UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: September 4, 2014 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: MCPB. Response to Comments Received Regarding Seeping Document in 

Support of Registration Review 

PC Code: 019201,019202 

Decision No.: 491965 

Petition No.: Not Applicable 

Risk Assessment Type: Single Chemical 

TXR No.: Not Applicable 

MRID No.: None 

FROM: Alexandra LaMay, Biologist 

DP Barcode: 0420784 

Registration No.: Not Applicable 

Regulatory Action: Registration Review 

Case No.: NA 

CAS No.: 94-81-5 

40 CFR: §180.318 

Danette Drew, Chemist -:::-~-... 

THRU: 

Linda Taylor, Toxicologis 

Risk Assessment Branch VII 

Health Effects Division (7509P) 

Office of Pesticide Programs 

Michael Metzger, Chief, 

Risk Assessment Branch VII 

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 MCPB to support the registration review process. 

Page 1 of 4 
Task Force Comments Regarding MCPB Human Health Assessment Scoping Document: 

Task Force Comment: The MCPB Task Force believes the request for additional pea field trial 

data has been made without consideration of data submitted January 29, 1999 by the 

Interregional Research Project No.4 (IR4). MRID 44754101 Corley, Johannes and Kunkel, 

Daniel (1999) MCPB: Magnitude ofthe Residue on Pea, Unpublished study prepared by IR4. 

423 p. This study provides MCPB and metabolite residue data from eight residue trials 

conducted in typical pea producing areas of the US, EPA Regions 1, 5, 10, 11 and 12. Residue 

data included in this study covers Succulent Peas with Pods, Succulent Peas without Pods and 

Dried Peas. The MCPB Task Force believes the data from this report is sufficient to support the 

continued registration of MCPB on peas and reference to additional pea field trial data identified 

in multiple places is not accurate. 

HED Response: Under registration review, HED will perform a full evaluation of the January 

1999 pea field trial study (MRID 44754101; submitted in response to a September 21, 1993 

Data-Call In notice) for scientific acceptability and will determine if the study fulfills the 

outstanding MCPB data requirement for pea field trial data. A preliminary screen of the data 

indicates that the study is scientifically acceptable and appears to meet the 860. 1500 guideline 

recommendations. There is adequate method validation and concurrent storage stability data. The 

application rate and timing match the current labels for pea use. The total number of field trials 

(8) and geographical representation (Regions 1, 5, 10, 11 and 12) are adequate. Although the 860 

guideline recommends four of the field trials be done in Region 5, only two were performed in 

this region. However, since there is adequate geographical representation overall and all samples 

(except one just above LOQ) in all the field trials had nondetectable (<0.01 ppm) residues of 

MCPB and MCPA, additional field trials in this region are not needed. MRID 44754101 appears 

to fulfill the MCPB DCI requirement for pea field trial data (GDCI-0 1920 1-16904). 

Task Force Comment: Whether for a spring planted crop or a fall planted crop, weed control 

applications with MCPB are made at early stages of pea and mint growth. Post-application 

activities are not generally expected because the preplant through early postemergence period is 

the timing for application of most available herbicides rather than for hand labor activities. Also, 

herbicide applications are primarily directed to the soil or weeds rather than to the crop plant as 

might be targeted for, e.g., insecticides or fungicides. Therefore, a DFR study on MCPB does not 

appear to be indicated by cropping practices. Early reentry is covered by PPE under the WPS 

Agricultural Use Requirements. 

HED Response: The applications on the label involve foliar applications to crops (i.e., postemergent application mint and peas); therefore, post-application exposure is possible for workers 

entering treated fields. Even if only early season activities such as irrigation are assessed for 

workers in treated fields, MOEs are still less than 2X the LOC of 100. Therefore, DFR data are 

required for MCPB. 

Since the seeping document was completed in January 2014, the DFR data requirement 

screening language has been updated. See below. 

Page 2 of 4 
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%. [n 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 of 25% as the 

reasonable, high-end default value. Because DFR data are not available for MCPB, EPA is using 

the default value of 25%. Although there may be a small degree of uncertainty in the use of the 

default DFR value for MCPB (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 of time 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 

MCPB is not minimal in comparison to the level of concern (i.e., the calculated MOE is not 

greater than 2 times higher than the level of concern, MOE < 200 compared to the LOC of I 00); 

EPA is requiring the 40CFR DFR data. Therefore, EPA is requiring the 40CFR DFR data 

requirement to facilitate any necessary exposure assessments refinements and to further EPA's 

general understanding of the availability of dislodgeable foliar pesticide residues. 

Task Force Comment: Due to recent and ongoing activities, Canadian and Codex MRLs should 

be reviewed again before the conclusion of Registration Review. Harmonization and trade 

irritant considerations may be applicable. 

Page 3 of4 
HED Response: HED is not aware of any current international MRLs for MCPB but would be 

grateful for any information that the Task Force could provide on "recent and ongoing activities" 

regarding MCPB. If Codex, Canadian or Mexican MRLs are established for MCPB during the 

registration review process, the EPA will consider any harmonization issues with U.S. tolerance 

levels. 

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