### UNITED STATESENVIRONMENTAL PROTECTIONAGENCY WASHINGTON D.C., 20460

PCCodes:030501,030502,030516, 030563,030564 DP Barcode: D420780



### MEMORANDUM August 14, 2014 Subject:

To:

From:

Through: EFED Response to Public Comments on: Preliminary Problem Formulation for Environmental Fate and Ecological Risk, Endangered Species, and Drinking Water Assessments for MCPA Khue Nguyen, Chemical ReviewManager Neil Anderson, ChiefRMIB I ./ Pesticide Re-Evaluation Division (7508P) 

# '3{{'f{t'( Brian D. Kiernan, Biologist

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# ) IwonaMaher, Chemist

## ~I.JdjJ....A**(~J. ~}a,**  Environmental Risk Branch VI Environmental Fate and Effects Division (7507P) Mark Corbin, Branch Chief Environmental Risk Branch VI Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has reviewedthree comments received on the preliminaryproblem formulation (D414986; 03/05/2014) for the environmental fate and ecological risk, endangered species and drinking water assessments to be conducted as part of the registration review ofthe herbicide active ingredient MCPA and its salts and ester (PC Codes 030501, 030502, 030516, 030563 and 030564). Public comments related to the ecological risk assessment were submitted by the MCPA Task Force Three, Center for Biological Diversity, and the Central Valley Regional Water Quality Control Board (ofthe California Water Boards). Responses to the specific comments are provided in this memorandum. 

### EFED Response to Comments Submitted by MCPATaskForce Three In general, the MCPA Task Force Three provided a number ofcomments regarding corrections ofcitations (e.g. MRID 42642204 was stated to be bluegill sunfish, but is actually rainbow trout)and other errata noted (e.g. an incorrect reference to a different chemical) will be corrected, as necessary, in the registration review risk assessment. Additionally, several studies were referenced in the Problem Formulation for which MCPA Task Force Three requested EPA's data evaluations records (DER). EFED will evaluate whetherthe studies in question were included in error and will provide copies ofDERs, as appropriate, under separate cover.

MCP A TaskForce Three comment (page 6): The Registration Review case is said to include PC Code 030563, the isooctyl ester ofMCPA that is generally considered an obsolete form. Early in Reregistration (ca 1990), registrants and EPA agreed that the specific C8 alcohol that would be prepared as an ester ofMCPA would be 2-ethylhexanol rather than a mixed C8 rich isooctyl alcohol or other single C8 alcohol. Today, only one product is identified in PPIS (sic) as containing PC Code 030563. EFED response: EFED will, in collaboration with the management divisions (Registration Division and Pesticide Reevaluation Division) to determine the appropriate forms to assess at the time ofrisk assessment. MCPA TaskForce Three comment (page 6): Task Force Response: An oral acute toxicity study according to OECD 213 has been submitted to EPA (MRlD 47666601). The study was reviewed in 2009 and at that time was evaluated as "

..scientifically sound

.." but was "

...classified as Supplemental as it does not meet any current guideline requirements." A second study (MRlD 45897007) evaluating the contact and oral LD50 ofMCPA acid was conducted according to EPPO Standard PP11170(2) which is cited in the OECD 213 Guideline. EFED response: The Problem Formulationrequested·two studies to evaluate the potential for MCPA to adversely affect pollinators: an acute oral toxicity study (following OECD 213) and a larval toxicity study (following OECD 237). However, EFED policy onpollinator protection has recently been updated (Guidance for Assessing Pesticide Risks to Bees, 06.23.2014; signedby Donald Brady, Director, EFED; http:/ /www2.epa.gov/sites/production/files/2014- 06/documents/pollinator _risk_assessment _guidance_06_19_14.pdf). Thus, the required studies for all pesticides that have use patterns which can result in exposure to pollinators have been changed, and now include the following Tier 1 studies:

• Acute oral toxicity to adult honey bees • Acute oral toxicity to larval honey bees • Chronic oral toxicityto adult honey bees • Chronic oral toxicity to larval honey beesWhile the EFED Problem Formulation indicated that an acute oral study (OECD 213) was needed, provisional review ofthe study referenced above by MCPATaskForce Three (MRID 45897007) suggests that additional adult acute oral data will not be needed for the risk assessment. Although the adult chronic oral toxicity study was not specified in the Problem Formulation, this additional study should be conducted to support the MCPA risk assessment. While the PF did indicate that an acute larval toxicity study (following OECD 237) would be necessary, the release ofthe new guidance also requires a repeat-dose (chronic) larval toxicity study be submitted. The OECD has a draft guideline for a chronic larval toxicity study that may be utilized. Itis possible to conduct the repeat-dose study in such a way as to derive both an LDso (acute endpoint ofinterest) and a NOAEC (chronic endpoint ofinterest) from a single study. Ifthe chronic larval toxicity study is conducted in such a way that it derives both an LDso and NOAEC, then a separate acute larval toxicity study is not needed. Although appreciable effects are not expected, the need for higher Tier studies will be determined after review ofthese Tier 1 studies. 

