UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

MEMORANDUM

Date: March 3 1 , 2015
Subject: Response to Pu blic Comments Received Regarding EPA Endangered Species

Assessment for 2,4

- D Choline Salt in Arkansas, Kansas, Louisiana, Minnesota, Missouri, Mississippi, Nebraska, Oklahoma, Tennessee, and North Dakota a

Product Name: Enlist Duo TM
EPA Registration Numbe r: 62719

- 649
Application Date: November 1, 2011

On October 1 6 , 2014 the Environmental Protection Agency (EPA) published for comment an Endangered Species Assessment regarding the proposed use of Enlist Duo in the following 10 states: Arkansas, Kansas, Louisiana, Minnesota, Missouri, Mississippi, Nebraska, Oklahoma, Tennessee, and North Dakota. However, EPA is not going forward at this time with registering Enlist Duo for use in Tennessee.

The initial Enlist Duo registration allowed use in 6 states: Illinois, Indiana, Iowa, Ohio, South Dakota, and Wisconsin. The only proposed change to the Enlist Duo registration under consideration on October 1 6 , 2014 was the addition of the 10 new states, and the only new evaluation done by EPA concerning this chan ge was the Endangered Species Assessment published for comment on October 1 6 , 2014. EPA did not solicit comments outside the scope of the Endangered Species Assessment for the 10 new states. EPA previously considered comments on the original Enlist Duo r egistration and addressed them in the original registration decision and response to comments document. The original registration decision, response to comments document, and a ll of the materials supporting the original registration are available in Docke t ID: EPA

- HQ

- OPP

- 2014

- 0195 , as is the Endangered Species Assessment regarding the addition of the 10 new states. Comments received during this public participation process not

a Although EPA published for comment, on October 15, 2014, an Endangered Species Assessment regarding the proposed use of Enlist Duo in the 10 states of Arkansas, Kansas, Louisiana, Minnesota, Missouri, Mississippi, Nebraska, Oklahoma, Tennessee, and North Dakota, EPA is not going forward at this time with registering Enlist D uo for use in Tennessee.related to the Endangered Species Assessment pertaining to the 10 new states ar e not discussed

in this response.
The Agency received 34,526 comments in response to this public participation process. The EPA welcomes input from the public during the decision process when amending pesticide registrations, and is committed to thorough ly evaluating and mitigating any potential risks from registered pesticides, consistent with applicable statutory standards. Also, EPA strives to document and explain the basis of its regulatory decisions through public documents.
The majority of the co mments received were outside the scope of this action

– the Endangered Species Assessment for the 10 (now 9) additional states

. EPA notes that its previous response to comments addresse d virtually all of these concerns. Commenters are referred to Docket ID: EPA

- HQ

- OPP

- 2014

- 0195 for those responses and any additional information regarding the decision to register Enlist Duo.
Relevant comments concerning the Endangered Species Assessment that were raised for the additional states are discussed below

1. “No e

ffect ” determinations are arbitrary and capricious because they follow the old system. (i.e., species within the action a rea were found to be not affected if there were no indirect or direct effects pertinent to the species ) and did not follow the Na tional Academy of Sciences report recommendations regarding pesticide mixtures; sublethal, indirect, and cumulative effects; and surrogate species

.
As stated in a recent report to Congress submitted by EPA, the National Marine Fisheries Service (NMFS) , th e U.S. Fish and Wildlife Service (USFWS), and the U.S. Department of Agriculture (USDA):

“EPA scientists used highly conservative and protective assumptions to evaluate ecological risks for the new uses of 2,4

- D in Enlist Duo. The assessments confirm tha t these uses meet safety standards for pesticide registration, and as approved, will be protective of non

- target species, including endangered species.”
Interim Report to Congress on Endangered Species Act Implementation in Pes ticide Evaluation Programs ( “Interim Report”) at 20 (Dec. 11, 2014) , available at http://www.epa.gov/oppfead1/endanger/2014/esa

- reporttocongress.pdf . Additionally, the Interim Report shows that the co mbined agencies acknowledge that EPA’s evaluation of 2,4

- D in Enlist Duo was appropriately based on EPA’s “Overview Document

- compliant endangered species assessment for new herbicide tolerant crop uses” ( Id

. at 22), referring to EPA’s Overview of the Eco logical Risk Assessment Process in the Office of Pesticide Programs , U.S. Environmental Protection Agency

– Endangered and Threatened Species Effects Determinations (“Overview Document”) (January 23, 2004), available at http://www.epa.gov/oppfead1/endanger/consultation/ecorisk

- overview.pdf

.2. EPA’s determinations that listed species are not expected to occur in a n action area is

arbitrary and capricious. EPA may not limit the scope of the action area to the treated field, EPA must consult if it is known that the chemical will move off the field.

