Regulatory Proposal PRO2014-02, Updated Agricultural Transfer Coefficients for Assessing Occupational Postapplication Exposure to Pesticides

(PDF Version - 93 K)

Pest Management Regulatory Agency
16 September 2014
ISSN: 1925-122X (PDF version)
Catalogue number: H113-8/2014-2E-PDF (PDF version)

Table of Contents

• 1.0 Summary
• 2.0 Purpose
• 3.0 Data Access
• 4.0 Background
• 5.0 PMRA Agricultural Transfer Coefficients
• References

1.0 Summary

Transfer coefficients (TCs) are used by Health Canada's Pest Management Regulatory Agency (PMRA) when calculating postapplication exposure to agricultural workers for human health risk assessments. The United States Environmental Protection Agency (USEPA) recently developed a database of TCs based on data presented by the Agricultural Re-entry Task Force (ARTF) to the United States' Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel in 2008. The PMRA has similarly updated the Canadian agricultural TCs based on the ARTF data. The updated agricultural TC table is available from the PMRA upon request.

These values may be updated on an on-going basis, as additional information is submitted to the PMRA.

2.0 Purpose

The purpose of this document is to provide an update to stakeholders on the TCs used by the PMRA when calculating postapplication exposure to agricultural workers.

The PMRA is also soliciting comments on the following specific questions on the agricultural TC table:

• Does handline irrigation (in other words, movement of irrigation pipes) occur with the crops identified?
• Are there any crops or activities missing? If so, please describe the crops and activities, including the typical crop height and foliage density at the time these activities occur.

The PMRA will accept written comments from the public on the PMRA agricultural TCs up to 45 days after publication of this document. Send your written comments by e-mail, fax or regular mail to Publications.

3.0 Data Access

The TCs discussed in this document are based on proprietary data submitted to the PMRA by the ARTF, which is a joint data development task force made up of pesticide registrants.

For new active ingredients or use expansions, ARTF data can only be used for products for which the registrant is a member of the ARTF or has access to the data. 'Registrant' refers to the registrant of the end-use product and/or the registrant of the technical grade active ingredient from which the end-use product is formulated. If neither the technical registrant nor the end-use product registrant are members of this Task Force, then non-proprietary TCs will be used in the agricultural postapplication exposure assessment (USEPA, 1998), although there are limitations with this data, as discussed below in Section 4.0. Alternatively, registrants can submit equivalent data to develop their own TC.

For re-evaluations of older active ingredients, ARTF data can be used for all products. If a registrant of the technical grade active ingredient from which the registered end-use products are formulated is not a member of the Task Force or does not have access to the data, then the ARTF data would be considered 'compensable'.

For more information on PMRA's data protection policies, refer to:

• Discussion Document DIS2012-01, Reliance on Proprietary Data for the Purpose of Re-evaluation and Special Review,
• Regulatory Directive DIR2010-04, Guidelines for Reliance on Proprietary Data Under the Pest Control Products Regulations,
• Regulatory Directive DIR2008-01, Registering a New Source of Technical Grade Active Ingredient Under the Protection of Proprietary Interests in Pesticide Data Policy, and
• Regulatory Directive DIR2007-03, Protection of Proprietary Interests in Pesticide Data in Canada.

4.0 Background

Under the Pest Control Products Act, the PMRA has the responsibility to protect the health of Canadians from unacceptable risks associated with pesticide use. In order to assess potential risks of pesticide use to the health of Canadians, the Agency must be able to estimate their potential exposure to pesticides and any pesticide transformation products that might be of toxicological concern. Occupational exposure assessments must be comprehensive and include potential pesticide exposure by all routes (dermal, inhalation). Estimating potential exposure to workers entering an area that was treated with pesticides is an important part of occupational exposure assessments.

Agricultural postapplication exposure assessments estimate potential exposure to pesticide residues when workers enter a treated area to perform certain activities. Residues that are on plant foliage and are available for transfer are called dislodgeable foliar residues (DFR). Residues that are on the surface of turf and are available for transfer are called turf transferrable residues (TTR).

A TC is an empirical measure of residue transferability from the foliage of plants or turf onto a worker's skin or clothing through contact. They are determined from worker exposure studies (typically passive dosimetry studies), and concurrent DFR or TTR studies. Conceptually, a TC may be thought of as a 'contact factor' determining a worker's exposure to DFR or TTR depending on what activity they are doing, the length of the workday, and how much residue is available for contact and transfer. Mathematically, this is expressed as follows.

The early work performed in establishing TCs demonstrated that postapplication exposure was primarily a function of the degree of body immersion in treated foliage and that it could be used as a generic tool for estimating exposures to workers based on a chemical-specific DFR dissipation curve. Regulatory experience in the use of TCs has demonstrated this to be valid for conventional pesticides whose physical and chemical properties fall within a similar range, and where dislodgeable foliar residues are neither very low nor very high. For most conventional pesticides, TCs can be used generically between different active ingredients; however, DFR and TTR data are chemical-specific. This process is considered a reasonable method for assessing exposure while saving the time and resources associated with conducting passive dosimetry or biological monitoring exposure studies for all proposed pesticide registrations and registration reviews, including the multitude of scenarios and uses therein.