### MCP A TaskForce Three comment (page 7): EPA Comment: "Since thattime theMCPA task force has voluntarily cancelledthe use on rice andsorghum in response to theRED (2004)." Task Force Response: Although the outcome is the same, it would be more accurate to state that the MCPA Task Force Three did not support uses on rice and sorghum and that all registrants voluntarily cancelled rice and sorgh1,1m uses in response to the RED (2004). 

### EFED response: This Task Force comment; and several other comments suggesting more accurate wording, are noted and will, to the extentpossible and necessary, be incorporated into the risk assessment. 

### MCP A TaskForceThree comment (page 7): EPA Comment: "MCPA is 

### usually appliedin combination with otherphenoxy class chemicals, such as 2,4-D, 2,4DB, MCPP-p, andMCPB (2004). Accordingtoproductlabels, MCPA can be appliedany time of year, but for bestefficacyapplication is 

### recommendedin earlyspringandearly fall. " TaskForce Response: MCPA is not usually applied in combination with 2,4-D and 2,4-DB. In fact, each ofthesethree products is most often used to the exclusion ofthe others. MCPA and MCPB are bothregistered for use on peas and there are occasions when a grower may use a very lowrate ofMCPA with a reduced rate ofMCPB to lower the treatment cost versus a full rate of MCPB alone. For example, an indicative productregistered in several countries contains 1part MCPAto 15 parts MCPB. Forturfand nonagricultural crop use sites, there are many EPA registered multiple active ingredient products containing combinations ofMCPA, MCPP-p, 2,4-DP-p and other non-phenoxy actives.

### EFED response: We appreciate the commentregarding the paragraph and will incorporate it, as appropriate, atthe time ofthe risk assessment. 

### MCPA TaskForceThree comment (page 8): EPA Comment: Therefore, theAgencyrequests any additionalinformation on thepresence of dioxins/furans impurities inMCPAformulatedproducts thatmaybe available basedon currently achievableLOQs. TaskForce Response: Technical phenoxy herbicide registrants have provided dioxin/furan data at intervals for several decades in response to Data Call-Ins and product chemistryrequirements applicable to impurities ofpotential toxicological concern intechnical MCPA. Relevantproduct specific studies have MRID numbers associated with the individual technical registrations. These results have demonstrated non-detectable or extremely low detections while the LOQs for many dioxins/furans have steadily declined over the period with analytical advances. As discussed in a separate telephone conference call between EPA and representatives ofthe MCPATaskForce Three, EPA should make a specific request to technical registrants for additional data. The MCPA Task Force Three believes thatthe Holt et al. paper cited by EPA is superseded by specific information available on EPA registered technical MCPA products. 

### EFED response: A more detailed and accurate accounting for the amounts ofthe dioxins/furans congeners in formulations ofMCPA would allow comparison to concentrations previously determined to be sufficient to be ofenvironmental concern. Ifthe concentrations ofdioxins/furans in an MCPA product fall belowthese identified thresholds, those formulations will be cleared as a dioxin source ofconcern. Ifthey are not cleared, more effort will need to be applied regarding dioxin contribution from these sources. 

### MCPA TaskForceThree comment (page 10): EPA Comment: "It is 

### likely thatsome unknownpercentage of theMCPA detected in surface water andgroundwatermonitoringdata may result from degradation of MCPB to MCPA. Therefore, in the eventof uncertainties regardingMCPA andMCPB usepattern overlap, EFED will assess an impactthedegradation of MCPB to MCPA on monitoringdata, EDWCs, andaquaticEECs, in a conservative manner." TaskForce Response: The overlap in use patterns ofMCPAand MCPB is application to peas. Due to the cost ofthe herbicides and the potential for crop injury, it is extremely unlikely that full rates ofbothMCPA (0.375lb ae/A) and MCPB (1.5lb ae/A) would be applied. Labeling clarifying this situation would likely be agreeable to registrants. As described in a previous comment, there are occasions when a grower may use a very lowrate ofMCPA with a reduced rate ofMCPB to lowerthe treatment cost versus a full rate ofMCPB alone. For example, an indicative productregistered in several countries contains 1part MCPA to 15 parts MCPB. 

### EFED response:We appreciate the comment onthe overlap ofMCPA and MCPB use and will incorporate it, as appropriate, at the time ofthe risk assessment. 

### MCPA TaskForce Three comment (page 10): Page 15, Table 5 - Dissociation Task Force Response: A comment is absent in the "Sufficientfor EFED?" column. What is the answer? 