EPA relied on U

. S. Fish and Wildlife and National Marine Fisheries S ervice s (the Services) location information, habitat informa tion, and the results of the screening assessment (with risk mitigation measures in place) to establish the relationship of species locations with the expected area where the pesticide exposure would rise to the point where effects were reasonabl y expected to take place for any taxonomic group. The Agency makes no claim that drift and runoff do not occur. The Agency characterized the levels of exposure to drif t and runoff and determined tha t , with mitigations in place, exposures high enough to cause acute or chronic effects are not reasonably expected to occur i n aquatic systems adjacent to treated fields, nor to any place suitable for wildlife adjacent to fields for any taxonomic group. The Agency clearly stated in the screening assessment that exposures were only above levels of concern to organisms on treated fields.
EPA used the available terrestrial and aquatic listed species locations by state and the available habitat requirement information from the Services to compare with the locations of treate d use sites. If a species did not occur in a county where the use sites occur, the species was reasonably expected to have no effects because it was not co

- located with the use site. If a species was in a county where the use site was located , it was ass umed that it was possible it could be co

- located with the action areas (the area where effects occur is defined by the geographical extent where exposure would elicit effects to any taxonomic group) and that further evaluation was necessary to determine if this was actually the case . In such situations the Agency consulted biological information from the Services to determine if the species occurred within the action area.

If according to the Services, a li s ted species was an aquatic species without a t errestrial phase , it was expected to occupy an aquatic environment, and the screening

- level risk assessment found no exposures sufficient to elicit effects in aquatic environments

. Consequently, the Agency concluded aquatic species are not in the action a rea. If a listed species was a terrestrial organism in any phase according to the Services, i t was assumed to occupy habitats that were not otherwise managed to the exclusion of listed species (i.e. areas not paved, not enclosed by structures, or areas in row crop). Since the steps above found that mitigations prevented pesticide exposure to rise to levels reasonably expected to cause effects in areas other than the treated use site, no effects would occur to these off

- field organisms. Exposure could sti ll occur, just not at levels that would trigger any effects concerns for any taxonomic group. For species for which USFWS information suggeste d occurrence on a use s i t e at any time during their life cycle , the Agency turned to the biology of the species t o determine whether species

- specific information would refine the screening

- level risk conclusions. If the effects expected on the field were not directly related to direct effects to the listed species, did not affect any resource the species needed, nor upon reassessment of the risk calculations show a species

- specific finding that expos ures rose to a level of concern , the Agency concluded “ no effect .”3. Exposure to the pesticide alone is enough to conclude a “may a ffect.” Reliance on RQ values to make this determination is inappropriate. As noted above in response to Comment #1, a recent report to Congress submitted by EPA, NMFS, USFWS, and USA stated:

“EPA scientists used highly conservative and protective assumptions to evaluate ecological risks for the new uses of 2,4

- D in Enlist Duo. The assessments confirm that these uses meet safety standards for pesticide registration, and as approved, will be protective of non

- target species, including endangered species.”
Interim Report at 20 (Dec. 11, 2014 ). Additionally, the Interim Report shows that the combined agencies acknowledge that EPA’s evaluation of 2,4

- D in Enlist Duo was appropriately based on EPA’s “Overview Document

- compliant endangered species assessment for new herbicide tolerant crop uses” ( Id

. at 22), referring to EPA’s Jan. 23, 2004

“ Overview Document” regarding endangered and threatened species effects.

4. The Agency did not use or review ECOTOX data.

T he Agency rel ied on previously evaluated data sets from earlier 2,4

- D risk assessments , which included ECOTOX data

.
5. The Agency faile d to allow for uncertainty in th e analysis of effects to honeybees and the

non
- definitive endpoints for other taxa.
The honeybee data and other non

- definitive data were used as surrogate toxicology informa tion for non

- target species, including listed species. Non

- definitive data were “greater than” values, meaning that the highest toxicity level tested did not result in an acute endpoint (i.e., the LD 50 is greater than the highest concentration of 2,4

- D th at was tested). The Agency relied on the best available data within the confines of data sets f rom previous 2,4

- D risk assessments. Exposure estimates were compared to the available data and showed exposure levels below what was reasonably and conservati vely expected to be effects endpoints.

