UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WA SHING TON D. C., 20460

PC Code: 128850 DP Barcode: D413093

MEMORANDUM March 10, 2014

Subject: Response to Comments on the Preliminary Ecological Risk Assessment for Glufosinate-Ammonium

To: Shirley Keel

, Acting Team Leader Linda Arrington, Branch Chief Risk Management and Implementation Branch V Pest i cide Re-Evaluation Division**(7508P ~**  /} 

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From: Chuck Peck

, Envi r onmental En ineer

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## -f.- Catherine Aubee, Biologist '3 ·11> 

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Environmental Risk Branch 4

Through: Jim Carleton, Ph.D., Senior Scientist

# A~**c~** :3/Jo/'Jul'f
Thomas S t eeger, Ph.D., Senior

## Scien**~~d -rf_u_~** **g/;o/~o/</** Sarah Winfield, Acting Branch Chief · ·**ti7 tt**  

### (/ Envi ronment a l Risk Branch 4 Envi ronmental Fa t e and Effects Division Office of Pesticide Programs

The Environmental Fate and Effects .Division (EFED) has reviewed the comments submitted

re garding the preliminary ecolog i cal ri sk assessment conducte d as part of the registration review of t he herbicide glufosinate

- am monium (PC Code 1 28850). The preliminary ecological risk
assessment wa s posted to the public docket (EPA-HQ-OP P- 2008-0 190) for public comment on March 6, 2013. The comment s addressed in this memorandum were from th e registrant, Bayer CropScience (BCS, EPA-HQ-OPP-2008-0 190-0038 ), and the Center for F ood Safety (CFS, EPA-HQ -OP P-2008-0190-0031 ). Ba sed on comments received and EFE D 's responses (contained in this memo)

, EFED will consider the recommendations i n revising the ecological risk assessment of glufos i nate-ammonium.

In the section below, comments are paraphrased and EFED's response to each of the comment follows.

1 of212 of 21 BCS Comment 1, page 6:

“BCS requests EPA to re

- evaluate all the use patter n s using parent and MPP as stated in ROCKS [Residues of Concern Knowledgebase Subcommittee] and to re

- evaluate rice by considering [the] PFAM [Pesticides in Flooded Application Model] with index reservoir, since this level of refinement has already been evaluated by EFED and promoted in previous presentations at the Exposure Modeling Public Meet ing (Rice Modeling: A Case Study, 10/30/2012, presentation not made during meeting; presentation made 3/19/2013). By considering the index reservoir refinement, the acute EDWC [estimated drinking water concentration] will be reduced to less than 160 μg/L a nd less than 40 μg/L for chronic. There is a possibility that based on this level of refinement; rice may no longer be the crop that will be driving the exposure assessment.”

EFED Response:

EFED is currently evaluating the use of PFAM coupled with the i ndex reservoir in its drinking water assessments for uses on rice. It is anticipated that a decision will be made in the 2014 calendar year regarding the applicability of PFAM . The case study modeling results referenced by Bayer and pr esented at the Expo sure Modeling Public Meeting ( EMPM ) , as well as in EFED’s refined drinking water assessment of glufosinate

- ammonium for rice (DP Barcode 387412, May 2012) were intended to serve as a means of characterizing qualitative ly the potential reduction of estimate d drinking water concentrations (EDWCs) due to dilution. As such, the quantitative use of PFAM coupled with the index reservoir is not warranted at this time.

In 2010, EFED conducted a drinking water assessment for agricultural uses of glufosinate

ammoni um using the total toxic residue approach (DP Barocde 372624, June 22, 2010). In th at assessment, the chronic EDWCs for rice use exceeded the human health drinking water level of

concern (DWLOC)

, thereby requiring a refined assessment specifically for use on rice (DP Barcode 387412, May 2012). The refined assessment for use on rice evaluated only exposures from the parent and MPP, as a more recent ROCKS meeting determined that these were the only residues of concern. After the use on rice, the next highest chronic EDWC ( 66 μg/L ) was for use
on grapes, and was below the DWLOC for human health , even when using the TTR approach

. As such, c onducting an other drinking water assessment for the other use patterns, evaluating only parent and M PP, would not change the conclusions.

B CS Comment 2 , page 6:

“BCS notes that EPA did not conduct the rice exposure assessment using the aquatic dissipation half

- life for glufosinate

- ammonium. Nor did EPA give any consideration to the very short water half

- life derived in the study (3.0 days, MRID 45204403). This half

- life demonstrates that the potential for chronic exposure in the rice paddy is significantly less than the estimates provided in the EPA risk assessment.”3 of 21 EFED Response:

As outlined in E FED’s response to comments in 2011 (DP Barcode 387412, October 28, 2011), use of an aquatic dissipation half

- life to represent chemical decay would be inappropr iate

, because dissipation reflects multiple fate processes that operate concurrently. EFED empl oys model s whose inputs include half

- lives reflecting various specific degradation mechanisms and/or representative environmental compartments ( e.g. , aerobic aquatic degradation )

. The purpose of conducting an aquatic field dissipation study is “to determine the extent of dissipation and mobility of pesticide residues under actual use conditions ” (OCSPP Guideline 835.6200)

. Dissipation, defined as “the overall process leading to the eventual disappearance of substances from the site of its applicati on or an environmental compartment” (OCSPP Guideline 835.6100), is a combination of transport processes, such as volatilization

, sorption, leaching, etc ., and transformation via microbial metabolism, hydrolysis, photodegradation

, etc

. The PFAM refined ric e model uses aerobic soil degradation, aerobic aquatic metabolism, and sorption coefficients to estimate rice paddy concentrations. Use of a dissipation rate in place of a rate for one of these specific mechanisms

, w ould comprise “double count ing ” a loss process. Additionally, the results from an aquatic dissipation study represent a specific site and field condition s, whereas EDWCs

are intend ed as conservative representations of exposure applicable in national

- scale assessment

. The aquatic field dissipa tion stud y in question used fields flooded at a 12

- inch depth ; however, rice paddies are typically flooded to smaller depth s ( i.e
., between 4 and 8 inches )

. T he deeper flood depth employ ed in the aquatic field dissipation studies thus dilut ed the test chemical to a greater degree than would typically occur in a rice paddy, which illustrates how t he dissipation
rate at a specific site may not be conservative or even representative of other sites. Lastly, both the Liberty ® and Liberty ® 280 labels allow f or use of glufosinate

- ammonium at higher application rates (approximately 1.44 lbs a

. i

. /A for rice seed propagation ) than those used in the aquatic field dissipation study ( i.e
., 2 applications at 0.44 lbs a

. i

. /A)

. Because maximum use rates were not emplo yed during the study, the resulting concentrations and dissipation rates

can not be assumed to be reflective of such use rate s

. It should also be noted that the submitted aquatic field dissipation study has other deficiencies

, particularly with respect to the analytical method validation and the storage stability data.

