Occupational Pesticide Handler Exposure Data

This web page provides technical information on the most current data used to assess exposure and risk for occupational pesticide handlers. It is intended primarily for both internal Agency technical users as well as external stakeholders conducting occupational pesticide handler exposure assessments.

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The Agency uses the term “handlers” to describe the following individuals who are involved in, and potentially can experience exposure during, the pesticide application process in agricultural and non-agricultural settings:

  • Mixer/Loaders: individuals perform tasks in preparation for an application.  For example, prior to application, mixer/loaders would mix a liquid pesticide concentrate with water and load it into the holding tank of the airplane;
  • Applicators: individuals operate application equipment during the release of a pesticide product onto its target;
  • Mixer/Loader/Applicators: individuals who perform all aspects of the pesticide application process; and,
  • Flaggers: individuals that guide aerial applicators during the release of a pesticide product onto its target.

The Agency utilizes “unit exposures” as the basis for assessing handler exposures to pesticides. Unique “unit exposure” values have been developed from available data sources for each handler “scenario” considered in our assessments, and are expressed as mass of pesticide active ingredient exposure per unit mass of active ingredient handled (e.g., µg/lb ai). A scenario refers to a specific type of application equipment, formulation type, job function, and level of personal protective equipment (PPE).  The Agency then uses these unit exposures “generically,” irrespective of chemical identity, to estimate exposure for each pesticide used in the scenario.

The "Occupational Pesticide Handler Unit Exposure Surrogate Reference Table - Revised November 2016" is a quick reference guide that presents the current recommended unit exposures for standard Agency occupational pesticide handler exposure scenarios. These values are derived from a number of sources, including the Pesticide Handler Exposure Database (PHED), the Outdoor Residential Exposure Task Force (ORETF)  the Agricultural Handler Exposure Task Force (AHETF), Exit or other available registrant-submitted exposure monitoring studies.  Occupational exposure studies are subject to ethics review pursuant to 40 CFR 26.  All data sources listed here have undergone appropriate review and are compliant with applicable ethics requirements.  For certain studies that review has included review by the Human Studies Review Board.

Until the late 1990s, recommended unit exposures were generally derived only from PHED. However, since then, both the ORETF and AHETF have produced pesticide handler exposure monitoring data that the Agency uses in place of PHED. The Agency has also recently evaluated and incorporated other available registrant-submitted occupational exposure monitoring studies. These updated values are reflected in the exposure surrogate reference table. As more reliable data become available (such as that from the AHETF and ORETF) the Agency will continue to replace existing data and update and re-post the reference table. More detailed descriptions of each data source as well as “Qs & As” related to the use of newly available AHETF and ORETF data are provided below.

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Pesticide Handler Exposure Database (PHED)

PHED has been the major source of generic unit exposures used by the Agency as the basis for its exposure assessments for conventional pesticides and some antimicrobial pesticide uses. It is a software system designed by a task force of representatives from the U.S. EPA, Health Canada, the California Department of Pesticide Regulation, and member companies of the American Crop Protection Association that consists of two parts:

  • a database of measured exposure values for workers involved in the handling of pesticides under actual field conditions and
  • a set of computer algorithms used to segment and statistically summarize the selected data.

It contains values for over 1,700 monitored individuals. Once the data for a given exposure scenario have been selected, the data are typically normalized (i.e., divided by) by the amount of pesticide handled, then adjusted by the dermal surface area for the region of the body, resulting in standard unit exposures (milligrams of exposure per pound of active ingredient handled). Following this, the data from various body parts are summarized and the distribution of exposure values for each body part (e.g., chest or upper arm) are categorized as normal, lognormal, or “other” (i.e., neither normal nor log-normal). A central tendency value (e.g., arithmetic mean for normal distributions, geometric mean for lognormal distributions, and median for “other” distributions) is selected from the distribution of the exposure values for each body part. These are then summed into a "best fit" central tendency value representing the entire body.

In order to add consistency to the risk assessment process the data within PHED were analyzed and a series of standard exposure values for the most common occupational exposure scenarios of concern were developed and compiled into a reference document known as the “PHED Surrogate Exposure Guide”. The actual PHED computer program was developed in a database language that is no longer technically supported, so the Surrogate Exposure Guide was an efficient method for providing the information contained in PHED in a readily accessible format. The exposure surrogate reference table incorporates the recommended values from the PHED Surrogate Exposure Guide, as well as updating those handler scenarios with new data.

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Agricultural Handler Exposure Task Force (AHETF)

The Agricultural Handler Exposure Task Force (AHETF) Exit is a consortium of chemical companies established in December 2001 to jointly address ongoing, product-specific Agency exposure data requirements. The AHETF is developing a compensable database of information that can be used to calculate exposure for major agricultural and non-agricultural handler scenarios. As described above, the Agency currently uses values presented in the PHED Surrogate Guide as the basis for most pesticide handler exposure assessments. However, the Agency believes that given changes in cultural production practices over time and the limitations of the data contained in PHED, it is appropriate that more current information be used for these types of assessments as they become available. These issues and others were extensively addressed at a FIFRA SAP in January 2007.

The AHETF has developed exposure study design criteria to ensure that the new database incorporates a robust statistical design and improved analytical methods, and is representative of current handling techniques. The AHETF data generally reflect individuals wearing long-sleeved shirts, long pants, shoes plus socks, and chemical-resistant gloves. Some exposure monitoring may reflect use of engineering controls such as enclosed tractor cabs or specialized types of product packaging designed to reduce exposures.