6. The Agency did not accou nt for the combined effects of g lyphosate and 2,4

- D

. The Agency looked at available 2,4

- D/glyphosate combined data from the scientific peer

reviewed literature and registrant

- submitted infor mation for mammal, freshwater invertebrates and freshwater fish and found no combined effects that exceeded the expected effects of glyphosate or 2,4

- D individual ly

.
7. EPA failed to consider glyphosate effects.
Since the registration of Enlist Duo does not contain any new use for glyphosate, as it has been registered for use on genetically engineered corn and soybeans for several years now and is presently used on the majority of those crops’ production acres , EPA did not conduct a new assessment for the glyphosate portion of Enlist Duo

. Also, EPA’s decision did notauthorize any change in when, where, how, or how much glyphosate can be used from what

is already authorized under FIFRA

.
8. Indiana bat. EPA arbitrarily used assumption s of farm field forag ing frequency to reduce exposure levels below the concern threshold. EPA , by admitting that 2,4

- D exposure would occur

, is bound to make a “may a ffect ” determination.

EPA undertakes a careful and extensive scientific analysis in all of its ESA

- related pesticide effects analyses, as it did here. The Agency begins its screening level assessments by conducting a basic ecological risk assessment. That assessment uses broad default assumptions to establish estimated environmental concentrations of particul ar pesticides

. If that screening level assessment results in a determination that the pesticide has no effect on listed species, EPA preserves its limited resources by stopping there. On the other hand, where the screening level assessment does not resul t in a no effect finding, EPA then uses increasingly specific methods and exposure models to refine its estimated environmental concentrations. At each screening step, EPA compares the more refined concentrations to the toxicity of the pesticide active in gredient to determine whether the pesticide exceeds levels of concern established for listed aquatic and terrestrial species. EPA determines that there is “no effect” on listed species if, at any step in the screening level assessment, no levels of concer n are exceeded. If, after performing all the steps in the screening level assessment, a pesticide still exceeds the Agency’s levels of concern for listed species, EPA then conducts a species

- specific assessment to make effects determinations for individua l listed species. That assessment, unlike the screening level assessment, takes account of species’ habitats and behaviors to determine whether any listed species may be affected by use of the pesticide.
EPA followed this careful and methodical tiered ap proach here. In 2013, EPA performed a screening level risk assessment of the proposed new uses of 2,4

- D in Enlist Duo. The Agency subsequently refined its endangered species risk assessment based on spray drift mitigation language that Dow AgroSciences a dded to the Enlist Duo label at EPA’s request

. Specifically, EPA noted that the spray drift language would limit drift by requiring end users to utilize a particu lar nozzle and mix formulation. This language also required end

- users to employ a substantia l buffer when the wind is blowing toward any area that is not a field in crop cultivation, paved area, or area covered by buildings and other structures.
EPA next took into account species

- specific biological information as it relates to the timing of Enl ist Duo applications (and thus potential exposure to 2,4

- D). EPA’s refined analysis observed that Indiana bats typically forage in closed to semi

- open forested habitats and forest edges and pr efer to forage in wooded areas. A ranking of the foraging use of habitats suggested the following order of foraging preference: (a) roads; (b) forests; (c) riparian areas; (d) gras slands; (e) agricultural areas. EPA’s refined analysis went on to analyze the likelihood that the bat could use agricul tural land as a so urce of prey. EPA concluded that the bat could make use of agricultural land as a source of prey and roost in patches of fragmented forest that are adjacent to cor n and soybean fields. The extent of foraging over agricultural land, however, would be less than the degree of foraging around the canopies of forested areas.EPA conservatively estimated that 33% of the bat’s diet could be consumed ov er agricultural

lands. EPA incorporated this and other data, such as the metabolized energy in bat prey, the d aily food ingestion rate scaled to individual bat bodyweight, and the agricult ural application rate of 2,4

- D. Taken together, EPA’s analysis established a complete exposure pathway for Indiana bats to 2,4

- D for those times when the bat d oes forage over tr eated fields. EPA concluded that no bat would experience even one day of exposure exceeding the applicable toxicologic al threshold. Accordingly, EPA determined that the 2,4

- D component of Enlist Duo would hav e no effect on the Indiana bat.
Again, as not ed above in response to comment #1 and #3, a recent report to Congress submitted by EPA, NMFS, USFWS, and USA stated:

“EPA scientists used highly conservative and protective assumptions to evaluate ecological risks for the new uses of 2,4

- D in Enlist Duo. The assessments confirm that these uses meet safety standards for pesticide registration, and as approved, will be protective of non

- target species, including endangered species.”
Interim Report at 20 (Dec. 11, 2014 ). Additionally, the Interim Report s hows that the combined agencies acknowledge that EPA’s evaluation of 2,4

- D in Enlist Duo was appropriately based on EPA’s “Overview Document

- compliant endangered species assessment for new herbicide tolerant crop uses” ( Id

. at 22), referring to EPA’s Jan. 23, 2004

“ Overview Document” regarding endangered and threatened species effects.

