1 OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

August 26, 2014

PC Codes: 117401, 117403, 117404, 117423

MEMORANDUM DP Barcode: 421881

SUBJECT: Response to Public Comments on th e EFED Registration Review Problem Formulation for Clopyralid

FROM: Elyssa Arnold, MEM, MPH, Biologist James Lin, Environmental Engineer

Environmental Risk Branch 2

Environmental Fate and Effects Division (7507P)

REVIEWED

BY: Jean Holmes, DVM, MPH, Risk Assessment Process Leader R. David Jones, Senior Agronomist

Environmental Risk Branch 2

Environmental Fate a nd Effects Division (7507P)

THROUGH: Brian Anderson, Branch Chief

Environmental Risk Branch 2

Environmental Fate a nd Effects Division (7507P)

TO: Steven Snyderman, Chemical Review Manager Tracy Perry, Team Leader Patricia Parrott, Branch Chief Risk Management and Implementation Branch 3

Pesticide Re-Evalua tion Division (7508P)

The Environmental Fate and Effects Division (E FED) reviewed comments from the technical registrant (Dow AgroSciences) on the “ EFED Registration Review Problem Formulation for Clopyralid ” (Document ID EPA-HQ-OPP-2014-0167- 002, referred to as the Problem Formulation in this document). EFED also revi ewed the registrant’s comments on the Clopyralid Preliminary Work Plan for Registration Re view (Document ID EPA-HQ-OPP-2014-0167-010)

that were relevant to the Probl em Formulation. The purpose of this memorandum is to respond to these comments. EFED appreciates the comments and has considered them carefully; responses are provided below each set of paraphrased comments.2 Comments on Preliminary Work Plan Rele vant to the EFED Problem Formulation

1. Requested Data

Dow AgroSciences (DAS) Comment: DAS plans to generate new data for the followi ng with clopyralid acid technical material:

 Guideline 850.1300 Chronic Fr eshwater Invertebrate

 Guideline 850.2100 Avian oral t oxicity (passerine species)

 Guideline 850.4500 Aquatic non-vascular pl ant growth for 2 additional species:

 Skeletonema

, Navicula

 Guideline 850.6100 ILV for soil method

 Guideline 850.6100 ECM and ILV-compost

DAS plans to submit existing study data for the following:

 Guideline 835.4100 Aerobic Soil Metabolism

 Guideline 835.4300 Aerobic aquatic Metabolism

 Guideline 850.1400 Freshwater Fish early-life stage

 Guideline 850.2300 Avian reproduct ion (upland game species)

 Guideline 850.4400 Aquatic Vascular Plant growth

 Guideline 850.4550 Cyanobacteria toxicity

 Guideline 850.6100 ECM for soil

 Guideline 850.6100 ECM and ILV for water

EFED Response: It appears that DAS has conducted guideli ne fate and ecotoxicity studies that it has not submitted to the Agency. DAS is encour aged to submit any available studies relevant to ecological risk assessment, not limited only to the eight studies noted above. EFED will review the data when it is received by the Agency.

2. Terrestrial Plant Data with Clopyralid Acid and Salts

DAS Comment: Comments addressing the foll owing data requirements:

 Guideline 850.4100 Terrestrial plan t toxicity, seedling emergence

 Guideline 850.4150 Terrestrial plan t toxicity, vegetative vigor DAS proposes to continue to rely on existi ng data MRID 40081401 and supplement it with data for formulation EF-243. Where no typical end use pr oducts exist for the stra ight clopyralid salts we do not propose to con duct the above studies.

