Document ID: EPA-HQ-OPP-2009-0841-0040
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2020-09-02T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460
                                                                      OFFICE OF
                                                            CHEMICAL SAFETY AND
\* MERGEFORMAT
                                                           POLLUTION PREVENTION

MEMORANDUM

DATE:	June 17, 2020

SUBJECT:	Response to Public Comments on the Fenbutatin-Oxide Draft Risk Assessment for Registration Review.

PC Code:   104601
DP Barcode: D456088
Decision No:  559170
Petition No.: NA
Registration No.: NA
Regulatory Action:  Registration Review
Risk Assessment Type: NA
Case No.: NA
TXR No.:  NA
MRID No.:  NA
CAS No.: 13356-08-6
40 CFR:  §180.362

FROM:	Amelework Habtemichael, Chemist/Risk Assessor
      Monica Hawkins, Ph.D., M.P.H., Environmental Health Scientist		
		Yung Yang, Toxicologist  
	Risk Assessment Branch VI
	Health Effects Division (HED) (7509P)

THROUGH:	Julie L. Van Alstine, Branch Chief  
	Risk Assessment Branch VI
	Health Effects Division (7509P)
		
TO:	Lauren Weissenborn, Chemical Review Manager
	Melanie Biscoe, Team Leader
	Cathryn Britton, Chief
	Risk Management and Implementation Branch V
	Pesticide Re-evaluation Division (7508P)

SUMMARY

The EPA received comments on the fenbutatin-oxide draft risk assessment for registration review (A. Habtemichael, 6/27/2019, D412713) from the United States Department of Agriculture (USDA) and National Agricultural Aviation Association (NAAA).  In this memo, EPA addresses their comments and provides detailed responses to their specific comments below.

RESPONSE TO COMMENTS

Comments from The National Agricultural Aviation Association (NAAA), November 29, 2019 (Docket ID: EPA-HQ-OPP-2009-0841-0033):

NAAA Comment

NAAA is concerned that the Tier 1 level is being used in the AgDRIFT drift models for the
risk assessments of Fenbutatin-oxide. The assumptions made in the Tier 1 model do not
accurately reflect how modern agricultural aircraft are setup to apply pesticides. 

EPA Response

HED appreciates the information provided by NAAA on standard practices used by aerial applicators, along with the published articles that NAAA cited, to support their comments/recommendations.  The AgDRIFT(TM) model, a modified version of the Agricultural DISPersal (AGDISP(TM)) model, was developed as a collaborative effort between EPA, the USDA Forest Service, and the Spray Drift Task Force.  The model is used to estimate downwind deposition of spray drift from aerial, ground and airblast applications.  NAAA is correct in noting that at Tier 1, EPA relies on conservative assumptions which are intended to be protective, i.e., representative of worst-case scenarios.  While applicator standard practice may include more conservative practices in terms of spray droplet sizes, swath off-sets, and applications during atmospheric inversions, the survey data provided by NAAA indicate that those measures are not ubiquitously practiced; therefore, it would be inappropriate for HED to utilize less conservative assumptions when modeling spray drift.  However, based on the information provided by NAAA, it is clear that the organization and its affiliates are attempting to promote methods to reduce spray drift, and risk managers can consider these efforts along with the other reference materials provided by NAAA. The concerns raised by NAAA are consistent with those expressed by USDA regarding potential restrictions on droplet size leading to increases in application rate to retain the same level of efficacy given the need to ensure that foliar surfaces are properly treated.  HED will consider the information provided by NAAA in future risk assessments; however, risk assessments will continue to rely on conservative assumptions to ensure that such assessments are protective for a broad range of application practices.

