and Bogen. K. (1984). Dermal exposure to carbaryl by strawberry harvesters. Journal of Agricultural and Food Chemistry 32:1232-1236.
  • Zweig, G., Leffingwell, J.T. and Popendorf, W. (1985). The relationship between dermal pesticide exposure by fruit harvesters and dislodgeable foliar residues. Journal of Environmental Science and Health B20:27-59.

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