9. Louisiana Black Bear. Despite the screening

- level assessment trigger for concerns, the Agency made up additional components to its illogical assessment to reach a “ no effec t .” These kind of specific biological assumptions are outside of EPA’s expertise and are suspect.
Once the screening level assessment and co

- location analysis suggested the bear was potential ly at risk, the Agency compared available biological/behavioral data identified in the literature and in USFWS sources to determine if the exposure assumptions employed in the conservative screening assessment were biologically appropriate for the bear. Based on this review, more relevant exposure inputs were develop ed for the bear (i.e., seasonal timing of when the bear is expected to use agricultural fields) and the risk assessment was refined to reflect these additional lines of evidence. The re fined analysis indicated that the exposures were overestimated in the screen , and exposures under more biologically relevant conditions were below levels of concern.

10. Whooping Crane. EPA did not reproduce the calculations for this 10

- state assessment that was done for the previous six states. EPA did n ot conduct a chronic assessment nor consider residues on all the food items consumed by the crane.

The chronic assessment for all bird species (including the whooping crane) was included in the screening risk assessment and found no risk concerns for birds; o nly concerns fo r acute effects were identified. The assumptions at the screening

- level are intentionally moreconservative than species

- specific analyses; thus , the lack of chronic concerns at the

screen ing

- level indicated that further refinement would not identify risk and was not necessary . EPA did not repeat all the calculations in the 10

- state assessment because the findings in the previous assessment were based on identical assumptions of exposure and toxicity regardless of the state in which the species occurs. Co nsequently, citing the documents in which these analyses were contained was appropriate.
The dietary analysis was performed on the food item that contained the highest 2,4

- D residues. By assuming that 100 percent of the diet was made up of the food item with the highest residues, the analysis is protective of food items with lower residues as well.

11. Mississippi Sa ndhill Crane. The assessment i gnored chronic effects nor did it consider residues on all of the food items in the crane’s diet . The RQ fell j ust below the level of concern, so EPA should check its fuzzy math. Given the sensitive status of the crane (located on and adjacent to the Mississippi Sandhill Crane National Wildlife Refuge), Enlist Duo should not be registered in Mississippi.

See Comm ent 10 for a response to the chronic effects and dietary analyses . The Agency applied the level of concern analysis in an objective manner. The resulting exposure

- to

effects ratio is below the concern level t hat t he Agency has used under the evaluation
a pproach selected for this assessment

. Consequently, “no effects” are expected for the Mississippi Sandhill Crane.

12. Lesser Prairie Chicken. The Agency failed to conduct a chronic effects assessment. EPA ’s attempts t o pretend to understand lesser prairie c hicken biology by citing a few random scientific journal articles is laughable, absurd, and otherwise arbitrary and capricious.

See Comment 10 for a response to the chronic effects analysis . EPA relied on publically available published information that described the extent to which the lesser prairie chicken uses agricultural environments. These findings were compared to the assumptions made in the screening assessments and all lines of evidence lead to a conclusion that the species would not be exposed to 2,4

- D choline salt at the levels that were assumed in the screen. This initiated a more biologically

- relevant exposure estimate that resulted in a finding that exposures fell below the concern level for this species. EPA did not find any data showing agricultural field use by the species from USFWS reports and citations made in those reports or reports citing t hose references.

13. Gopher Tortoise. The Agency did not complete a chronic assessment. Exposure demonstrates that the species is affected.

B irds are used as surrogates for reptiles under the assessment approach when d a ta are unavailable for reptiles (USEPA 2004)

. Birds are likely a conservative surrogate for exposure to pesticide residues via the diet due to their higher metabolic rate as war m

- blooded creatures compared to cold

- blooded reptiles, which suggests that food consumption rates, andtherefore dietary pesticide consumption rates, would be higher for birds. Furthermore, with

respect to chronic assessment and its reproductive endpoints , both birds and the majority of reptiles are egg

- layers representing very similar exposure scenarios en

- ovo. The screening assessment found no c hronic concerns for birds and thus no chronic concerns for reptiles.

14. American B urying Beetle. There are no e stablished levels of concern for terrestrial invertebrates, presumably because EPA seeks to register pesticides that kill terrestrial invertebrates. EPA cites DP4 11614 as reason for “no effect” and it is not in the record. EPA did not consider direct eff ects (i.e., brushing up against treated plants) to the beetle.
The Agency has established an interim level of concern of 0.05 that has been used for litigation assessments and other endangered species risk assessments. Direct effects to terrestrial inv ertebrates (e.g., the American burying beetle) were assessed in the screening

level risk assessment and EPA concluded that direct effects were not a concern. Therefore, only indirect effects to the American burying beetle were considered in the refined
en dangered species analysis because direct effects had already been screened out (see whooping crane response for more discussion on screening assessments). EPA did not repeat the analysis for the American burying beetle in the 10

- state assessment because t he findings in the previous assessment (6

- state endangered species assessment, DP411614) were based on identical assumptions of exposure and toxicity regardless of the state in which the species
occurs. Consequently, citing the DP barcode of the document in which this analysis was contained was appropriate. DP411614 was placed in the docket in April 2014 (EPA

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OPP

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- 005).