NAAA Comment

NAAA questions whether the mixing loading risks for the aerial application of the WSP
formulation to orchards, vineyards, strawberries, and eggplants would realistically be of
concern. NAAA asserts that it is erroneous to assume that simply applying to more acres somehow results in a level of concern compared to applying to fewer acres. NAAA feels that if PPE is used, mixing and loading at higher use rates or treating more acres should not automatically be assumed to increase the exposure to a mixer/loader. NAAA states that, if simply spraying more acres does actually increase risk, it seems to question the use of PPE in the first place.

EPA Response

In determining exposure to occupational handlers HED utilizes "unit exposures" developed from available data sources for each handler "scenario" considered in the assessment that are expressed as mass of pesticide active ingredient (ai) exposure per unit mass of ai handled (e.g., ug/lb ai). Each scenario refers to a specific type of application equipment, formulation type, job function, and level of personal protective equipment (PPE). These unit exposures are then used generically, irrespective of chemical identity, to estimate exposure for each pesticide used in the scenario. 

The current recommended unit exposures for standard Agency occupational handler exposure scenarios can be found in the Occupational Pesticide Handler Unit Exposure Surrogate Reference Table  -  Revised March 2020 (PDF). These values are derived from a number of generic data sources, including Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1), the Outdoor Residential Exposure Task Force (ORETF) database, and the Agricultural Handler Exposure Task Force (AHETF) database, or other available registrant-submitted exposure monitoring studies.  Descriptions of data sources, as well as guidance on their use, can be found at the Agency website.  

Potential daily exposures for occupational handlers are calculated by multiplying the unit exposure by the maximum application rate (according to registered label(s)) and the area treated or amount handled (e.g., A/day, gal/day). For example, the same unit exposure values are used for soluble concentrate formulations for mixing/loading for applications via aerial, airblast, and/or groundboom equipment across the various use sites. As noted in the comment, the only thing that is different is the amount of acreage treated per day and/or the application use rate, which both have an impact on the estimated daily exposure for an occupational handler. You can find the occupational handler algorithms in Appendix A of the "Fenbutatin-Oxide: Occupational and Residential Exposure Assessment for Registration Review" (D451019, M. Hawkins, 6/27/2019) document which details the exposure calculations.  

As previously described, the format of "unit exposures" as a ratio between exposure and the amount of active ingredient handled assumes a proportional/linear relationship.  In order to estimate the amount of active ingredient handled for mixer/loaders, the Agency assumes mixer/loaders prepare solutions or loads with an appropriate amount of active ingredient to support a certain amount of area to be treated.  Multiplying that "area treated" assumption by the application rate yields an estimate of the amount of active ingredient handled for mixer/loaders, which is then multiplied by the "unit exposure" to generate an exposure estimate.  Therefore, the Agency appropriately assumes that exposure increases for mixer/loaders as they prepare larger solutions/loads to support larger areas to be treated. 

NAAA Comment

NAAA is unclear after reading the human health risk assessment whether the
dataset used to access the risks associated with WSP included the "work practices that the
Agency agreed were inconsistent with the use of water-soluble packaging as an engineering
control intended to reduce exposures." The risk assessment mentions the creation of best
practices for how to properly handle and use WSP, label language to instruct users on these
practices, and a new dataset that excludes monitoring results for inconsistent activities, but it is
not clear to NAAA which data was used for the current risk assessment. NAAA notes that previous paragraph in the risk assessment seems to indicate the older dataset was used for the risk assessment. If it is the older data that includes activities inconsistent with best practices, NAAA recommends redoing the analysis with the newer data since future labels will have instructions on the best practices for handling and using WSP. Furthermore, while NAAA recognizes that water soluble packets are an engineering control, NAAA wonders if EPA considered the use of PPE in these risk assessments in order to reduce the risks of concern.  

EPA Response

HED endeavors to use the most current data to assess exposure and risk for occupational pesticide handlers. The WSP data set included in the fenbutatin-oxide addendum memo is the newest data set that was used by HED.  See the Fenbutatin-Oxide.  Addendum Registration Review Human Health Risk Assessment to Support the Preliminary Interim Decision (D457731) for the updated aggregate risk indices (ARIs).   