The drinking water assessment for glufosinate

- ammonium use on rice ( DP Barcode 387412, May 30, 2012), from which the paddy water concentrations were derived, estimated that if the maximum co ncentrations measured in the aquatic field dissipation study were adjusted to reflect a 4

- inch paddy water depth, the maximum glufosinate

- ammonium concentrations in the water would be between 93 and 288 μg/L

. The s e values were in line with the range of co ncentrations estimated using modeling ( i.e
., 83 to 390 μg/L ) , although th e latter wer e based on a higher application rate

.

B CS Comment 3 , pages 6

- 7:

“ BCS notes the following difference in the Efate parameters f or glufosinate [

- ammonium] and requests EPA to review the corresponding MRIDs in order to compare the calculated half

- lives with those reported by BCS in this Table. ”4 of 21 Table 1 . Summary of Efate properties for glufosinate

- ammonium (excerpted from BCS commen ts).

EFED Response:

In 2010, EFED retrieved the studies and data evaluation records (DERs) for the studies listed in Table 1 . At the time, EFED planned to estimat e drinking water concentrations for glufosinate

ammonium based on total toxic residues (TTR ; glufosinate

- ammonium plus its three degradates: 2

- methylphosphinico

- acetic acid

, 3

- methylphosphinico

- propionic acid , and 2

- acetamido

- 4

- methylphosphinico

- butanoic acid )

, and needed to calculate half

- lives reflecting TTR rather th an parent chemical . EFED also re

- e valuated the half

- lif e estimate s for parent glufosinate

ammonium

, since many of the DERs , which were written in the early 1990s

, cited the study authors’ half

- lives without validating them

. U sing a log

- linear regression of the individual replicate percent age s of radioactiv ity attributable to glufosinate

- ammonium versus time, EFED

re vised the reported half

- lives. Table 2 summarizes the half

- lives as originally estimated by the study authors in the cited studie s , and the revised half

- lives used by EFED in its assessment

. It should be noted that EFED’s revised half

- lives for MRIDs 43123119, 40345659A, and 40345660 were also provided in the Problem Formulation for glufosinate

- ammonium (DP Barcode 345696, January 9, 2008).

T able 2 . Summary of half

- life estimates by study authors and EFED values for glufosinate

- ammonium

. Study Soil designation Study Author Half

- life (days) EFED Half

- life (days)

43123119 Sandy loam V Sandy loam 2 Loamy sand 2.2 3.7 8.3 6.4 8.5 8.7 8.8

40345659A 1 Sandy loam V Sandy loam S Silt loam E 23.3 20.7 21.7 23.0 20.6 21.4

40345660 2 Sandy loam system Sand system 46.5 and 51.7 29.1 and 35.2 57 38

45204402/01 3 Loam system Sand system (1 ppm) Sand system (0.1 ppm) 11 42 2 10.9 86.5 1.4

1. It is unclear how the values cited in BCS’ table were derived. Values in table were extracted from study.5 of 21 2. For each system depicted, two replicates were conducted and the s tudy authors derived half

- lives for each replicate. EFED combined th e replicates and developed a representative half

- life for each system. It is not clear how the values reported in the BCS table were derived.
3. The numbers presented in the BCS table reflect those presented in the EFED DER for the study using a non

- linear single first order method. The values reported in the table above reflect those presented by the study authors.

EFED believes the half

- lives used in the assessment for the parent glufosinate

- ammonium are consistent with those developed in the studies and allow for estimation of pr otective aquatic concentrations

.

B CS Comment 4 , pages 7

- 8:

“ BCS notes that EPA did not model the same use patterns as was conducted for the aquatic exposure assessments and reflected in Table 3.1 [of the preliminary risk assessment] , this is especially true for the non

- agricultural uses. Additionally, BCS notes that these values need to be updated to match the use pattern information provided in Appendices 1 and 2 of these comments.

EPA states the default foliar dissipation half

- life is 35 days. They also note that the data submitted under OCSPP Guideline 860.1500 were not deemed appropriate for determining a foliar half

- life. BCS in its evaluation of the studies available found 16 trials that can be used to derive half

- life. While these trials (corn, canola, sugar beet and [p] asture grass) were not conducted in the United States, they were conducted in areas with similar weather patterns and therefore are representative of use patterns fo r the US. [h] alf

- life valu es ranged from 1.9 to 11.1 days , with a mean on short/tall grass of 4.4 days and overall mean 5.5 days. BCS will be submitting the following report in support of the derivation of the foliar half

- life (Sabbagh and Demarteau, 2011)

. ”

EFED Response:

EFED will revise the ecological risk assessment using the updated use patterns provided in BCS’s Appendices 1 and 2

. EFED will review the studies submitted by BCS regarding foliar dissipation and, if acceptable, consider the se data in the ecological risk assessment.

B CS Comment 5 , page 8:

“ BCS notes that the fish early life stage test was not included in the Data

- Call

- In for glufosinate [

- ] ammonium. However we will be conducting a fathead early life stage test (and associated
acute test) for the European data requirements study during 2013.

With regards to the NOEC [no observed effect concentration] and LOEC [lowest observed effect concentration] from the trout 21 [

- ] d test, BCS believes the NOEC and LOEC should be 100 and 500 μ g a.i ./L(nominal, which could be converted to mean measured). The only effect observed at the 100 μ g a.i./L concentration was some slow reactions, but only on Day 2 and for the duration of the test.6 of 21 BCS notes that the algal species used for the metabolite test s [discussed in Table 3.2.1 of the risk assessment] varied, depending on the metabolite, either Desmodesmus or Pseudokirchneriella were used. ”

EFED Response:

The Agency looks forward to the submission of the fish early life stage data. The risk assessment and associated DER will be revised to clarify that the no observed adverse effect concentration ( NOAEC ) and lowest observed adverse effect concentration ( LOA EC ) values for the 21

- day toxicity test with juvenile rainbow trout ( Oncorhynchus mykiss ; MRID 48301105 ) are based on sublethal measurement endpoints (behavioral effects) and not survival. Slow reactions were observed in all fish from the 100 mg/L (nominal) exposure level on Day 2. The study author reported that since this observation occurred only once, it was not considered treatment

related. However, slow reactions were not observed in control fish . Moreover, slow reactions were observed in u p to three surviving fish exposed at 500 mg/L (nominal) on Days 1 through 4

, before subsiding. Therefore , a treatment

- related effect , although transient, cannot be excluded ; therefore, the Agency maintains that the NOAEC for the study is 50 mg/L (nominal) based on impaired behavior

. We assume that the identification of these treatment levels in terms of μ g/L in the registrant’s comments is a typographical error.
With respect to the algal toxicity tests with glufosinate

- ammonium metabolites, the species u sed in each test is identified in the risk assessment.

B CS Comment 6 , pages 8

- 9:

“ BCS would like to note the following with regards to the DNT [Developmental Neurotoxicity] test, and recommends that the morphometric measurements not be used as corrobor ative evidence for evaluating potentially ecologically relevant effects.

