Occupational Pesticide Exposure - Seed Treatment

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

On this page:

• Basics of Seed Treatment Exposure Assessment
• Seed Treatment Exposure Assessment Policies
• Seed Treatment Exposure Calculator
• Questions and Answers

Pesticides, such as fungicides, insecticides and nematicides, are applied to seeds prior to planting to protect them from diseases, insects, or other pests. Treatments are made to a variety of crop seeds from grains and oilseed crops (e.g., wheat, corn, canola, etc.), to fruits and vegetables (e.g., broccoli, melons, etc.), as well as to “seed pieces” (e.g., potatoes). Treatment of seed can occur in commercial seed treatment facilities, after which growers can purchase and plant already-treated seed. In other cases, growers may choose to treat seed on their own – known as “on-farm” seed treatment – and then plant the treated seed. Commercial seed treatment facilities are strictly dedicated to treating seed using large-scale automated machinery. Therefore, workers can treat very large amounts of seed (e.g., greater than 100,000 pounds). On-farm seed treatment is typically a more manual treatment operation and, as would be expected, growers will use different equipment and treat smaller amounts of seed (e.g., greater than 1,000 pounds).

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Basics of Seed Treatment Exposure Assessment

As part of the Agency’s pesticide registration or registration review process, a pesticide proposed or registered for use on seed is evaluated for its safety in occupational settings. Based on available data, EPA estimates exposure for a variety of seed treatment activities and tasks, using a “scenario-based” approach:

• Commercial Seed Treatment
  • Treating: performing tasks directly associated with the seed treating/coating process including loading the chemical, treating/coating the seeds with continuous flow or batch machinery, calibrating the equipment, and sampling treated seed.
  • Packaging: performing tasks associated with the packaging/storing/transporting of treated seed including bagging, tagging, stacking, forklifting, and sampling treated seed.
  • Cleaning: cleaning the interior of the treatment machinery and/or the treatment mixture containers or delivery systems.
  • Loading and Planting
• On-farm Seed Treatment, Loading and Planting: treatment prior to loading seed into planter (e.g., spraying or pouring liquids while seed is moving along auger or conveyer system or application of solids in a mixing drum) or direct application of liquid or solid product to seed already in planting equipment (e.g., in hopper boxes).

The data used to assess occupational exposures during seed treatment largely come from the Agricultural Handler Exposure Task Force (AHETF), a consortium of pesticide manufacturing companies, who, in collaboration with EPA (and other regulatory agencies), reviewed dozens of seed treatment exposure studies, and, against a set of data quality criteria, selected 17 studies representing the best available data to assess each seed treatment exposure scenario. References and descriptions of the studies are contained within the seed treatment assessment policies linked to below. EPA reviewed the AHETF submissions and agreed with the approach, though the final dataset incorporates additional standard EPA pesticide data analysis practices. Additionally, occupational exposure studies are subject to ethics review pursuant to 40 CFR 26. All seed treatment data sources have undergone appropriate review and are compliant with applicable ethics requirements.

The AHETF is an industry consortium whose data are subject to the protections established in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Companies that do not belong to the consortium whose pesticide registration relies on data generated by the consortium 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. Pesticide registrants interested in conducting and submitting their own seed treatment exposure monitoring studies for the purposes of supporting registrations still have that option.

Seed Treatment Exposure Assessment Policies

Seed treatment exposure assessments typically consist of three pieces of information (or “inputs”), whose combination results in a seed treatment worker exposure estimate:

• Application rate: the amount of active ingredient applied to the seed (e.g., milligrams of active ingredient per pound of seed), as described on the pesticide product label from the chemical company.
• Unit exposures: data-based, scenario-specific exposure estimates typically expressed as mass of pesticide active ingredient exposure per unit mass of active ingredient handled (e.g., µg/lb ai). Seed treatment scenarios were described above and refer to type of treatment (commercial or on-farm) and tasks (treating, packaging, cleaning), but also may include formulation type and level of personal protective equipment (PPE). The Agency then uses these unit exposures “generically,” irrespective of chemical identity, to estimate exposure for each scenario applicable to the proposed pesticide use.
• Amount of seed treated, amount of seed planted or time spent cleaning treatment equipment.