15. Spring Creek Bladderpod. By EPA’s own tortured logic
, the pesticide cannot be approved for use in Wilson County , TN. En list Duo should not be registered in Tennessee.
EPA is not going forward at this time with registering Enlist Duo for use in Tennessee.

16. EPA did not consider populations of its eleven identified listed species that are being reintroduced or expanding r anges into areas of the states where corn and soybean are grown. In reaching effects determinations, the Agency referred to species recovery plans, species 5

- year reviews, and United States Fish and Wildlife Service (USFWS) county

- level summaries of occur rence. A species was considered if USFWS information indicated endangered or threatened populations were located within any of the states included in this assessment.

17. The Agency failed to assess adverse modification or destruction of critical habitat.

E ffects for any biologically mediated process are likely limited to the area where exposure to the herbicide rises to the level of affecting one or more ta xo nomic groups. The Agency demonstrated that effects are limited to the ag ricultural field, and possibly paved areas and areas enclosed by structures. Consequently, critical habitat effects for any s pecies would be limited to the areas where biological effects on a single individual co uld be reasonablyexpected to occur (i.e ., treated fields, paved areas, and areas enclosed by structures ). A

detailed analysis is provided in the addendum to the 2,4

- D choline salt assessment on corn and soybean

– critical habitat analysis (USEPA 2015, D425283, Docket ID: EPA

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2014

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- 3688 ).

18. EPA’s assumption that spray drift will remain confined to the field because of the spray drift mitigation language is flawed. Similarly, EPA claims that there will be no 2,4

- D choline salt in surface waters and that “the proposed 2,4

- D choline uses are not expected to

ov erlap with rivers, streams, creeks, or other water bodies.”
The Agency makes no claim that spray drift or runoff will not occ ur ; rather it states that with mitigations in place, exposures high enough to cause acute or chronic effects are not reasonably ex pected to occur i n aquatic systems adjacent to treated fields, nor to any place suitable for wildlife adjacent to fields for any taxonomic group. The Agency based the spray drift mitigation on empirical field data with Enlist Duo as well as the considerat ion of habitats for non

- target organisms. Given that 2,4

- D choline salt use is restricted to corn and soybean fields that are in agricultural production, no water bodies are expected to be within the action area ( i.e., the field). Consequently, this is a reasonable rationale for the “no effects” determinations for aquatic species.

19. Non

- target species may move on and off the field during spraying. The Agency has not indicated how the 168 endangered plant and animals in its 2,4

- D assessment would be inform ed of these field boundaries so as to remain off of the field.
The Agency’s endangered species analysis considered whether a species would be on the field at any time , based on species

- specific biology and habits, taken from USFWS’ and National Marine Fis heries Service’s documents . Consequently, those species that may move on and off the field were captured in this analysis and considered as being “on” the field.

20. Effects of the whole product, Enlist Duo (including active ingredients and the additional

un identified ingredients) have not been assessed. In addition, synergistic or additive effects of Enlist Duo with atrazine or other commonly used herbicides have not been assessed. Risk to terrestrial plants and other organisms have been underestimated bec ause formulation data are not available. Indirect effects, such as loss of critical food, forage and nesting sites resulting from reduced plant diversity associated with increased spraying of the whole product, Enlist Duo (separately and in combination wi th other pesticide products) has not been assessed.
The response to public comments for the initial registration of Enlist Duo on corn and soybeans includes a more detailed analysis on the potential for synergy between the 2,4

- D choline salt and glyphos ate (Document ID number EPA

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- 2414). In summary, i f effects data are available for a formulated product containing more than one active ingredient, they may be used qualitatively or quantitatively in accordance with the Agency’s Overview Do cument and the Services’ Evaluation Memorandum (USEPA 2004;USFWS/NMFS/NOAA 2004)

. Acute oral rat data were available for the Enlist Duo product

as formulated and did not indicate any additive or synergistic effects when compared with 2,4

- D by itself. Be cause the available data showed no indication that the tested results would be different for untested species, this conclusion was extended to all animal taxa

. For animal taxa where Enlist Duo formulation data were not available, the most sensitive 2,4

- D acid/salt/amine endpoint was used, as a protective surrogate. For terrestrial plants, formulation data were available for a number of other 2,4