• Test levels in the DNT test were: 0, 200, 1,000, or 4,500 ppm (equated to 0, 14, 69, or 292 mg/kg/d). • No effects observed in the following: brain weight, brain gross and microsco pic necropsy, the average onset of preputial separation in males and vaginal opening in females, No treatment

- related changes in Functional Observational Battery (FOB) during any of the testing periods, auditory startle response or learning and memory. • T otal and ambulatory motor activity was increased in males at 4,500 ppm on PNDs [post

- natal days] 13, 17, and 21, in females at 1,000 and 4,500 ppm on PNDs 17, 21, and 61, and in males at 1,000 ppm on PNDs 21 and 61. Corresponding sub

- session interval activity was also increased for these groups on each testing day. • Brain morphometric measurements: [o] nly 1 of 3 measures in the hippocampus showed a difference and that endpoint can be problematic. The difference in the mean length of the ventral limb of the dentate hilus (Level 3) was observed in both males (9

- 15%) and females (12

- 20%) at 200 ppm. No compound [

- ] related changes in other morphometric measurements were observed (PND 21 mean vertical thickness of the cortex on Level 1, mean width of the base of the cerebellar lobule 9 on Level 5, PND 72 mean vertical7 of 21 height between the layers of pyramidal neurons in the hippocampal formation in Level 3, radial thickness of the cortex in Level 3). • With regards to the morphometric difference in ventral limb of the dentate hilus, there was no evidence of an associated functional deficit (Biel maze) at any d ose. Additionally, it should be noted that the endpoint in general has high variability associated with how measurements are made, and that the difference between left & right side measurements in the controls (13%) was greater than the difference between low

- dose and control (9

- 12%). Measurements at the low dose are within the range of historical controls, while the results for controls approach the upper limit of historical control. This measurement is also a relatively poor measure of the structure (hori zontal measure of structure with radial orientation). ”

EFED Response:

EFED has used the DNT as a line of evidence in characterizing the potential effects of glufosinate

- ammonium in mammals; the registrant has not provided a compelling case to discard the results of the DNT study. Therefore, EFED will continue to use the DNT results qualitatively in the risk characterization.

B CS Comment 7 , pages 9

- 10:

“ BCS notes that the risk quotient exceed a nces for the estuarine/marine invertebrates have been conducted with the exposure assessment within the rice paddy. There will not be any estuarine/marine organisms within the rice paddy, the risk assessment should be conducted with the exposure estimate for t he receiving water body. With regards to the quote noted above on tidal flux, only under very specific scenarios (and not necessarily common scenarios) could increase exposure duration take place, but an increase in exposure concentration would not

occur. Of course the incoming tidal flux would increase the dilution of the rice paddy discharge water. Also, tidal flux will not introduce estuarine/marine organisms into the rice paddy unless there is a significant flood event. This type of an event would signi ficantly impact the production of rice and other organisms in rice paddy, as well as any estuarine/marine organisms introduced into the rice paddy. Lastly that flood event (if it were to occur) would significantly dilute the exposure to glufosinate [

- ] ammon ium. ”

EFED Response:

EFED does not agree that exposure to estuarine/marine in vertebrates in the rice paddy c ould not

occur. The sheepshead minnow ( Cyprinodon variegatus ) , the EPA test species for estuarine/marine vertebrates, can exist in shallow freshwater and estuarine/marine environments. There is potential for such organisms to be exposed to glufosinate

- ammonium once paddy water is released. EFED agrees that introdu ction of estuarine/marine species into a rice paddy due to tidal flux would probably only occur in a rare event. However, tidal flux could result in an estuarine/marine species being moved upstream to the outlet of a rice paddy prior to release of the pad dy water, thus resulting in exposure locally to water at concentrations equal to th os e in the paddy.8 of 21 B CS Comment 8 , page 10:

“ BCS acknowledges in EPA’s risk description for aquatic plants (section 4.3.1.3 [of the preliminary risk assessment] ) it is reco gnized that the toxicity values across species ranged from 41μg/L to 100,000 μ g/L. However BCS offers the following comments in the potential for indirect effects, and would state that the probability of glufosinate [

- ] ammonium indirectly having an effect o n organisms through a potential impact on blue

- green algae is very low. • There were no risk quotient exceed a nces for aquatic macrophytes. • The other 4 species of algae tested were significantly less sensitive than the blue

- green algae. If risk quotients were to be calculated for these other species (2 green algae, freshwater diatom, saltwater diatom), there would be no risk quotient exceed a nces (listed

or non

- listed. • Blue

- green algae are a less desirable food item for other aquatic organisms than the other species tested. • If the aquatic field dissipation study water half

- life of 3 days (MRID 45204403) were used in the exposure estimate for rice, the dissipation of parent glufosinate [

- ammonium] would be significantly greater than the current EPA estim ates. Therefore, IF there were a potential impact on this less desirable food item, that species would have the potential for recovery as the glufosinate [

- ammonium] dissipates. • The exposure estimates are within the rice paddy, not for the surrounding aqu atic environments. Therefore the risk to algal species outside the rice paddy is low as the environmental exposure would be significantly less. ”

EFED Response:

Natural algal communities are diverse. Therefore, the Agency consistently requires data for f our species of aquatic nonvascular plants (freshwater and saltwater algae and diatoms) and uses the most sensitive endpoint across species and studies in risk estimation. As stated in EFED’s guidance to its risk as s essors, “risk estimates should be based on the most sensitive of the four unicellular guideline study species independent of presumed ecological compartment” (USEPA 2008 1 ). As with the use of any surrogate species, they are intended to represent the potential sensitivity of a wide range of orga nisms that may not be limited to their specific taxon. It is for this reason that EPA typically requires multiple species of aquatic plants. As such, the sensitivity of Anabaena flos

- aquae is not considered specific to blue

- green algae but is considered representative of other aquatic non

- vascular plants in general.

Because rice paddies may also serve as important habitat for aquatic and semi

- aquatic species, including nonvascular aquatic plants, the Agency maintains that estimated environmental
concentr ations ( EECs ) within the treated rice paddy are relevant to risk estimation. Moreover, the blue

- green alga (cyanobacteria), which was the most sensitive specie s tested with

1 USEPA. 2008. Clarification regarding aquatic plant risk estimation. Memorandum from D. Brady to Environmental Fate and Effects Division, dated 30 September 2008. Washington, D.C.9 of 21 glufosinate

- ammonium , is ecologically important and is critical to the nitrogen cy cle ( Fernández

Valiente and Quesada 2004 2 ).

With regards to aquatic dissipation rate of 3 days, please refer to the earlier discussion regarding the use of dissipation rates as model inputs in lieu of degradation rates . Lastly, while the EECs for rice are taken from estimates of concentrations of water in the rice paddy, these EECs also reflect the concentration of glufosinate

- ammonium in the release water from a rice paddy. Therefore, exposure of algal species directly outside the paddy to these concen trations could

occur.

