UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: September 4, 2014 

OFFICE OF 

CHEMICAL SAFETY AND 

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, Toxicologist 

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, \ J ~ () ), 1 ~ Risk Assessment Branch VII iJt{ ~aJ' ' 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 MCP A to support the registration review process. 

Page 1 of 5 
Task Force Comments Regarding the Human Health Risk Assessment Scoping Document: 

Task Force Comment: We believe that this product is erroneously classified and should be 

corrected to PC Code 030564, the 2-ethylhexyl ester of MCP A to simplify 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 MCP A. 

HED 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: Guidance is requested from EPA to define the location and distribution 

of field trials. Data may be available to address some or all of the 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 MCP A and its metabolite 2-HMCP A 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 MCP A 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 not 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. 

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 than 4 times the LOC (<400). Due to this change, DFR data are no longer required for 

MCP A. The updated data requirement determination is below. 

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In 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 of the 

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 of Dermal and Inhalation Exposure to Reentry 

Workers During Chrysanthemum Pinching in a Greenhouse" (EPA MRID 45344501). As a 

result, the range ofF AR values was revised from 2% - 89% to 2% - 4 7%. In the data, a large 

range of transferability 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 ofuncertainty in the use 

of the default DFR value for MCPA (i.e., there is a small chance that the FAR value may exceed 

the applicable default value), it is likely that the health-protective aspects of EPA'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 of the 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 highend 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 of these 

conservatisms, EPA is able to rely upon the calculated exposure estimates with confidence that 

exposure is not being underestimated. 

Since the highest estimated occupational 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 of the availability of dislodgeable foliar pesticide residues for MCP A. 

Task Force Comment: The Task Force's understanding of the "direct application" to livestock 

wording is that it applies to livestock in a rangeland situation where MCP A herbicide 

applications may potentially be made when livestock cannot be excluded from the treatment area 

Page 3 of 5 
with certainty. Rangeland is often not managed with fences so it may be unenforceable to require 

that livestock 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 MCP A 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 of the Task Force regarding the potential for 

livestock exposures in treatment areas and that the oral doses from the feeding studies are 

protective of any dermal exposures. The deletion of the term "direct application' from the 

tolerance expression is a matter of policy on how tolerances are worded and does not affect the 

tolerance levels of livestock commodities and does not impact the MCP A risk assessment. (For 

the current policy on tolerance expression see US EPA, S. Knizner, 5/27/09, Interim Guidance on 

Tolerance Expressions). 

Task Force Comment: The LD50 cited is unreasonably low given the limited toxicity of MCP A 

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 48060301. 

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 listed 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 involved was distributed by a major 

consumer marketer as a hose-end sprayer package. The number of incidents 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 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 MCP A. 

Page 4 of 5 
HED 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 SENSOR-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 MCP A 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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