- D products; the most sensitive of these was selected to represent the toxicity of Enlist Duo. The Agency does not routinely assess tank mixes, consequently, Enlist Duo tank

- mixed with atrazine or other commonly used herbicides was not assessed.
The spray drift mitigation language on the label is expected to keep exposure levels below the threshold of concern to any species off of the field. Consequently, only indirect effects that take place on a treated corn or soybean field needed to be considered. This was included in the endangered species risk assessment

. 21. The Agency did not follow its own guidance doc ument for honeybee toxicity assessment and thereby underestimates the risks to bees and other beneficial insects. Specifically, indirect (e.g., effect of reduced flowering plants for foraging) and direct exposures, the differential sensitivity of larvae c ompared to adult bees, sub

- lethal effects that may affect brood and colony health, and differences in sensitivity when exposed via that contact or oral route were not considered. These data gaps should be filled before approving the registration of Enlist Duo. EPA inappropriately classifies 2,4

- D as “practically non

- toxic” to honeybees and fails to consider sub

- lethal effects, and the importance of these on hive health and colony collapse disorder. 2,4

- D could also affect other important insect species

su ch as monarch butterflies. Glyphosate was not included in the assessment.
The response to public comments for the initial registration of Enlist Duo on corn and soybeans includes a honeybee analysis in accord with the Agency’s Pollinator Risk Assessment Framework and includes adult acute oral and contact data ( ID# EPA

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2014

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- 2414). The analysis indicated that risk concerns are not expected for acute exposures to adult honeybees. Sub

- lethal signs of toxicity in the contact study included lethar gy and loss of equilibrium in a total of three bees at the highest treatment level. The loss of equilibrium was only observed at the 24 hour observation period and the lethargy was only observed at 72 hours. For the acute oral study, reduced coordination was the only sub

lethal effect noted in the three highest treatments at 4 hours (2, 1, and 5 b ees at 23.2, 42.0 and 62.6 μg ae /bee treatment levels). At the 24 hour and 48 hour observation periods, only 1 bee was affected in each of the two highest treat ment groups. Overall, the sub

- lethal effects appear limited and it is unlikely that they would translate into whole colony effects given their limited magnitude.
Agency policy is that any pesticide with an acute LD 50 > 11 μg ae/bee is considered “prac tically non

- toxic” to honeybees, based on mortality. Generic data gaps for larvalhoneybees and chronic exposures to adults are being considered as part of the ongoing

Registration Review process.
The endangered species assessment considered both direc t and indirect risk concerns (for example, risk concerns for flowering plants) in its analysis, including those to honeybees, monarch butterflies, and other terrestrial invertebrates.
Since the registration of Enlist Duo does not contain any new use for g lyphosate, as it has been registered for use on genetically engineered corn and soybeans for several years now and is presently used on the majority of those crops’ production acres , EPA did not conduct a new assessment for the glyphosate portion of Enlist Duo

. Also, EPA’s decision did not authorize any change in when, where, how, or how much glyphosate can be used from what is already authorized under FIFRA

. 22. Large

- scale spra ying of 2,4

- D would contaminate and poison plants and animals in the vicinity of the sprayed fields, leading to economical and environmental damage. The spray drift assessment is impaired by EPA’s reliance on models rather than real

- world data.
The Enlist Duo label approved by EPA contains enforceable spray drift mitigation requir ements that will prevent 2,4

- D choline salt from moving off the field in concentrations high enough to exceed our levels of concern in non

- target species, including listed species. EPA uses the best available data and models in its spray drift assessments . The mitigation requirements are based on Enlist Duo specific field and laboratory data; the spray drift analyses were tailored specifically to the Enlist Duo use patterns, environmental conditions, and formulation data. If additional data become availa ble, EPA will consider it for incorporation into future analyses, as appropriate.

23. There are multiple gaps in the 2,4

- D volatilization and spray drift data that were submitted to the Agency. The data that do exist indicate that there may be risks for ter restrial plants and for endangered species of mammals and birds from 2,4

- D drift off the treated fields.
See the response to public comments for the initial registration of Enlist Duo ( ID# EPA

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- 2414) for a robust discussion of the spray dr ift and volatilization data available for the 2,4

- D choline salt and the lines of evidence used to arrive at conclusions. The screening

- level assessment was designed to be very conservative and flagged potential risk concerns for terrestrial plants, mamma ls, and birds. Upon refinement of the assessment using species specific information (i.e., body weight, species location, timing of species’ use of agricultural fields), it was concluded that “no effects” are anticipated for endangered species in the 8 st ates in which the Agency is registering Enlist Duo for use at this time.