B CS Comment 9 , page 1 1 :

“ BCS provides the following comments for consideration of the risk to birds, reptiles and terrestrial [

- ] phase amphibians. • EPA did not conduct the assessment (calculate risk quotients) for all the scenarios provided in Table 3.1 of the EPA Environmental Fate and Ecological Risk Assessment for the Registration Review of glufosinate [

- ] ammonium. This is particularly important for the non

- agricultural uses of glufosinate ammonium. • BCS provides updated informat ion on the glufosinate [

- ] ammonium use patterns for further refinement of the assessment. • Sabbagh and Demarteau, 2011 determined the mean foliar dissipation half

- life for glufosinate [

- ] ammonium is 5.5 days. ”

EFED Response:

As discussed in the response t o Comment 3 above, EFED will revise the ecological risk assessment using the updated use patterns provided in Appendices 1 and 2 of BCS’ comment document

. EFED will review the studies submitted by BCS regarding foliar dissipation and, if acceptable, use t he se data in the ecological risk assessment.

B CS Comment 10 , pages 11

- 13:

“ BCS provides the following comments for consideration of the risk to mammals. Collectively (and individually) all of this information demonstrates that the potential risk to mammals is significantly less than that predicted in the preliminary risk assessment.

• EPA did conduct the assessment with non

- agricultural use pattern definitions provided by the registrant and in Table 3.1 [of the preliminary risk assessment] . Appendices 1 and 2 of these comments provides further information with regards to the use patterns for glufosinate [

- ] ammonium.

• BCS provides updated information on the glufosinate [

- ] ammonium use patterns for further refinement of the assessment.

2 Fernández

- Valiente, E., and A. Quesada. 2004. A shallow water ecosystem: ri ce

- fields. The relevance of cyanobacteria in the ecosystem. Limnetica 23 (1

- 2): 95

- 108.10 of 21 • With regards to the ac ute assessment: The exposure of the indicator species in the field (such as herbivorous voles) is better represented by dietary exposure, in which the animals can feed on demand in numerous distinct “meals” over the whole day. With the gavage exposure in t he LD 50 studies the animals received the dose in one single bolus. This is not representative for the field situation, as wild mammals do not ingest their entire daily intake in one meal but rather feed in a diurnal short

- term activity rhythm (Daan & Slops ema 1978 1, Halle 2000 2). Hansson (1971) also concluded that

, e.g . field voles would need at least 15 stomach fillings per day. Thus, wild mammals are exposed to residues ingested in numerous feeding bouts over the whole day, and these ingested residues a re mixed with their diet.

• BCS disagrees with the use of a value of 6 mg/kg/day for the NOAEL of the rodent multi

- generation study. Since there were no relevant effects in male rats, and the effects were similar over generations, it would be appropriate to use the female NOAEL of approximately 9.6 mg/kg/day for the pre

- pairing and gestation periods, the critical periods for the effect observed in the study.

• The use patterns with the highest applications rates (orchards and some of the non

agricultural rates) are all ground application that are highly directed banded application or directed applications around buildings or other objects within the farmstead. These types of applications will have limited off

- target movement and in some cases leave untreated
veg etation in the area (farmstead).

• The glufosinate [

- ] ammonium

- treated vegetation shows very rapid symptoms of phytotoxicity, necrosis followed by plant death (see Figure below). Furthermore a study by Pallet and Gosch (2004) examined the time course for onse t of phytotoxicity to 10 plant species at 1.3 and 0.89 lb/A application rates (BCS will be submitting this study to EPA). Within 4 days, the wilting process is complete in 60% of the species, and after 7 days all monocotyledonous and dicotyledonous plants are completely wilted. The fast wilting process is reducing the food quality of the treated material, because wilted weeds are no longer attractive as feed item to herbivorous animals. The animals will then seek food items from other areas, such as offsite vegetation where no direct applications of the product have been made and potential exposure is significantly reduced due to reduced drift with medium droplet size and drift interception by vegetation.

• Barfknecht (2011a) examined the assumption that wild mammals prefer to feed on the untreated plants rather than on the wilted weeds. The feeding preference of common voles before and after application of [g] lufosinate [

- ] ammonium was analyzed in enclosures with a grass

– flower mixture under semi

- field condit ions. In 2010 and 2011 a seed mixture was sown to grow a meadow which was similar to the vegetation which occurs in the natural habitats of voles. In each year voles from wild populations were equipped with LEDs and released into the enclosure (3 voles in 2010 and 4 voles in 2011). After one week (in 2011) or two weeks (in 2010) of acclimation, 50 % of the area of the semi

- field basin (6 m2) was treated with glufosinate

- ammonium SL200 (1.5 kg a.i./ha). The observation of the voles started at beginning of ni ght and took about 4 hours per session. The semi

- field basins were continuously observed with the night vision device. In 2010, the number of voles observed in the untreated and in the treated part was recorded during each minute. The method was slightly c hanged in 2011. At the end of each minute a scan was performed to record the position of each vole. The protocols of 6 observation sessions were used to analyze the preferences of the voles: day 1, 2 and 511 of 21 after application in 2010 (day +1, day +2, day+5) and one day before application (day

- 1) and day 1 and 7 after application (day +1, day +7) in 2011. All observations showed that after application of [g] lufosinate

- ammonium the voles prefer to spend their time in the untreated area. Quite different from th at finding are the results from the observation performed before application. On that day the voles visited both areas similarly with a slight preference of the predestined treated area.

• Barfknecht (2001b) further examined glufosinate [

- ] ammonium treated fo od acceptance with wild mammals by evaluating whether rabbits will reduce their consumption of wilting vegetation after an application with glufosinate

- ammonium and will prefer fresh green vegetation, which is for example readily available beside the treat ed vegetation stripes in vineyards and orchards. Perennial ryegrass ( Lolium perenne ) was grown in 160 trays (11 g grass seeds on trays with a size of 46 cm x 28 cm). When height of the grass then exceeded a height of about 20 cm, 75 trays were sprayed with glufosinate

ammonium with an application rate of 1.5 kg a.i./ha. The remaining 85 grass trays were used for adaptation of the rabbits and as untreated control food during the test. Two months before the exposure, 9 rabbits were separated into two groups a nd provided a time to acclimate to the test cages (size: 2 m x 2 m x 2 m) and eating fresh cut grass. About three days before exposure initiation, the rabbits were separated and kept individually thereafter until the end of the test. On days 1, 2, 4, and 6 after the spray application, each rabbit received an equivalent amount of freshly cut grass from a treated and from an untreated tray for 2.5 hours. At all other times the rabbits had free access to standard food pellets. Already on day +2 visual differen ces between treated and untreated grass became apparent. The leave tips started to fade. On day +4 and afterwards the treated plants were mostly wilted. On day +1, the rabbits consumed similar amounts of untreated (50.4 %) and treated (49.4 %) grass. From day +2 on the rabbits preferred the untreated grass significantly. On day +6 treated grass was consumed only to 2.2%. The feeding behavior was well correlated with the wilting process: The more the plants wilted, the less treated grass was consumed by the rabbits, demonstrating that wild mammals will seek untreated food.