These aspects have been reviewed by the Agency’s Office of Pesticide Programs (OPP) Health Effects Division (HED) and presented to the Human Studies Review Board (HSRB) along with criteria for determining when a new AHETF exposure scenario is complete. The Agency considers the AHETF data to be the “most reliable” and will – going forward – rely on these data for routine exposure and risk assessments for pesticides whose use is consistent with the AHETF monitored exposure scenarios. Thus, as AHETF data for each pesticide handler exposure scenario becomes available, they will supersede existing data. Completed AHETF data is presented and reviewed in the form of “monograph” reports and are available upon request.

The Agency has now reviewed and accepted ten (10) completed AHETF scenarios:

  1. Open Pour Mixing and Loading Dry Flowable
  2. Open Pour Mixing and Loading Liquids
  3. Open Cab Groundboom Application
  4. Closed Cab Airblast Application
  5. Open Cab Airblast Application
  6. Closed Cockpit Aerial Application
  7. Backpack Application in Rights-of-Ways and Similar Use Sites
  8. Handgun Application in Rights-of-Ways and Similar Use Sites
  9. Open Pour Mixing and Loading Wettable Powders
  10. Mixing and Loading Water Soluble Packets

The Agency is currently reviewing AHETF data for various other scenarios, including mixing/loading pesticides in enclosed systems and applications in greenhouses and nurseries. If considered acceptable and the “most reliable” for those respective exposure scenarios, the Agency will begin to routinely utilize the data in place of existing data. Completed AHETF data is presented and reviewed in the form of “monograph” reports and are available upon request.

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Outdoor Residential Exposure Task Force (ORETF)

The Outdoor Residential Exposure Task Force (ORETF) Exitis a consortium of chemical companies that formed a joint data development task force in December 1994 in anticipation of satisfying data requirements outlined in a March 1995 Agency Data Call-In (DCI). The DCI required mixer/loader/applicator dermal and inhalation exposure data and post-application exposure data for over one hundred active ingredients. The occupational handler exposure studies conducted by the ORETF represented professional lawn care operators (LCO) and 

  • Mixer/Loader/Applicator, “Push-type” Rotary Spreader
  • Mixer/Loader/Applicator, Handgun Sprayer (liquid, water-dispersible granule, and wettable powder formulations)

These studies were Agency reviewed and have been in use, supplanting PHED data for similar handler exposure scenarios, since 2003.

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Questions and Answers

Why is the Agency using AHETF and ORETF data, as well as exposure data from other submitted studies, to assess exposure for pesticide handlers?

The Pesticide Handler Exposure Database (PHED) houses the majority of occupational pesticide handler exposure data the Agency uses in occupational handler exposure assessments. The Agency has recognized and acknowledged the limitations with the existing data. Since the late 1990s, the Agency and stakeholders have expressed a desire to augment or replace this database with one that has as its foundation a more contemporary dataset and one whose exposure monitoring followed a more robust, consistent, and statistically-driven sampling design. In January 2007, the Agency presented to a FIFRA SAP both the limitations to existing data and the proposed development of new data by an industry consortium, the Agricultural Handler Exposure Task Force (AHETF).

With joint input by Health Canada’s Pesticide Regulatory Management Authority and California’s Department of Pesticide Regulation throughout the data development processes, the Agency believes that the AHETF and ORETF data are superior, and that use of these data will result in more reliable and scientifically defensible exposure assessments. Additionally, the Agency considers exposure data submitted by registrants outside of the AHETF or ORETF, to be the most appropriate data for some scenarios and are used in a similar fashion.

Can a company rely on “old” PHED data for assessing exposure for a particular scenario if other data are available for that scenario?

No. While existing (“old”) data from PHED will continue to be used for exposure scenarios without more reliable data (e.g., AHETF or ORETF data), the Agency will use AHETF, ORETF, or other registrant-submitted data in place of the PHED when it has been reviewed and considered acceptable to use by the Agency. Pesticide registrants interested in performing exposure assessments should refer to the table posted on this web page for the most up-to-date standard unit exposures used in Agency pesticide handler exposure scenarios. Pesticide registrants also interested in conducting and submitting their own handler exposure monitoring studies for the purposes of supporting registrations still have that option.

Does a company’s reliance on AHETF, ORETF, or other submitted exposure data require compensation?

Yes. Both the AHETF and ORETF are industry consortia whose data are subject to the protections established in FIFRA. Companies that do not belong to the consortium 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. This also applies to studies individually submitted by pesticide registrants which the Agency similarly utilizes for exposure assessment purposes.

How will registration decisions incorporate new data?

Many of the Agency’s existing pesticide registration decisions relied on “old” data to assess exposure to pesticide handlers. The Agency has in place 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 AHETF, ORETF, or other submitted exposure data will be incorporated in the registration review process in most cases. New data may be incorporated in a shorter time frame, however, for other types of pesticide registration actions such as submissions of new pesticide products.

Does the Agency have plans to utilize the full distribution of exposure data and/or “high-end” estimates?

The reference table presents “arithmetic mean” values for data derived from sources other than PHED (e.g., AHETF and ORETF). One of the advantages these datasets have over PHED 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 utilize 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 the exposure surrogate reference table will be updated to include appropriate values for such assessments.

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