EFED Response: EFED has classified the seedling emer gence and vegetative vigor studies in MRID 40081401 as supplemental due to a num ber of methodological limitations. These

limitations were listed in DER amendments tran smitted by EFED to the Registration Division on February 21, 2012 (DP398834). Among other defici encies, these studies did not report plant weight measurements and, therefore, did not measure a potentially sensitive endpoint for terrestrial plants exposed to clopyralid. MRID 40081401 does not fulfill the guideline requirement for tier 2 vegetative vigor and seedling em ergence data for clopyralid. These studies

are needed to assess risk to non- target terrestrial plants.3 For the clopyralid acid (PC 117403), EFED notes that, contrary to the statement in Table 1 of the comment document, DAS does currently have an ac tive registration for a si ngle active ingredient product ( i.e. , not co-formulated); this registration is for Lontrel Turf and Ornamental, EPA Reg. No. 62719-305. For the monoethanolamine (MEA) salt (PC 117401), EFED will evaluate the seedling emergence and vegetative vigor studie s using EF-243 against OCSPP guidelines when they are submitted. For the clopyralid trie thylammonium (TEA) salt (PC 117404) and the potassium salt (PC 117423), EFED concurs that ther e are currently no active registrations for single active ingred ient products ( i.e. , not co-formulated).

EFED’s objective in requesting terrestrial plant st udies using formulations containing each of the four registered clopyral id active ingredients ( i.e. , PCs 117403, 117401, 117404, and 117423) is to identify any differences in toxicity of thes e chemicals. Where no appropriate formulations exist for this purpose, i.e. , for PCs 117404 and 117423, studies may be conducted with the technical products. If DAS has other information they believe will address this uncertainty, they are encouraged to submit it for review.

3. Terrestrial Plant Data with Clop yralid Co-formulated Products

DAS Comment: Comments addressing the foll owing data requirements:

 850.4150 Terrestrial plant toxicity, vegetative vi gor co-formulated with other herbicides DAS proposes to provide existing data for GF -1362 and conduct studies for Curtail, Sendaro, Surestart II, Hornet WDG, and Hat Trick Th ree Way. Clopyralid-conta ining products from multiple registrants typically have similar co mpositions of active ingredients and thus DAS proposes that the above representative formulatio ns should be adequate for products registered by DAS and other registrants. Li sted formulations, surrogate or other, containing 3 active ingredients are also expected to cover the require ments for a subset of the same actives provided they have a similar compositional range.

EFED Response: EFED will review the studie s with the proposed formulations when they are submitted to the Agency.

Comments on the EFED Problem Formulation

4. Groundwater Incidents and Modeling

Stated in the Proble m Formulation (p. 4): Incidents reported for other picolinic acid herbicides demonstrate the potential for groundwater contamin ated with these herbicides to damage nontarget terrestrial plants when the groundwater is used for irrigation.

DAS Comment: We are not aware of any incidents relate d to damage to non-target plants via groundwater contamination with clop yralid and would be interested to evaluate if the incidents mentioned can be attributed to picloram only wh ile being used at the historical higher rate.

The agency intends to use the PRZM-GW mode l to estimate water concentrations in groundwater, for use as inputs into drinking water and non-target plant risk assessments. Recent4 presentations have shown that proper paramete rization of PRZM-GW is critical to yield representative estimates of predicted concentr ations. The characterization of soil sorption has been found to be especially critical and it ha s been found that including a time-dependent formulation of the sorption greatly improves the predictive power of the model (as compared to field data). The current implementation of PRZM-GW, however, does not support this representation, but various groups have shown th at this can be accomplished quite readily. In keeping with EPA’s statements that “additiona l data are recommended to better understand the potential for risk due to residues of clopyral id,” Dow AgroSciences proposes parameterizing PRZM-GW assessments using best available information and methodology. DAS will undertake

further field studies or monito ring efforts if refined modeling efforts do not yield sufficient refinements of exposure.

EFED Response: EFED agrees in principl e that a tiered study appr oach can be useful for refining risk estimates. EFED completed some se nsitivity analysis on inco rporation of nonlinear sorption and degradation in subsurface soil laye rs using the PRZM-GW model, to determine the usefulness of conducting additiona l studies in refining risk es timates. EFED explored the potential for considering nonlinear sorption and a degradation rate in su bsurface layers.

EFED recommends if any additional analyses are pe rformed, that these analyses focus on better understanding/quantifying the potential for degrada tion in subsurface layers (either via longer term hydrolysis studies or degradati on in soils from subsurface layers).

It is likely that whether i nputs to PRZM-GW can be refine d or not, the compound has the potential in vulnerable ar eas to reach groundwater at concentra tions that could result in a risk concern if the water is used to irrigate sensitiv e terrestrial plants. In the absence of additional data, EFED will use PRZM-GW to estimate the pot ential exposure to terrestrial plants from residues in irrigation water obtained from groundwater sources.