• With regards to assessing the potential risk to insectivorous mammals, BCS will be submitting a study examining the potential residues of glufosinate [

- ] ammonium to ground beetles after an application of 0.67 lb/A under laboratory conditions. The test item was applied at a rate of 0.67 lb a.i./A on Poecilus cupreus beetles, the food ( Musca domestica pupae) and the substrate (natural soil). After spray application of the test item, the beetles were maintained in the laboratory on natural soil substrate. After defined time intervals, beetles were removed from their exposure units, deep frozen and submi tted to residue analysis. The residues of glufosinate

- ammonium on ground beetles ( Poecilus
cupreus ) declined rapidly after a spray application under extended laboratory conditions. Time

- weighted average concentrations at 7

- , 14

- and 21

- days after the appli cation were calculated at 29.0%, 22.1% and 18.7% of the initially measured concentration, respectively. This study demonstrates that long

- term exposure to glufosinate [

- ] ammonium via exposure terrestrial arthropods does not occur. ”12 of 21 EFED Response:

As noted by the registrant, the Agency consider ed additional use information provided by the registrant in the PRA. Updated use information received in response to the PRA and incorporated into labels will be considered, as appropriate, in the revised risk assess ment.

The Agency considered both oral (gavage) and dietary toxicity data when assessing risk to mammals. Toxicity data obtained through oral exposure are important for most accurately determining the dose at which toxicity is observed; these data are the n used to assess potential toxicity and risk to different size classes of mammals. Dietary toxicity data generally represent a more ecologically relevant exposure scenario, but are less useful for calculating dose

- based estimates of toxicity and risk beca use habitat use, foraging behavior, and physiology vary across mammalian species.

For estimation of chronic risk to mammals, the Agency will continue to use the NOAEL of 6 mg/kg/day. The endpoint was selected based on s tatistically significant (p<0.05) reductions in the number of viable rat pups per litter in both offspring generations (F 1 and F 2 ) in a rat multi

generation dietary exposure study ( MRID 40345612)

. The Agency reviewed the data by Barfknecht (2011 a , MRID 49135801 3 ) and classified the study as appropriate only for qualitative use in the risk assessment. Barfknecht (2011 a ) presents very limited information for ecological risk characterization regarding glufosinate

- treated versus untreated habitat utilization by wild

- caught specimens of a Eur opean vole species. Barfknecht (2011 a ) did not directly evaluate foraging behavior but instead only reported on habitat preference based on duration of presence in the treated or untreated portion of the enclosure. The report states that foraging behavio r was observed both before and after treatment, but this refers to only a single day of pre

- treatment observation in 2011. The sample size was small and the enclosure was not replicated. The study design implied equal availability and proximity of
treate d versus untreated habitat. It is unclear whether observations were performed daily; some observations were excluded from the summary. Neither individual level data nor statistics were reported. It is not stated whether the results shown represent total time of all animals or an average per animal per night.

For each season, Barfknecht (2011 a ) indicates that one more vole was introduced into the enclosure than was marked. The sex of the marked versus unmarked voles was not reported, and it is unclear whether unmarked voles were counted in the observations. Batteries in the LEDs had to be changed after four days; however, it is not stated whether the LED had to be removed and then re

- stitched to the vole during this exchange. The report suggested tha t the 2010 data following battery exchanges were not useful because voles did not emerge from holes after release; the author speculated that the availability of an alternate feed source (oat flakes) when trapped inhibited subsequent foraging behavior. On e of the four marked voles in 2011 lost its LED. Overall, Barfknecht (2011 a ) concluded, “ In all observations performed after the application, the voles preferred the untreated areas in contrast to the observation before

3 MRID 49135801. Barfknecht (2011 a ), Observation of voles ( Microtus arvalis ) under semi

- field conditions after an application of Glufosinate

- ammonium SL 200 (1.5 kg a.i./ha). Report No BAR / FS055; Document No. M

403847

- 02

- 1.13 of 21 application ”. However, this appears to be a subjective and selective conclusion which is not supported by any statistical analysis or by the limited data included in the study report.

In a separate study submitted by the registrant, Barfknecht (2011 b 4 ) concluded that rabbits present ed with treated versus untreated forage preferred the untreated forage. The remaining forage was weighed periodically; weights were adjusted for moisture loss based on the weight loss of a concurrent control forage to which the rabbits did not have access . The study was classified by the Agency as appropriate for qualitative use in the risk characterization. The implication of the study author’s conclusion was that plants which have wilted as a result of herbicide exposure would be less appealing and pos sibly less palatable to herbivore and omnivores. However, such a preference does not preclude the consumption of treated plant material. Moreover, given the national scale of this risk assessment and the relatively small territorial ranges of many smaller mammals, it is unreasonable to conclude that alternative habitat and untreated forage will be available consistently in glufosinate

- ammonium use areas.

The Agency looks forward to any future submissions addressing potential exposure or toxicity of glufo sinate

- ammonium to insectivorous mammals. Such data will be reviewed and, if appropriate, considered in any future ecological risk assessments. With respect to the unsubmitted study on residue decline in ground beetles, which was summarized in the regist rant’s comments on the PRA, the Agency notes that residue decline after a single glufosinate

- ammonium application does not preclude chronic exposure when multiple glufosinate

- ammonium applications may occur.

B CS Comment 1 1 , page 14:

“ BCS concurs with EPA that both the acute oral and contact toxicity values are >100 μ g a.i./bee, and therefore the uncertainty associated with the approach EPA has taken with this preliminary assessment is very high. Using the EECs from TREX [Terrestrial Ex posure model] with multiple applications does not consider the life span of the organism or the flowering duration of exposed plants, and has resulted in a significantly overly conservative exposure estimates. BCS recommends that EPA conduct the assessment using the recently revised bee risk assessment methodology released by the EPA. The documentation associated with the EPA methodology makes it clear that the multiple applications do not need to be considered given the short life span of bees and the shor t period individual flowers remain viable. ”

EFED Response:

The preliminary risk assessment identified uncertainties regarding potential risk to listed species of terrestrial invertebrates. Although contact exposure to glufosinate

- ammonium in the laborat ory did not cause toxicity to the young adult honey bee ( Apis mellifera ), which is used as a surrogate for hazard assessment of terrestrial invertebrates, the preliminary risk assessment acknowledged that most registered uses of glufosinate

- ammonium result ed in screening

- level

4 MRID 49135802 Barfknecht (2011 b ), Food acceptance study with rabbits (Oryctolagus cuniculus) and grass treated with Glufosinate