24. EPA did not consider the effects of increased use in 2,4

- D that will occur if Enlist Duo is registered on corn and soybean in AR, KS, LA, MN, MO, MS, NE, ND, OK, and TN.The ecolog ical risk assessment and endangered species risk assessment assume an organism

is exposed to the maximum amount of 2,4

- D choline salt that is possible (terrestrial and aquatic exposure pathways), given that the label directions are followed. Consequently, the risk assessment is protective and does not need to be adjusted for the actual number of acres that are treated with Enlist Duo.

25. Risks associated with runoff of Enlist Duo are not adequately assessed by EPA

. On October 10, 2014, the Agency issued an addendum that characterized the amount of runoff that would be expected from the proposed 2,4

- D choline salt uses. Using PRZM/EXAMS, it was determined that the amount of runoff expected from the corn and soybean uses is <1% of the applied mass. This is w ell below the assumptions made by the TerrPlant model, which was used as a Tier 1 screening

- model for risk concerns. Through this analysis EPA found that concentrations of 2,4

- D choline in runoff will not present a concern to terrestrial plants. See USEP A 2014 (D423309) for more details of the analysis.

26. Metabolism of 2,4

- D within Enlist corn and soybeans creates a new route of exposure to residues and metabolites that EPA does not address for listed and non

- listed species

.
EPA did not assess the metab olites of 2,4

- D because the toxicity of and exposure to 2,4

- D acid was expected to be higher, and thus pose greater risk concerns, than the metabolites. The 10

- state risk assessment ( Addendum to 2,4

- D Choline Salt Section 3 Risk assessment: Refined Enda ngered Species Assessment for Proposed New Uses on Herbicide

- Tolerant Corn and Soybean for AR, KS, LA, MN, MS, MO, NE, ND, OK, TN ,” found in Docket ID: EPA

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- 2419) for terrestrial organisms assumes that 100% of residues are 2,4

- D and that th e appropriate toxicity endpoints are relative to the free acid. The acute lethal and reproduction mammalian endpoints used in assessment were 441 mg ae/kg

- bw and 55 mg ae/kg

- bw/day, respectively. For birds, the acute lethal endpoint was 218.7 mg ae/kg

bw and the reproduction endpoint was 962 mg ae/kg

- diet. By comparison , available mammalian data ) on the acute lethal endpoint for the metabolite 2,4

- dichlorophenol (2,4

- DCP) is 580 mg/kg

- bw (1.3 times less toxic) (EHC, 1989) and the reproduction data endpoi nt is 134 mg/kg

- bw/day (2.43 times less toxic) (Aoyama et al., 2005). There exist reports for more potent mammalian acute measures of 2,4

- dichlorphenol for molten product, e.g. 44 mg/kg (NTIS OTS0534822 1991), but these are not representative of an oral a dministration expected from its conversion in a biological matrix.
Under the most conservative assumption of degradation, one mole of 2,4

- D choline (221.04 g) yields one mole of 2,4

- dichlorophenol (163.0 g) for a mass ratio of 0.738. Consequently, the c onversion of mass to 2,4

- dichlorophenol is about 74% of the corresponding residue assumption for 2,4

- D ae on the field. However, data submitted to the Agency and reviewed by the Health Effects Division (HED)[ USEPA 2011, D384441 Summary of Analytical Chem istry and Residue Data for Use of 2,4

- D Choline in/on Herbicide Tolerant Field Corn Containing the Aryloxyalkanoate Dioxygenase

- 1 (ADD

- 1) Gene. Health Effects Division, Office of Pesticide Programs, Environmental Protection Agency”, found in Docket ID: E PA

HQ

- OPP

- 2014

- 0195

- 0037 ; USEPA 2013, D400085 Summary of Analytical Chemistry and Residue Data for Use of 2,4

- D Choline in/on Herbicide Tolerant Soybeans Containing theAryloxyalkanoate Dioxygenase

- 12 (AAD

- 12) Gene . Health Effects Division, Office of

Pest icide Programs, Environmental Protection Agency, found in Docket ID: EPA

- HQ

- OPP

2014

- 0195

- 0005] on soybean and corn indicated that no more than 18.4% of recoverable residues were 2,4

- dichlorophenol and its conjugates in forage, and no more than 9.15% in
s eed (corn was non

- detect).
An example of the impacts of these findings to a risk assessment can be seen with the Indiana bat. Assuming that 2,4

- D choline salt has been converted to 2,4

- dichlorophenol (plus conjugates) at a rate of 18.4%, the exposure val ue (excluding any differences in absorption or metabolism in the insect prey) would be 18.4% of the assessment for 2,4

- D choline. Toxicity values would be lower by 9.36 for acute toxicity and higher by a factor of 2.43 for reproduction. Therefore, the ac ute RQ, under the most conservative approach would be:
2,4