TCs are used by PMRA and other regulatory agencies to estimate postapplication exposure. Historically, PMRA used a non-proprietary database of TCs (USEPA, 1998) for agricultural risk assessments. However, there are limitations with this database as the values were not quantitatively derived based on data, rather they were determined by pesticide exposure assessors based on professional judgement.

In October 1995, the USEPA issued a data call-in notice to all pesticide registrants requiring data on dislodgeable foliar residues and dermal TCs for virtually all pesticides applied to agricultural crops. In anticipation of the data call-in, the ARTF was formed by a number of pesticide registrants.

The approach taken by ARTF to address these data requirements, developed in consultation with the regulatory agencies, was based on the monitoring of selected activities that are used to represent similar types of activities as defined by the crop, the ergonomics of the postapplication activity, and the potential for contact with pesticide residues. 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. Due to these similarities it would then be expected that the TC for each activity would be similar since it is a measure of the potential contact with pesticide residues.

During the data development, a major undertaking of the regulatory agencies and the ARTF was to identify all activities which occur in agriculture that are necessary for the production of a crop. Aspects of this process involved distinguishing between those hand labour activities that have routine, substantive exposures associated with them and those activities which have a negligible exposure potential. Grower and expert surveys conducted by ARTF in the United States and Canada, consultation with those involved in agriculture, as well as information from crop profiles and agronomic texts were used to identify specific activities that occur in agriculture. The conclusions drawn based on this information were correlated with other independent sources, such as the National Agricultural Workers Survey by the United States Department of Labor. Based on the above information, a list of all possible agricultural activities totalling approximately 4500 crop-activity combinations was produced. These were then grouped into clusters of naturally similar crop-activity types.

The ARTF developed a database of modern worker exposure studies and concurrent DFR or TTR studies to calculate TCs, which are conducted according to current guidelines and are reflective of current agricultural practices. These studies were reviewed for use in regulatory agricultural risk assessments by the PMRA in cooperation with the USEPA and the California Department of Pesticide Regulation. All three agencies supported the use of the ARTF studies as the basis for revised agricultural TC values.

These data and a general approach to TCs were presented to the United States' FIFRA Scientific Advisory Panel in December 2008 (USEPA, 2008, 2009). The presented approach was generally accepted by the USEPA, California Department of Pesticide Regulation and Health Canada's PMRA. Based on the FIFRA Scientific Advisory Panel review and subsequent discussions, the USEPA developed a database of agricultural TCs. The TCs discussed in this document are similar to those recently published by the USEPA (2012) and reflect the ARTF TCs used by Health Canada for the regulation of pesticides.

5.0 PMRA Agricultural Transfer Coefficients

A summary of the PMRA TC clusters applied in the PMRA agricultural TC table is provided in Table 1. Most of the clusters are similar to those presented by the ARTF to the FIFRA Scientific Advisory Panel (USEPA, 2008); however, some were modified by the Agencies. Those clusters that are different than those proposed by the ARTF and were developed by the USEPA and adopted by PMRA are identified with an "(EPA)" notation, while those clusters that are unique to PMRA are identified with a "(PMRA)." Unique clusters were developed when there were differences in acceptance of individual studies and clustering rationales between PMRA, EPA and/or what was proposed by the ARTF.

The PMRA's agricultural TC table is available upon request.

References

Published

• Brouwer, R., Brouwer, D.H., Tigssen, S., and van Hemmen, J.J. 1992. Pesticides in the Cultivation of Carnations in Greenhouses: Part II- Relationship Between Foliar Residues and Exposures. Am. Ind. Assoc. J. 53(9): 582-587.
• Schneider, F., Hernandez, B., and Benson, C. 2002. Pesticide Exposure of Workers in Greenhouses. Health and Safety Report HS-1835. California Environmental Protection Agency. November 19, 2002.
• Schipper, H.J., Brouwer, D.H., and van Hemmen, J.J. 1998. Exposure to Pesticides During Re-entry Activities in Greenhouses. Field Study in Cucumber Crop. Oct.6, 1998. INO Nutrition and Food Research Institute, Netherlands Organization for Applied Scientific Research.
• USEPA. 2012. Science Advisory Council for Exposure (ExpoSAC). Policy 3. Agricultural Transfer Coefficients. Revised March, 2012. Available: http://www.epa.gov/pesticides/science/exposac_policy3.pdf
• USEPA. 2009. Transmittal of Meeting Minutes of the FIFRA Scientific Advisory Panel Meeting Held Dec 2-5, 2008 on the Scientific Issues Associated with Worker Re-entry Exposure Assessment. February 19, 2009.
• USEPA. 2008. FIFRA Scientific Advisory Panel (SAP): Scientific Issues Associated with Worker Re-entry Exposure Assessment. December 2 - 5, 2008. Documents available: http://www.epa.gov/scipoly/sap/meetings/2008/120208_mtg.htm
• USEPA. 2001. Recommended Revisions to the Standard Operating Procedures (SOP's) for Residential Exposure Assessments. HED Policy Number 12. February 22, 2001.
• USEPA. 1998. Science Advisory Council for Exposure. Policy 003. Agricultural Default Transfer Coefficients. May 7, 1998.