- ammonium SL200. Report No BAR/FS058; Document No. M

- 410867

- 01

- 1

.14 of 21 EECs which were too high to preclude risk at the listed species LOC. The risk assessment also acknowledged data reviews of the European Food Safety Authority (EFSA), which considered potential effects to parasitoid wasp ( Aphidius rho palosiphi ), predatory mite ( Typhlodromus pyri ), wolf spider ( Pardosa s p p.), green lacewing ( Chrysoperla carnea ), ground beetle ( Poecilus
cupreus ), and rove beetle ( Aleochara bilineata ) 5 . A more recent semi

- field study review by EFSA 6 noted that recovery was not observed for all species ( e.g. , predatory mite) within one season, and concluded that the risk for non

- target, non

- Apis arthropods associated with the representative orchard use was high. The Agency’s preliminary risk assessme nt considered these additional lines of evidence qualitatively in characterizing risk to terrestrial invertebrates. The Agency has proposed a new risk assessment process for the honey bee 7 ; future data call

- ins and risk assessments will consider that proc ess as it evolves.

B CS Comment 12 , pages 14

- 15:

“ EPA cites an EFSA document (EFSA 2012) that noted the non [

- ] target arthropod field study did not show recovery.

BCS disagrees with the conclusion drawn by EFSA (2012) that in the non

- target arthropod fie ld study (Bakker, 2004, M

- 235671

- 02

- 1) recovery of the effected species (especially predatory mites) was not demonstrated within one season. Laboratory data demonstrated that predatory mites are the most sensitive group concerning the exposure to glufosina te [

- ] ammonium.

Following two applications of glufosinate [

- ] ammonium, according to the use pattern tested in this study, adverse but transient effects on the non

- target mite community were observed in the treated strip under the trees, but the tree canopy inhabiting populations were not affected. Adversely affected predatory mites (the most sensitive group shown in the laboratory) could clearly be demonstrated during the season from the observed initial effects. ”

EFED Response:

The study described was not submitted to USEPA for review. The summary of the European Food Safety Authority (EFSA 2012) review is referenced for risk characterization in the PRA.

5 European Food Safety Authority (EFSA). 2005. Conclusion regarding the peer review of the pesticide risk assessment of the active substance glufosinate. EFSA Scientific Report 27: 1

- 81. Available online through the EFSA website at http://www.efsa.eu.int

. 6 EFSA. 2012. Conclusion on the peer review of the pesticide risk assessment of confirmatory data submitted for the active substance glufosinate. EFSA Journal 10 (3): 2609. Available online at htt p://www.efsa.europa.eu/en/efsajournal/doc/2609.pdf.
7 US EPA. 2012. White Paper in Support of the Proposed Risk Assessment Process for Bees. Submitted to the FIFRA Scientific Advisory Panel for Review and Comment. September 11

- 14, 2012. Prepared in collaboration with Health Canada Pest Management Regulatory Agency (PMRA) and California Department of Pesticide Regulation. Available online at http://www.regulati ons.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 2012

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- 0004

.15 of 21 B CS Comment 1 3 , page 16:

“ BCS recommends that EPA develop a species sensitivity distribution (SSD) for nontarget terrestrial plants to better characterize potential effects to this taxonomic group. The SSD and an associated defined hazard rate for a specified percent effect on terr estrial plant communities could then be used to discuss potential indirect effects on terrestrial organisms for direct effects on plant communities. ”

EFED Response:

The Agency recognizes the value of species sensitivity distributions (SSDs) and agrees th at such a tool could be useful in characterizing risk to individual species of non

- target plants. However, it is unclear how accurately an SSD for the surrogate crop species tested would reflect actual species sensitivity differences for non

- target, non

- c rop species. The Agency will likely consider the use of SSDs for terrestrial plants as it considers and implements the recommendations of the National Academy of Sciences (NAS) for evaluating risk to listed species. However, in the case of glufosinate

- am monium , such an analysis is not expected to change the conclusion of potential risk to non

- target plants.

B CS Comment 14 , Spray Drift, pages 16

- 17:

“With regards to the calculation of the possible effect distances using AgDRIFT, it is well established t he AgDRIFT overestimates drift, particularly with regards to the ground applications (Jackson, Ledson and Leggett (2012). Drift estimates should be conducted with models that incorporate the data from the Agricultural Agri Food Canada (AAFC)‘2000, ‘2004 an d ‘2011 ( e.g ., Wolf and Cladwell, 2001). This data has been incorporated into the PMRA [Health Canada’s Pest Management Regulatory Agency] drift estimate tool.

BCS would also like to point out the additional information submitted after the problem formulation phase of risk assessment regarding spray drift estimates for glufosinate [

- ] ammonium (Chalmers, A.; Sabbagh, G. (2007) MRID No.: 47381901).”

EFED Response:

With regards to the assertion that AgDRIFT overestimat es drift for ground applications , the assertion is contradicted by the fact that modeled distances to the effect concentration were less than 26 feet, which is well within the distances used by the Spray Drift Task Force to collect deposition data that w ere used to establish the empirica l curves in AgDRIFT. With regards to using the PMRA drift estimate tool as the comment suggest s , the tool employs data from Agricultural Agri Food Canada. EFED has not reviewed the underlying data or methodology used in the development of the tool to eva luate its suitability for use in EPA risk assessments

. EFED will not consider us e of this or any other model or tool in a regulatory decision making
context unless and until it has had an opportunity to conduct a thorough review. No such review of the PM RA drift tool is planned at this time.16 of 21 With regards to the spray drift estimates provided in Chalmers, A.; Sabbagh, G. (2007) MRID No. 47381901, EFED has looked at the study and noted the following: 1. The study evaluated spray drift distance using a number of effect concentrations to 25% of the plants tested ( EC 25 ) . These endpoints rang ed from 0.063 to 0.994 lbs a

. i

. /A

, whereas EFED evaluated spray drift using lower endpoints of 0.062 and 0.018 lbs a

. i

. /A. 2. Spray deposition distances were based on a single application rate of 0.52 lbs a

. i

. /A, while applications for glufosinate

- ammonium range from 0.44 to 1.5 lbs a

. i

. /A.

EFED note s though that for an aerial application at a rate of 0.52 lbs a

. i

. /A (corn, cott on, and soybean seed propagation) and an endpoint of 0.062 lbs a

. i

. /A

, a small er downwind distance (44 feet) to the effect concentration was estimated in the EPA risk assessment than that provided in the cited study (55 feet).

CFS Comment 1, page 5:

“CFS likewise found no consideration given to adverse impacts on the environment that would result from increased prevalence of glufosinate

- and multiple herbicide resistant weeds fostered by post

- emergence glufosinate [

- ammonium] use on glufosinate

- resistant crops; or from increased prevalence of glufosinate

- and multiple herbicide

- resistant crop volunteers acting as weeds.”

