UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D

. C

. , 20460

PC Code: 112602

DP Barcode: D416981

Date: June 5, 20 14

MEMORANDUM

SUBJECT:



### TO:

FROM: Response to Public Comments on the Trinex apac-eth yl Registration Review

Eco l ogical Risk Assessment

Kaitlin Keller

, Chemical Review Manager

Avi v ah Jakob

, Team Leader

Risk Management and Imp leme ntation Branch III

Pesticide Re-Evaluation Di visio n Offi c e ofPesticide Programs (7508 P )

## ~~u~**os-.JV~** l.0/1 Christopher Koper, M.S.,

### Chemist~ • 

### b**/r/1_~ /.l**  Stephe n Wente

, Ph.D.,

### Biologist~ '1: 

### /J.u,J);(**~ ~** **/'6 G(?** **Y** Meghan Radtke

, Ph.D., Acting RAPL

, 

### . j(__**f'c__~** l Sujatha Sankula

, Ph.D.

, Branch Chief 

## ==-

Env ir onmental Risk Branch I

Enviro nmental Fate and Effects Division (7507P)

Office of Pesticide Programs

In response to the " Registration Review

- Eco logical Risk Assessment and Effects

Determination ofTrinexapac-Ethyl" (DP09748), Syngenta Crop Protection and Crop Life

America su bmitt ed comments during the public comment period. Syngenta submitted 36

individual commen t s addressing the " Registration Review

- Ecological Risk Asse s sment and

Effects Determination ofTrinexapac-Ethyl ", while Crop Life America submitted one comment.
The Syngenta comments were numbered 1 to 36 in the order they appear in th e Syngen ta

comment document (i.e., th ese numbers did not appear in the original document). Comments that

addressed similar topics were combined and summarized to produce a more readable document.
However, the comment numbers were retained to facilitate comparisons with Syngenta's original

comments. Th e single Crop Life America comment appears after the Syngenta ' s comments near the end of thi s document (prior to the Literature Cited and Appendix).

Comments by Syngenta Crop Protection

Syngenta's comments largely addressed conservative assumptions made in the risk asse ssmen t,

conservative assumptions in the models used in the risk assessment

, and how l ess conservative assumptions would h a ve changed the estimatio n of risk in the assessment. Typically

, Syngenta 's2

comments made an argument like: based on less

- conservative assumptions A, B, an d C, the estimated risk for taxa group X would be lower.

The EFED responses address each of the assumptions or other specific issues identified by Syngenta. In Appendix 1, EFED presents amended tables that reflect several changes that were proposed by Syn genta in their comments (Only tables where numbers or text changed are presented. Tables that did not change, and those for which the only change was omitting the unsupported 1.36 lb ai/A application rate, are not included.)

Bare

- ground Terrestrial Field Dissipation Studies

Comment #1 : Syngenta believes non

- linear curve fitting is more appropriate for two bare

- ground field dissipation studies, MRID 48043710 and 48043711 and suggests half

- lives of 1.3 days (parent) and 10.8 days (trinexapac acid degradate)

. ( Syngenta Crop Protection , p. 3 )

EPA Response #1 The Agency agrees that a non

- linear fit is more appropriate than linear in this case and accepts Syngenta’s half

- life values

. EFED is currently developing refined methods for estimating the

formation and decline (half

- lives and formation fractions) of parent and degradates. Therefore because the rate of decline of the parent has to agree with the rate of formation of the degradate,

both of these half

- life values (parent and degradate) may be revisited in t he future. However,

these half

- life estimates would not be expected to radically change. Being a dissipation study rather than a degradation study, t errestrial field dissipation half

- life values are not typically used directly as inputs to models, but rath er compared to input values estimated from degradation studies. The next section concerns the exception to this rule where turf terrestrial field dissipation

half

- lives are used directly as an input to the T

- REX model ( for turf uses only )

.

Turf Foliar Res idue Dissipation

Comment #9 : Syngenta believes that use of the default T

- REX half

- life value of 35 days is overly conservative and does not accurately reflect the environmental fate and potential exposure of trinexapac

- ethyl. Field study data demonstrate the half

- life value for trinexapac

- ethyl on grass is < 1 day (DER for MRID 48043710, DER for MRID 48043711, MRID 41869539, and MRID 41869540). ( Syngenta Crop Protection , p. 5)

EPA Response # 9 : For turf uses (does not include grass grown for seed), the “gr ass total residues” half

- lives calculated using PestDF are 1.96 days for CA (MRID 48043710), 0.386 days for NY ( MRID

48043711 ), 0.245 days for NC ( MRID 41869539 ), and 0.109 days for IL ( MRID 41869540 ).