5. Monitoring Data

Stated in the Problem Formulation (p. 13): A search of the NAWQA database (11/25/2013) returned maximum detection levels for clopyral id of 0.53 ppb in surface water in Oregon and 0.42 ppb in groundwater in Washington. Data provided by the Montana Department of Agriculture include maximum detection levels for clopyralid of 0.80 ppb in surface water and 2.8 ppb in groundwater. The measured concentrations in groundwater ar e higher than the previously

modeled concentration.

DAS Comment: The maximum level in the NAWQA data base was a sample from 1995 and was one of only 4 detects in 6803 sampling incidents in the database. When the maximum detected level (0.53 ppb) is compared to the lowest human Health Benchmark for pesticides calculated for clopyralid (990 ppb) in 2013 reflecti ng the latest scientific inform ation, concern for exposure to clopyralid via ground or surface water is not anticipated.

EFED Response: Available monitoring data will be consid ered in the ecological risk assessment and risks from exposure to clopyra lid via drinking water will be assessed by the Health Effects

Division.5 6. Label Ambiguities

Stated in the Proble m Formulation (p. 6): The labels have non-sp ecific use sites.

DAS Comment: DAS agrees with this Agency comment and has initiated label amendments to

better define use sites.

EFED Response: EFED will assess uses consistent with the updated labels at the time of the preliminary risk assessment.

7. Aerobic Soil Metabolism Half-life

Stated in the Proble m Formulation (p. 15): In Table 7, Aerobic soil metabolism DT50 (25±1°C) 12.8 days (MRID 43891403).

DAS Comment: The DT50 in the cited study should read 7.8 days at 25 °C not 12.8 days.

EFED Response: The new half-life value of 8.03 days is calculated based on “Standard Operating Procedure for Using the NAFTA Guid ance to Calculate Representative Half-life Values and Characterizing Pesticide Degradation.” 1

1 Bohaty, Rochelle, William Eckel, Katrina White, and Dirk Young. 2012. Standard Operating Procedure for Using

the NAFTA Guidance to Calcul ate Representative Half-life Values and Ch aracterizing Pesticide Degradation. Office of Pesticide Programs, U.S. Environmental Protection Agency. Available online at: http://www.epa.gov/oppefed1/ecorisk_ders/degrada tion_kinetics/ftt_sop_using_nafta_guidance.pdf.6 8. Avian Reproduction Study with the Mallard Duck

Stated in the Problem Formulation (p. 18): Results from the avian reproduction study with the mallard duck (MRID 00156001) included statistically significant effects on normal hatchlings per eggs set and per eggs laid at the lowest tr eatment concentration (100 ppm) and statistically significant effects on 14-day old survivor we ight at the lowest and middle treatment concentrations (100 and 330 ppm). No effects were seen at the highest treatment concentration (1000 ppm), and therefore these st atistically significant effects were not considered to be treatment related. This study is scientifically sound and classified as acceptable. A low-dose effect (hormesis) is another po ssible explanation for the study re sults. Reproduction data for an additional avian species may help to illumi nate the likelihood of this possibility

DAS Comment: DAS plans to submit the following study:

 Dabbert, C.B., Mitchell, R.B., and Oberheu, D.T. (1997). Northern Bobwhite Egg Hatchability and Chick Immunocompetence fo llowing a Field Application of Clopyralid.

Bulletin of Environmental Contam ination and Toxicology 58: 801-806. The objective of this study wa s to determine if field application of clopyralid at the recommended label rate would alter viability and hatchability of eggs and subsequently, growth and immune function of 28 day-ol d Northern bobwhite chicks.

EFED Response: EFED will review the study and determine whether it is sufficient to fulfill the 850.2300 guideline requirement when it is submitted.

9. Ecological Incidents – Residentia l Turf Uses of Clopyralid

Stated in the Proble m Formulation (p. 19): Incident I010414-001: Ther e is a warning on the label saying that compost contai ning grass clippings that have been treated with clopyralid should not be used in the gr owing season of application.