EFED Response:

The Agency is aware of one weed species ( i.e
., Italian ryegrass, Lolium multiflorum ) for w hich an introduced trait of glufosinate

- resistance was reported in the United States 8 . Glufosinate

resistance was previously reported in goosegrass ( Eleusine indica ) in Malaysia 9 . Both weed species occur in the United States 10

, 11 and have also demonstrated resistance to the herbicide glyphosate; in general, these species are associated with orchards, other cultivated crops, and landscaped areas.

Consistent with the Overview document 12 , the Agency’s risk assessment for non

- target plants currently focuses on the potential for direct impacts of glufosinate

- ammonium from off

- site transport through runoff or spray drift. From a broad perspective, EFED acknowledges that

8 Heap, I. 2011. The International Survey of Herbicide Resistant Weeds. Available online at www.weedscience.org

. 9 Lee L J & Ngim J

. 2000. A first report of glyphosate

- resistant goosegrass ( Eleusine indica (L) Gaertn) in Malaysia. Pest Management Science

, 56 , 336

- 339
10 U.S. Department of Agriculture (USDA). 2013. Plants profile: Lolium perenne L. ssp. multiflorum (Lam.) Husnot

. Natural Resources Conservation Service (NRCS) National Plant Data Team. Available online at http://plants.usda.gov/core/profile?symbol=lopem2

. 11 U.S. Department of Agriculture (USDA). 2013. Plants profile: Eleusine indica (L.) Gaertn. Natural Resources Conservation Service (NRCS) National Plant Data Team. Available online at http://plants.usda.gov/core/profile?symbol=ELIN3

. 12 U.S. Environmental Protection Agency (USEPA). 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency. Endangered and Threatened Species Effects Determinations. Office of Preve ntion, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. Available online at http://www.epa.gov/oppfead1/endanger/consultation/ecorisk

- overview.pdf.17 of 21 indirect ecological effects may occur through changes in the plant community structure ( e.g ., increased numbers of weeds) as a result of disturbance ( e.g., herbicide application ), and that the nature of these changes is partially dependent upon the relative fitness of surviving or colonizing plant competitors. However, EFED is unaware of any data which demonstrate specifically that glufosinate

- resistant weeds are stronger competitors against native plants than non

- resistant plants within the same weed species or other weed species. More specific to the regulation of glufosinate

- ammonium use, the b est available data do not indicate whether or to what extent glufosinate

- ammonium (regardless of use on glufosinate

- resistant or traditional crops) use may affect non

- target plant species assemblages in adjacent habitat. Therefore, at this time, the quant itative risk assessment will remain limited to an evaluation of (1) the potential for phytotoxicity from non

- target plant exposure

, and (2) indirect effects from direct effects on other species with obligate relationships to plants ( e.g ., pollinators and seed dispersers), based on established LOCs. EFED will characterize the general ecological uncertainties related to glufosinate

- ammonium use on glufosinate

- resistant crops qualitatively in the revised risk assessment, but these uncertai nties will not affect the general risk conclusions because the Agency has already identified risks to non

- target plants.

CFS Comment 2, page s 9 and 10 :
“EPA mentions that glufosinate [

- ammonium] inhibits glutamine synthetase in animals, too (EFED at 6). EPA fails to include the fact that glufosinate [

- ammonium] also inhibits glutamine synthetase in fungi and bacteria, sometimes with lethal results (Ahn 2008, Sanyal and Shrestha 2008, Pampulha et al . 2007, Hsiao et al . 2007). Although pesticide registration reviews do not involve assessing risks to fungi and bacteria specifically (EFED at 9), these taxa interact with plants and animals in ways that are vital to the survival and reproductive success of plants and animals. Therefore, effects of glufosinate [

- am monium] on fungi and bacteria should be taken into account by EPA in the registration review, along with impacts to plants and animals. Also, plant communities are important aspects of habitat for all taxa, and are sensitive to alteration by glufosinate [

- a mmonium] exposure.”

EFED Response:

The Agency is unaware of a method for quantitatively assessing ecological risks resulting from effects on fungi or bacteria. Should appropriate data on glufosinate

- ammonium effects on fungi and bacteria be submitted fo r Agency review, EFED may consider such information in characterizing potential risk in subsequent risk assessments.

CFS Comment 4 , page 11 :
“EPA needs to make a more specific and detailed assessment of the extent to which registered uses of glufosinate [

- ammonium] in the U

. S

. are likely to harm beneficial insects such as predatory mites and spiders, lacewings, and beetles; calling for more species

- specific data, as necessary. If these species that provide pest reduction services are unable to survive and18 of 21 reproduce, it could re sult in crop losses and an increase in use of pesticides, with attendant impacts to the economy, human health and the environment.”

EFED Response:

The preliminary risk assessment identified uncertainties regarding potential risk to listed species of terr estrial invertebrates. Although contact exposure to glufosinate

- ammonium in the laboratory did not cause toxicity to the young adult honey bee, which is used as a surrogate for hazard assessment of terrestrial invertebrates, the preliminary risk assessmen t acknowledged that most registered uses of glufosinate

- ammonium resulted in screening

- level EECs which were too high to preclude risk at the listed species LOC. As noted in a response to a previous comment,
t he risk assessment also acknowledged data revi ews by EFSA, which considered potential effects
to a parasitoid wasp, predatory mite , wolf spider, green lacewing, ground beetle, and rove beetle 13

. A more recent semi

- field study review by EFSA 14 noted that recovery was not observed for all species ( e.g. , predatory mite) within one season, and concluded that the potential risk for non

target, non

- Apis arthropods associated with the representative orchard use was high. The Agency’s preliminary risk assessment considered these additional lines of evidence qu alitatively in characterizing potential risk to terrestrial invertebrates.

CFS Comment 5 , page 12 :
“Given the recent honeybee die

- offs, and the evidence that pesticides are a stressor involved (Mullin et al

. 2010), EPA should include more rigorous testing of glufosinate [

- ammonium] on honeybees in the registration review. In particular, EPA has the flexibility to require studies on toxicity of glufosinate [

- ammonium] to bee larvae, a life stage that is fed poll en and nectar possibly contaminated with glufosinate [

- ammonium] residues, and EPA should call for such studies. Also, field incidents of non

- target injury from herbicides are known to be under

reported, as we discuss below. Field studies designed specifica lly to look at pollinators are thus required to determine whether applications of glufosinate [

- ammonium] have chronic, sublethal, reproductive or behavioral effects, and should be required.

EPA has not considered exposure to glufosinate [

- ammonium] residue s via pollen and nectar in assessing risk to pollinators (EFED at 1, 14, 32

– 33)... In particular, in GE glufosinate

- resistant
crops

– the major use of glufosinate [

- ammonium]

– glufosinate [

- ammonium] and metabolites move extensively, including to flowers and seeds (Ruhland et al. 2004), and some metabolites are stable in the plants, resulting in residues that may be a route of exposure to organisms that consume GE glufosinate

- resistant plant tissues.”

