### UNITED STATES ENVIRONM ENTAL PROTECTION AGENCY WASHINGTON, D. C

. 20460

MEMORANDUM Date: September 4, 2014 

### OFFICE OF CHEMICAL S AFETY A ND POLLUTION 

### PREVENTION

SUBJECT: MCP A. Response to Comments Received Regarding Seeping Document in Support of Registration Review

PC Code: 03050 I, 030502, 030516, 030564 Decision No.: 491963 Petition No.: Not Applicable Risk Assessment Type: Single Chemical TXR No.: Not Applicable MRID No.: None
FROM : Alexandra LaMay, Biolo ist Danette Drew, Chemist Linda Taylor, Toxico logist Risk Assessment Branch DP Barcode: 0420782 Registration No.: Not Applicable Regulatory Action: Registration Review Case No.: NA CAS No.: 94-74-6 40 CFR: § 180 .339

THRU: Health Effects Division (7509P) Office of Pesticide Programs Michael Metzger, Chief , \ 

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# lf---'J Health Effects Division (7509P) Office of Pesticide Programs 

### TO: Khue Nguyen Pesticide Re-evaluation Division (7508P) Office of Pesticide Programs
Attached is the Health Effects Division's (HED) response to comments received regarding the human health seeping document for MCPA to support the registration rev iew process.

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### Task Force Comments Regarding the Human Health Risk Assessment Scoping Document: Task Force Comment: We believe that thi s product is erroneously classified and should be corrected to PC Code 030564, the 2-ethylhexyl ester ofMCPA to simpli fy the Registration Review Case. 

### HED Response : This comment will be addressed by PRD.



### Task Force Comment: The listing of uses shown is acceptable if intended as a high level summary, however, we observe that many additional sites are listed in the MCPA RED Appendix A, Use Patterns Subject to Reregistration for MCPA. 

### HED Response: Any use sites registered at the time ofthe registration review risk assessment will be considered. No changes to the scoping document are required at this time.



### Task Force Comment: Guidance is requested from EPA to define the locati on and distribution offield trials. Data may be available to address some or all ofthe zones. 

### HED Response: The EPA review ofthe 2007 magnitude of the residue on pea study (MRID 47253101; D346715, 4/8/08, T. Goodlow, MCPA. Magnitude of Residue and Storage Stability Study on Peas) concluded the following: In order to support all uses on peas , five additional field trials including MCPA and its metabolite 2

-HMCPA are required. These trials should be conducted in growing regions 1 or 2 (1 trial) and region 5 ( 4 trials) in accordance with OPPTS Guideline 860.1500. Concurrent storage stability data should be submitted with the additional field trials and conducted within the storage interval demonstrated in the storage stability study

.


### Task Force Comment: In brief, MCPA is registered for use on alfalfa, barley, clover, flax , oats, pasture and rangeland grass, peas, rye, triticale, wheat, grass grown for seed, turf, lawns, golf courses and rights-of-way. It should be noted that for all these applications there are limited if any re-entry activities post application. Active ingredient-specific TTR data exist for turf uses. Since MCPA applications to all crops are made early in the growth cycle when plant height is**~<** 6 inches and surface areas ofleaves are small , the results from the existing TTR evaluations that mimic these conditions should be applicable for evaluation of dislodgeable foliar residues. If , after considering these points, EPA still believes a DFR study is necessary, Agency input will be required with regard to appropriate sampling techniques since a leaf punch system typically used for DFR studies will no t be applicable. Data from the Agricultural Re-entry Task Force may also provide evidence that MCPA crops are not appropriate or well-suited to conduct ofDFR studies

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### HED Response: Since the scoping document was completed in February 2014, the DFR data requirement screen has been updated to require DFR data when the occupational postapplication MOEs are less than 2 times the LOC (<200) ; previously DFR data were required when MOEs were less t han 4 times the LOC (<400). Due to this change, DFR data are no longer required for MCPA. The updated data requirement determination is below. Page 2 of 5In accordance with 40CFR158, DFR data are required for all occupational (e.g., crop, nursery, greenhouse use sites) or residential (e.g., ornamental and vegetable gardens , pick your own farms , retail tree farms) uses that could result in post-application exposure to foliage. In the absence of chemical-specific DFR data, EPA uses default values. The 2012 Standard Operating Procedures for Residential Pesticide Exposure Assessment includes an analysis of a number of DFR studies , which resulted in the selection of a revised default values for the fraction ofthe application rate available for transfer after a foliar application (FAR)

. These values are based on an analysis of 19 DFR studies. Since that time, the Agricultural Re-entry Task Force has submitted information (MRID 49299201) that corrects an application rate error made in the original submission of"ARF039- Determination ofDermal and Inhalation Exposure to Reentry Workers During Chrysanthemum Pinching in a Greenhouse" (EPA MRID 45344501). As a result, th e range ofF AR values was revised from 2%