Comments from USDA, November 21, 2019 (Docket ID: EPA-HQ-OPP-2009-0841-0032):

USDA Comment

USDA discusses how, for applications with backpacks and mechanically pressurized handguns, EPA's default assumptions on volume of spray applied per work day may be significant over-estimates of exposure relative to actual usage of fenbutatin oxide. It is USDA's understanding that the Agricultural Handlers Exposure Task Force (AHETF) completed a new survey on pesticide use of hand-held equipment in U.S. greenhouse and nursery facilities, and that this report was submitted to EPA (Thompson, 2019). USDA stated that default assumptions of 1000 gal/day of material handled for handgun application is approximately 2.5 times higher than even the 95th percentile of typical values. USDA requested that EPA account for this and other potential refinements when developing additional risk characterization and crafting a risk management plan for nursery and ornamental uses of fenbutatin oxide. 

EPA Response

Based on recent updates to the Occupational Pesticide Handler Unit Exposure Surrogate Reference Table  -  Revised in March 2020, HED completed a revised occupational handler assessment for fenbutatin-oxide for all registered uses.  See the Fenbutatin-Oxide.  Addendum Registration Review Human Health Risk Assessment to Support the Preliminary Interim Decision (D457731) for the updated aggregate risk indices (ARIs).   The "gallons handled" values for Handguns in Greenhouses was revised from 1000 to 175 gallons per day and Nurseries from 1000 to 300 gallons per day; Backpacks and Manually pressurized handwands in Greenhouses was revised from 40 gallons to 7 gallons and Nurseries was revised from 40 gallons to 15 gallons per day based on AHETF survey.

USDA Comment

For post-application risks driven by hand harvesting, particularly for crops where fenbutatin-oxide usage remains important, USDA suggested that consideration of some revisions of pre-harvest intervals may be more workable for growers than proposing extended re-entry intervals for hand-harvesting activities. USDA states that it understands that pre-harvest intervals are generally driven by dietary/tolerance/residue chemistry considerations, marginally extending PHIs could have the practical impact of reducing worker exposure to residues from hand-harvesting. USDA states that PHI extensions could also reduce confusion among users that is driven by situations where field re-entry intervals are longer than pre-harvest intervals. USDA states that PHI extensions would also obviate the need for growers to post re-entry intervals for every field and would still accomplish the same practical and directionally-correct risk-reduction goals.

EPA Response

The recommended revision of the fenbutatin-oxide restricted entry intervals (REIs) instead of extended Pre-Harvest Intervals (PHIs) are based on several considerations. First, a variety of physical, chemical, and biological factors determine the nature of pesticide residue transformation, dislodgeability, and dissipation in treated fields. These factors include volatilization or evaporation, hydrolysis, oxidation, photolysis, and biodegradation. The relative importance of these mechanisms is dependent on the pesticide's structure and other factors such as site-specific weather conditions in crop growing areas. For some pesticides, one degradation mechanism will predominate, such as hydrolysis or photolysis. For other pesticides, all of the above factors can influence their rate of dissipation and environmental transformation. Dissipation may also be influenced by leaf expansion and plant growth, particularly during the early phases of plant development. Second, EPA conducts post-application exposure and risk assessments assuming the workers are wearing "typical" work clothing  -  long-sleeved shirt, long pants, shoes and socks. Additional PPE is not considered in these assessments because, under the Worker Protection Standard for Agricultural Pesticides, post-application workers do not receive training in the correct use or maintenance of personal protective equipment that can be used to reduce pesticide exposures. Finally, for fenbutatin-oxide specifically, multiple activities across use sites (not just hand-harvesting) were identified as having post-application risk well beyond the current label-specified REI of two days, which negates the utility of using the PHI to address worker risk from field re-entry. Based on these considerations, HED identified REI extensions instead of PHI extensions as the focal point for risk managers to consider in addressing post-application worker risk.