13 European Food Safety Authority (EFSA). 2005. Conclusion regarding the peer review of the pesticide risk assessment of the active substance glufosinate. EFSA Scientific Report 27: 1

- 81. Available online through the EFSA website at http://www.efsa.eu.int

. 14 EFSA. 2012. Conclusion on the peer review of the pesticide risk assessment of confirmatory data submitted for the active substance glufosinate. EFSA Journal 10 (3): 2609. Available online at http://www.efsa.europa.eu/en/efsajournal/doc/2609.pdf.19 of 21 EFED Response:

The Agency notes that pesticides resid ues reported in Mullin et al . 2010 were not specifically linked with honey bee declines; while pesticides have been identified as a factor associated with declines in honey bee health, there are no data that have demonstrated that pesticides are a cause of the these declines. The preliminary risk assessment considers both acute contact and oral toxicity data when describing potential hazard to the honey bee. Specifically, the median lethal dose to 50% of the bees tested ( LD 50 ) value for technical grade gl ufosinate

- ammonium is >100
μg a

. i

. /bee; therefore, glufosinate

- ammonium technical is classified as practically non

- toxic to young adult honey bees on both an acute oral and contact exposure basis. Similarly, the 20.4% a.i. formulation of glufosinate

- ammonium was tested through both contact and oral exposure

, and caused no mortality or sublethal effects at up to the limit dose (LD 50 > 100 μg a

. i

. /bee). The Agency has proposed a new risk assessment process for the honey bee 15

. F uture data call

- ins and risk assessments will consider that process as it evolves

, where additional data will be required for assessing the potential acute and chronic effects of pesticides on adult and larval bees

. However, based on the available data on young adult bees, glufo sinate

- ammonium is classified as practically non

- toxic to bees on an acute exposure basis.

CFS Comment 6 , page s 14

- 16 :
“Herbicide dosage is important for the effects, and sometimes drift levels can stimulate the growth of pathogens, whereas full applic ation rates suppress the same pathogens. Thus non

target plants may be at higher risk for diseases than the treated crop itself from herbicide applications: “It is not unusual for low rates of herbicides to stimulate in vitro pathogen growth (e.g., Yu et a l., 1988). Hormesis (the stimulatory effect of a subtoxic level of a toxin) is common with both fungicide effects on fungi and herbicide effects on plants (Duke et al., 2006). Thus, dose rates are likely to be highly important in both direct and indirect e ffects of herbicides on plant disease.” (Duke et al. 2007).”

“The study by Carpenter and Boutin in 2010 is especially relevant to EPA’s registration review because it focuses on sublethal effects of glufosinate [

- ammonium] at drift levels on a range of wil d and cultivated plants, and includes reproductive responses.

Drift levels can cause sublethal vegetative effects such as necrotic leaves, chlorosis and stunting, and reproductive effects such as flowering delay, deformed flowers, sterility and fewer or smaller seeds (e.g. Davis et al. 2009, Carpenter and Boutin 2010 ). Species vary in their responses and sensitivity. Also, some species can recover from early injuries caused by drift rates of glufosinate, and other species appear to recover but exhibit reproductive abnormalities later (Carpenter and Boutin 2010). In fa ct, in their study of the responses of several crop and wild species to sublethal glufosinate [

- ammonium] applications, Carpenter and Boutin (2010) found that “reproductive outputs” were a more sensitive measure than vegetative injury for more than

15 US EPA. 2 012. White Paper in Support of the Proposed Risk Assessment Process for Bees. Submitted to the FIFRA Scientific Advisory Panel for Review and Comment. September 11

- 14, 2012. Prepared in collaboration with Health Canada Pest Management Regulatory Age ncy (PMRA) and California Department of Pesticide Regulation. Available online at http://www.regulations.gov/#!documentDetail;D=EPA

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.20 of 21 half of the plants tested. They conclude that plants in their natural habitats might be even more sensitive.”

EFED Response:

For each registered herbicide active ingredient (a.i.), including glufosinate

- ammonium , the Agency requires Tier II (concentration

- response) phyotoxicity data on both seedling emergence and vegetative vigor endpoints. The data evaluate the potential effects of both foliar application and root uptake across a range of treatment rates, inclu ding rates below the maximum labeled application rate. Depending on the specific endpoints affected, either the inhibition concentration (IC 25 ) or lethal concentration (LC 25 ) for the most sensitive species is used for risk estimation for non

- listed specie s of terrestrial plants. For listed species of terrestrial plants, the Agency uses the no observed adverse effect level (NOAEL) in risk estimation. Therefore, the preliminary risk assessment (PRA) for glufosinate

- ammonium already considers potential effe cts of exposure to glufosinate

- ammonium at levels below the “full application rate.”

The study by Carpenter and Boutin (2010) 16 will be considered as a n additional line of evidence in the characterization of the potential risk of glufosinate

- ammonium use t o non

- target plants. The data in the Carpenter and Boutin 2010 study are however not suitable for use in quantitative risk estimation because they do not present IC 25 /LC 25 values

, and because the individual data are not available to the Agency. However, as noted by the Center for Food Safety, incorporation of this information is not expected to change the existing PRA’s conclusion of risk to non

- target plants under certain scenarios.

CFS Comment 7 , page 20 :
“In addition to impacts from glufosinate [

- am monium] drift and runoff, we ask that EPA take into account the potential toxicity of glufosinate

- resistant crops, after applications of glufosinate [

- ammonium] , to listed species that might eat corn, soybean, canola and cotton leaves, roots, stems, or flow er parts. Migrating birds, for example, eat parts of the corn plant. Bees consume corn, soybean, canola and cotton pollen; and soybean, canola and cotton nectar, and other insects also utilize pollen, leaves, roots, and other plant parts. Crop detritus was hes into wetlands where it is consumed by aquatic organisms, and is also broken down in soil by detritivores, and may result in different dissipation patterns than those described by EPA (EFED at 23). These crops are planted widely, thus many species are p otentially impacted. Thus the levels and toxicity of glufosinate [

- ammonium] and its metabolites within glufosinate

- resistant plant tissues need to be considered in the complete listed species assessment that is part of this registration review.”

EFED Resp onse:
The residue decline data that were used in this assessment were based on applications to genetically modified ( GMO ) crops carrying the glufosinate

- resistance trait

. The dietary toxicity data used for risk estimation are based on direct treatment of a feed source with a known quantity

16 Carpent er, D., and C. Boutin. 2010. Sublethal effects of the herbicide glufosinate ammonium on crops and wild plants: Short

- term effects compared to vegetative vigor and plant reproduction. Ecotoxicology 19: 1322

– 1336.21 of 21 of glufosinate

- ammonium

. EPA has not received any data which would suggest that toxicity from consumption of GMO crops treated with g lufosinate

- ammonium differ s from consumption of non

- GMO plants treated with glufosinate

- ammonium

.