DAS Comment: This incident was reported at a time when clopyralid was registered for use on residential turf. The work done by Vandervoort, 1997 indicates that was an appropriate statement and shows decline of clopyralid residues from 32,000 ppb to 1,400 ppb in 365 days. This label

statement became obsolete as residential turf use was voluntarily removed by Dow AgroSciences from all clopyralid labels in 2002. From that time clopyralid-containing products could only be used by professional applicators on golf courses a nd other forms of non-residential turf, such as commercial complexes, road medians and soccer fields.

EFED Response: The incident report provides an exampl e of clopyralid pe rsisting at toxic levels through a composting process. Only labeled uses will be assessed in the risk assessment.

10. Clopyralid Residues in Compost

Stated in the Proble m Formulation (p. 21): Clopyralid has been found to survive the composting process when yard clippings are co llected and composted. The chemical becomes concentrated in the final compost, which then ma y be toxic to plants to which it is applied.7 DAS Comment: The appearance of ‘concentration’ of cl opyralid in compost may be an artifact of the differential rate of decay of the chemical and the compost feed stocks as they are biologically degraded. The effect of the decay of the compost and the residue concentration increase needs to be accounted for by bring the com post back to a constant standard (ash basis).

EFED Response: The results of a degradation study in compost will address the issue as to whether clopyralid will be concentr ated in the final compost.

11. Treated Trees in Compost

Stated in the Problem Formulation (p. 22): Trees treated with clopy ralid may be used as

compost.

Dow AgroSciences Comment: Clopyralid is labeled for use on woody species pests such as mesquite, locust and acacia. The geographical scope of such use implies that these trees are unlikely to be close to compos ting facilities. Trees such as mesquite are unlikely to be preferential feedstock fo r composting facilities.

EFED Response: EFED will take this information into account in the risk assessment. Potential

use of trees treated with cl opyralid as woodchips or mulch will also be considered.

12. Dissipation Study in Compost

Stated in the Problem Formulation (p. 23): No n-guideline Study: Dissipation in Compost. A study is requested to demonstrate the rates of degradation and leaching in vegetative and manure composts. The study will be used to char acterize the risk from clopyralid residues in compost and may demonstrate potential mitigations such as compost holding times. The absence of information on the persistence of clopyralid residues in composted plant material or animal manure prohibits a quantitative assessment of the potential risk to non-target taxa posed by the application of composted material containing these residues. A prot ocol is requested for review before the study is conducted.

DAS Comment: DAS feels that existing data has answer ed all the questions put forward by the Agency and further studies are not required. Labe ling restrictions based on said data have effectively ensured no large scale repetition of events in 2002. Our comments are outlined in 3

sections:

A. Existing data for vegetative composting showin g that the questions from the Agency have already been answered for appropriate inputs to compost of feedstocks that may contain clopyralid, degradation of cl opyralid if it does contaminat e feedstock and appropriate composting conditions to maximize rem oval of clopyralid from compost.

B. Current label restrictions for all products. If clopyralid la beling is followed no clopyralid should enter waste streams used for compost feedstock.

C. Lack of clopyralid residues expected in composting using manure feedstocks. DAS regulatory animal metabolism studies inform th e expected lack of clopyralid in manure.8 Dow AgroSciences respectfully suggests that su fficient data exists th at would render any new non-guideline study unnecessary. Clo pyralid does indeed decompos e in compost, composting conditions can be enhanced to increase the sp eed of clopyralid degradation in green waste compost and compost that has been contamin ated with clopyralid can be remediated by reactivating the degradati on process. The place of bioassays in agronomic practices is important for protection of succeeding crops and determination of plant back intervals. The same practice should be considered BMP for compost feedstock in take. Finally enforcemen t of current existing label language should ensure that clopyralid contamination of compost feedstock is unlikely as growers follow and understand the labeli ng restrictions al ready in place.

EFED Response: The fate and transport properties of clopyralid are not well understood in compost environments. The compost study will allo w EFED to ascertain wh ether the application of compost materials will damage vegetation. Dow is encouraged to submit any currently existing data on clopyralid fate transport propert ies in compost and mulch in addition to the requested study.