EPA presents this seed treatment assessment approach in two separate policy documents authored by the Agency’s Science Advisory Council for Exposure (ExpoSAC):

• Standard Operating Procedures for Seed Treatment (“ExpoSAC Policy 14”) (pdf) (1.83 MB)  - originally developed in 2003 and updated in 2022 following review and acceptance of more reliable data, this policy presents the “unit exposures” for each seed treatment scenario and the underlying information that supports them.
• Standard Values for Amount of Seed Treated and/or Planted Per Day (“ExpoSAC Policy 15”) (pdf) (1.46 MB)  - originally developed in 2004 with a major update in 2017 and minor updates in 2021 and 2022 as new seed industry survey data have become available, this policy presents amounts of seed treated and planted and the underlying information that supports the default values.

Seed Treatment Exposure Assessment Calculator

While the seed treatment policies serve as the underlying documentation and rationale for EPA’s seed treatment exposure assessment approach, the Agency has incorporated that underlying policy guidance in an easy-to-use Microsoft Excel-based calculator tool, which enables a faster and more efficient assessment process and, by standardizing the calculations, ensures that each proposed seed treatment registration is handled similarly. Additionally, by making it publicly available at the link below, all stakeholders can transparently see how seed treatment exposure assessments are conducted.

• Seed Treatment Exposure Calculator (March 2022) (xlsx) (1.06 MB)

Note: A previous version of the Seed Treatment Exposure Assessment Calculator was released in January 2022. This version corrects errors related to input values for seed count and calculations for exposures while planting treated seed. Refer to the calculator’s “Update Timeline” worksheet for more information.

Questions and Answers

• Why is the Agency updating its seed treatment exposure assessment data?
• Can a company rely on the previously used seed treatment data for assessing exposure to seed treatment workers?
• Does a company’s reliance on AHETF or other submitted exposure data require compensation?
• How will registration decisions incorporate new data?

Why is the Agency updating its seed treatment exposure assessment data?

The current version of the “Standard Operating Procedures for Seed Treatment (ExpoSAC Policy 14)” dates to 2003, relying on studies conducted from 1986-2001. Since then, the Agency and stakeholders have expressed a desire to augment or replace this database with one that has as its foundation a more contemporary and robust dataset that lends itself to more sophisticated data analysis. Following curation of available seed treatment exposure monitoring studies, the AHETF submitted data packages in 2008 and 2013, consisting of studies conducted in the United States, Canada, and Europe from 1999-2010. Additionally, the Agency identified an additional seed treatment exposure monitoring study submitted in 2014 that the Agency incorporated with the AHETF submission. The Agency completed its review of all the submitted seed treatment exposure studies in 2022. The Agency believes that use of the updated dataset will result in more reliable and scientifically defensible exposure assessments.

Can a company rely on the previously used seed treatment data for assessing exposure to seed treatment workers?

No. The previously used seed treatment data was reviewed for continued incorporation in “ExpoSAC Policy 14”. However, the previously used data was considered inferior in comparison to the newer data and not included in the update to “ExpoSAC Policy 14”. Pesticide registrants interested in performing exposure assessments should refer to the materials posted on this web page for the most up-to-date standard exposure calculation inputs used in Agency seed treatment 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. Should that occur, the Agency will review and consider the study in the context of all of the new data in “ExpoSAC Policy 14” to determine what is the most reliable for risk assessment purposes.

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

Yes. The AHETF is an industry group 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 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 the previously used data to assess exposure for seed treatment workers. 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 the data in the updated seed treatment exposure policy will be incorporated throughout the registration review process. However, for any new seed treatment uses or proposed changes to existing seed treatment uses, the new data will be used beginning in January 2022.