### EFED response: The data are sufficient. 

### MCPA TaskForce Three comment (page 11): Page 16, Table 

### 5- Volatility-laboratory and Page 17, paragraph 1 EPA Comment: "

...dry soil, with sufficient

- moistureto stillmaintain microbialactivity, and mostsoilin a highertemperature are recommendedto be tested. Task Force Response: A clarification onthe Rationale for Additional DataNeed is requested. The previously submitted study MRID 47075203 was conducted at 25 

### ± 2 °C in soils at 40-60% ofthe 0.33 bar moisture capacity atflow rates of 100 and 300 mL/minute. This study was classified as acceptable. The request is for a dry soil, with sufficient moisture to still maintain microbialactivity, andmost (moist?) soil in a higher temperature are recommendedto be tested. Soils at 40% ofthe 0.33 bar moisture capacity are normally considered dry soils for agricultural purposes. Testing for volatility in soils dryerthan this would normally be considered to be testing in soils that were too dry for agricultural purposes and therefore an environmentnot intended for use ofthe pesticide. Itmay be possible to conductthe study at a higher temperature but since no volatility otherthan carbon dioxide was observed at_25 

### ± 2 °C after a period of 15 days at a flow rate of300 mL/minute it is unlikely that a doubling ofthetemperature in the study would result in any appreciable volatilization which was observed to be at the LOD (<0.02%) in the trapping solutions. 

### EFED response: EFED believes the volatility data for MCPA EHE at low moisture content and hightemperature are still needed. However, EFED will consider any citable sources ofinformation that support the registrant's general statement that low soil moisture and I orhigh temperature would not be occurring at an agricultural field where MCPA is applied.



### EFED Response to Comments Submitted by the Centerfor Biological Diversity (CBD) (EPA-HQ-OPP-2014-0180-0020) While three specific comments were received from CBD regarding the reregistration ofMCPA, all three addressed EPA'sresponsibilities under the Endangered Species Act (ESA). For·clarity, the general comments are included below, but a general response is provided to address all three.CBD comments: I. EPA Has an Independent Duty Under the Endangered Species Act to Consult with the U.S. Fish and Wildlife Service and National Marine Fisheries Service on the Reregistration ofMPCA. II. The EPA Must Make Defensible "NotLikelyto Adversely Affect" and "Likelyto Adversely Affect" Determinations as a Prerequisite for Defensible "Jeopardy" and "No Jeopardy" Determinations. III. EPA and the Services Must Assess the Adverse Impacts ofMPCA in Critical Habitat. EFED response: Regarding CBD's request for EPA to begin informal consultation with the Services immediately after the workplan for MCPA is finalized, EPAplans to follow the March 2013 stakeholder engagement paper ("Enhancing Stakeholder Input in the Pesticide Registration Review and ESA Consultation Processes and Development ofEconomically and Technologically Feasible Reasonable and PrudentAlternatives") to identify the appropriate time for initiation of consultation, either formal or informal, with the Services. The stakeholder engagement paper, jointly developed by the EPA, USDA, and the Services and available at http://www.regulations.gov/#!docun1entDetaii:D=EPA-HQ-OPP-2012-0442-0038, allows for early interaction with the-Services under informal consultation. EPA and the Services acknowledge that early interaction as part ofinformal consultation may result in refinements to EPA's effects determinations that can improve the efficiency ofthe ESA complianceprocess. For example, EPA may involve the Services atthe earliest stages ofregistration review. In general, EPA plans to initiate formal ESA consultation, ifnecessary, at the final decision stage in the registration review process. Consulting later inthe process allows the EPAto develop more refined ecological risk assessments and to engage stakeholders in discussions that should result in more focused consultationpackages that may include risk mitigation for listed species. 

### EFED Response to Comments Submitted by Central Valley Regional Water Quality Control Board (EPA-HQ-OPP-2014-0180-0021) Central Valley Regional Water Quality Control Board comment: In orderto prevent water quality impairments caused by MCPA we are requesting the following action inregistration review: • Considerthe cumulative risk ofadditive toxicities between MCPA and otherphenoxy herbicides. EFED response:EPA appreciates the needto address cumulative risk from mixtures ofpesticides both within and across modes ofaction. EPA, FWS, and NMFS collectively engaged the National Academy of Sciences (NAS) onthe issue ofmixtures as part ofthe broader approach to conduct ESA compliantpesticide risk assessments. As noted by the NAS report, the ability to quantitatively assess risk from mixtures (tank, formulated product, and environmental) is perhaps the most daunting challenge facing EPA and the Services. EPA currently considers cumulative mixture toxicity where data are available on combined effects from one ormore compounds. EPA acknowledges that mixtures represent a considerationthat may influence the toxicity ofthe active ingredient; however, there are many uncertainties and limitations to quantitatively assessing the impact ofmixtures onthe overall risk picture. As the NAS noted, there are significant challenges to incorporation ofmixtures analyses into the risk assessment process including the lack ofa genericpeer-reviewed method to assess the risks from mixtures, uncertainty on the temporal aspects ofexposure to mixture constituents (e.g. each constituent behaves differently once in the environment), lack ofknowledge about mechanism ofaction in non-targets, and uncertainty onthe portability ofobserved interactions across taxa. EPA and the Services have made the issue ofdeveloping an approach for assessing mixtures toxicity apriority for future risk assessments.