- dichlorophenol acute RQ assuming total conversion of 2,4

- D to 2,4

- dichlorophenol: (RQ for 2,4

- D choline 0.06) (1/1.33)(0.184) = 0.008
2,4

- dichlorpophenol reproduction RQ assuming total conversion of 2,4

- D to 2,4

- dichlorophenol: (RQ for 2,4

- D choline a.e.0.47) (1/2.43)(0.184) = 0.036
Both the acute and chronic RQ are below levels of concern (acute LOC = 0.1; chronic LOC = 1). This analysis does not consider the potential for differential in absor ption of plant associated 2,4

- dichlorophenol and its conjugates. Pascal

- Lorber et al. (2012) compared the metabolic fate of [(14)C]

- DCP, [(14)C]

- residues from radish plants, and purified [(14)C]

- DCP

- (acetyl)glucose following oral administration in rats. These authors found that rat absorption of plant

- associated 2,4

- dichlorophenol metabolites was lower from the plant matrix than plant

- free conjugates and DCP itself.
The combined effects of lower toxicity and limited residues in corn and soybean forage and seed results in risk quotients for the in

- plant degradates that are well below levels of concern. Assuming all exposures as parent 2,4

- D choline or its acid equivalent remains the most conservative approach.

References Aoyama, Hiroaki; Hojo, Hitosh i; Takahashi, Ken L.; Shimizu, Naoko; Araki, Masayuki; Harigae, Michiko; Tanaka, Naoki; Shirasaka, Noriko; Kuwahara, Maki; Nakashima, Nobuaki; Yamamoto, Eri; Saka, Machiko; and Teramoto, Shoji. 2005. A Two

- Generation Reproductive Toxicity Study of 2,4

- Dich lorophenol in Rats. Jour. Toxicol. Schi. 30, Special Issues, 59

- 78.
EHC (1989) Chlorophenols Other Than Pentachlorophenol. Environmental Health Criteria (EHC) 93, IPCS, section 8.1. http:// www.inchem.org/documents/ehc/ehc/ehc093.htm

. National Technical Information Center (NTIS). 1991. Initial submission: toxicologic investigation of: 2,4

- dichlorophenol (final report) with cover letter. Dated 11/26/91, 11NTIS OTS0534822.Pascal

- Lorbe r S; Despoux S; Jamin EL; Canlet C; Cravedi JP; Laurent FJ. 2012. Metabolic fate

of 2,4

- dichlorophenol and related plant residues in rats. Agric Food Chem. 2012; 60(7):1728

- 36 (ISSN: 1520

- 5118).
Taylor, L. 2015. Personal communications via e

- mail from Linda Taylor, USEPA Health Effects Division to Meghan Radtke, USEPA Environmental Fate and Effects Division, March 10 and 11, 2015.

USFWS/NMFS/NOAA. 2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act Section 7 Consultation Regulations; F inal Rule. Federal Register Volume 69. Number 20.Pages 47731

- 47762. August 5, 2004.

USEPA . 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency. Listed and Threatened Species Effects Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. January 23, 2004.
USEPA. 2011. Summary of Analytical Chemistry and Residue Data for Use of 2,4

- D Choline in/on Herbicide To lerant Field Corn Containing the Aryloxyalkanoate Dioxygenase

- 1 (ADD

- 1) Gene. Health Effects Division, Office of Pesticide Programs, Environmental Protection Agency. Docket ID: EPA

- HQ

- OPP

- 2014

- 0195

- 0037.

USEPA. 2013. Summary of Analytical Chemistry an d Residue Data for Use of 2,4

- D Choline in/on Herbicide Tolerant Soybeans Containing the Aryloxyalkanoate Dioxygenase

- 12 (AAD

- 12) Gene . Health Effects Division, Office of Pesticide Programs, Environmental Protection Agency. Docket ID: EPA

- HQ

- OPP

- 2014

- 019 5

- 0005.
USEPA. 2014. Addendum to 2,4

- D Choline Salt Section 3 Risk Assessment: Refined Terrestrial Plant Exposure Estimates and Effects Determination. Environmental Fate and Effects Division, Office of Pesticide Programs, Environmental Protection Agenc y. EPA

- HQ

- OPP

- 2014

- 0195

- 2413

. USEPA. 2015. Addendum to 2,4

- D Choline Salt Section 3 Risk Assessment: Designated Critical Habitat Modification Determinations for Proposed New Uses on Herbicide

- Tolerant Corn and Soybean for AR, IL, IN, IA, KS, LA, MN, MS, MO, NE, ND, OH, OK, SD, TN, and WI. Environmental Fate and Effects Division, Office of Pesticide Programs, Environmental Protection Agency. Docket ID: EPA

- HQ

- OPP

- 2014

- 0195

- 2419.