- 89% to 2%

- 47%. In the data, a large range oftransferability is observed and this variability can potentially be attributable to many factors such as active ingredient; formulation; field conditions in the studies; weather conditions (e.g., humidity); or many other difficult to quantify factors. Although witnessed across multiple chemicals, this range in FAR values is not expected when considering DFR data for a single chemical. At this time, the ARTF submission did not alter the selection of25% as the reasonable, high-end default value. Because DFR data are not available for MCPA, EPA is using the default value of25%. Although there may be a small degree ofuncertain ty in the use ofthe default DFR value for MCPA (i.e., there is a small chance that the FAR value may exceed the applicable defaul t value), it is likely that the health-protective aspects ofEPA's occupational post-application assessment methodology will more than compensate for this potential uncertainty. For example, when assessing residential and occupational post-application exposure to gardens and ornamentals, EPA assumes the following: exposures occur to zero-day (i.e., day of application) residues every day ofthe assessed exposure duration (i.e

. , EPA assumes that no dissipation or degradation occurs, it doesn't rain, etc); individuals perform the same postapplication activities performed in the transfer coefficient study day after day (e.g., weeding, harvesting, pruning, etc .) ; and individuals engage in these post-application activities for a high

end amount oftime every day (represented by data reflecting time spent gardening based on survey data). Given the conservatisms discussed above and the potential compounding nature ofthese conservatisms, EPA is able to rely upon the calculated exposure estimates with confidence that exposure is not being underestimated. Since the highest estimated occupationa l post-application exposure using default DFR values for MCPA is minimal in comparison to the level of concern (i.e., the calculated MOE is greater than 2 times higher than the level of concern, MOEs 

### > 200 compared to the LOC of 1 00); EPA is waiving the 40CFR DFR data requirement. In this instance, it is unlikely that chemical-specific DFR data would be needed to further refine exposure assessments or would add appreciably to our overall understanding ofthe availability of dislodgeable foliar pesticide residues for MCPA. Task Force Comment: The Task Force's understanding ofthe "direct application" to livestock wording is that it applies to livestock in a rangeland situation where MCPA herbicide applications may potentially be made when livestock cannot be excluded from the treatment area Page 3 of 5with certainty. Rangeland is often not managed with fences so it may be unenforceable to require that li vestock be excluded for MCPA application. We believe this is in part why EPA requires a 0 day pre-grazing interval for rangeland. Compared to application rates, the dairy cow feeding study on MCPA included much exaggerated oral doses to provide a considerable margin of exposure for any theoretical residues that might arise from dermal exposure.
HED Response: HED agrees with the assertions ofthe Task Force regarding the potential for livestock exposures in trea tment areas and that the oral doses from the feeding studies are protective of any dermal exposures. The deletion of the term "direct application' f rom the tolerance expression is a matter ofpolicy on how tolerances are worded and does not affect the tolerance levels oflivestock commodities and does not impact the MCPA risk assessment. (For the current policy on tolerance expression see USEPA, S. Knizner, 5/27/09, Interim Guidance on Tolerance Expressions). Task Force Comment: The LD50 cited is unreasonably low given the limited toxicity ofMCPA and the Toxicity Category III assigned to this LD50 value. It very likely should be 2.2 g/kg. HED response: The Task Force is correct. The acute oral LD50 value for MCPA EHE should read 2.2 g/kg. Task Force Comment: The MRID number listed (MRID 48606401) is the number assigned to the 28-day inhalation study. The correct MRID number for the DNT study is 4806030 1

. HED response: The Task Force is correct. The MCPA DNT MRID is 48060301.
Task Force Comments Regarding Tier I Review of Human Incidents :

Task Force Comment: The PC code should be li sted as 030564, however it is not unreasonable to include 030563 in a retrospective search for MCPA incidents. HED Response: This comment will be considered during registration review. No changes to the incident review are required at this time. Task Force Comment: Comments are inhibited by the lack of information provided regarding the referenced incidents. It appears that the product invo lved was distributed by a major consumer marketer as a hose-end sprayer package. The number ofincidents may have been driven by sizeable sales. HED Response: This comment will be considered during registration review. No changes to the incident review are required at this time. Task Force Comment: The listing ofuses shown is acceptable if intended as a high level summary, however, we observe that many additional sites are listed in the MCPA RED Appendix A, Use Pat terns Subject to Reregistration for MCPA.
Page 4 of 5HED Response: Any use sites registered at the time of the registration review risk assessment will be considered. No changes to the scoping document are required at this time.

Task Force Comment: The MCPA Task Force Three is unsure why the SENSOR-Pesticides data base that notes MCPP in air sampling monitor data would be included in the Tier I Review of Human Incidents for MCP A. HED Response : EPA confirms the S ENSOR-Pesticides MCPA query includes the statement. EPA has put in an inquiry with NIOSH and Washington State Department of Health to determine if this is an error.
Comments from California Water Boards Regarding MCPA

CA Water Board Comment: In order to prevent water quality impairments caused by MCPA we are requesting the following action in registration review: Consider the cumulative risk of additive toxicities between MCPA and other phenoxy herbicides. HED Response : EPA has not made a determination that the phenoxy herbicides have a common mode of toxic action. EPA will take this comment into consideration during registration review .

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