Therefore the 90 th percentile half

- life estimate is 1. 383 days. EFED will use this value for the T

REX foliar dissipation half

- life of turf scenarios (the default 35

- day foliar dissipation half

- life will be retained for grass grown for seed and other uses) since terrestrial wildlife would be expected to consu me the live plant tissue (grass) rather than thatch ( clippings ).

Environmental Fate

Comment #3 and 5 :3

Syngenta recommended the OR Grass Seed STD scenario as a more representative PRZM crop scenario for modelling grasses grown for seed than the Pennsylvan ia and Florida turf scenarios

used in the risk assessment

. ( Syngenta Crop Protection , p. 4)

EPA Response #3 and 5 : The Agency considered us ing the Oregon Grass Seed scenario along with the Pennsylvania and

Florida turf scenarios to model grasses grown fo r seed . However, the higher amounts of rainfall

in the Pennsylvania and Florida turf scenarios typically result in higher exposures than the Oregon Grass Seed scenario

. U nless the label restricts use to Oregon or to regions more similar to Oregon , the Penn sylvania and Florida turf scenarios will be utilized for a national risk assessment to assess grasses grown for seed.

Residues of Concern

Comment #2 : Based on the environmental fate data for trinexapac

- ethyl, Syngenta believes it would not be possible fo r all of the included degradates to form under typical US soil pHs (pH 6

- 8). Trinexapac

- ethyl hydrolyzes to the free acid (CGA

- 179500) under alkaline conditions (pH 9, t 1/2 = 8.1 days, MRID 41563930). Conversely, the free acid (CGA

- 179500) is stable at bot h neutral and basic pH (MRID 46809301; the major degradation products CGA

- 313458 and an unknown hydrolysis product (M3) were observed only at acidic pH (MRID 46809301). Syngenta believes

the stressor of concern for aquatic exposure should consist of only p arent trinexapac

- ethyl plus the free acid (CGA

- 179500). ( Syngenta Crop Protection , p. 4)

EPA Response #2 : The degradates included in the total toxic residue (parent plus degradates of concern) approach

are based on recommendations from the Residues of Co ncern Knowledgebase Subcommittee (ROCKS) of EPA’s Health Effects Division (HED) (D390121). Only those degradates identified in the abiotic hydrolysis study at pH 7 are included in the total toxic residue abiotic hydrolysis

half

- life (degradates identified at other pHs do not affect this half

- life). Assuming the other fate

studies were conducted under circum

- neutral conditions, all of the total toxic residue half

- lives

are based on circum

- neutral conditions alone.

Turf Application Rates

Comment # 4 , 6, and 7 : Syngenta is amending their turf end

- use product labels (Primo Maxx, EPA Reg. No. 100

- 937; Trinexapac

- ethyl 1ME, EPA Reg. No. 100

- 1401; Lawn Primo G, EPA Reg. No.100

- 930; Lawn Primo F, EPA Reg. No. 100

- 931) to indicate that the single maximum application rate should not exceed 88 fl. oz./A (0.68 lb ai. A). Further, Syngenta will voluntarily cancel the products Primo Liquid, EPA Reg. No. 100

- 729 and Primo WSB, EPA Reg. No. 100

- 752. Syngenta requests that the exposure modelling be updated to reflect the ame nded labelling. ( Syngenta Crop Protection

, p. 4)

EPA Response #4, 6

, and 7 : The relevant amended tables appear in Appendix 1 and include the revised labeling and foliar dissipation half

- life

. There are still acute listed risk concerns for birds for turf use based on 84

app lications at 0.34 lb ai/A with a 4 week reapplication interval and 4 app lications at 0.68 lb ai/A

with a 8 week reapplication interval.

T

- REX Model ing

Comment # 10 : Syngenta notes that the RUD value for arthropods is calculated based on residue values from both field and laboratory studies. RUD values from laboratory studies are typically much higher than those from field experiments (Appendix B of the User’s Guide T

- REX Version 1.5). This difference is attributable to insects being direc tly sprayed with pesticides in laboratory studies, whereas during field applications interception of spray by vegetation occurs. The extrapolated arthropod RUD value of 94 used in TREX v1.5.2 is therefore overly conservative and not

indicative of environme ntally relevant arthropod pesticide residue burdens. Syngenta, therefore; believes that arthropod

- based EECs based for terrestrial vertebrates and invertebrates are likely

overestimated in the current assessment. ( Syngenta Crop Protection , p. 5

- 6)

EPA Res ponse #10 EFED agrees that the data from two laboratory studies, one from the literature and one registrant submitted, present values that appear higher than those of other studies used in the distribution of residues. However, given that the data from so me of the higher end residue measurements from the field do not report variance

, it is not possible to make a definitive call that the laboratory values are completely outside field measurements. Moreover, the rebuttal comment seems to

assume that all inv ertebrates during a spray event will be under cover and avoiding spray th u s precluding the possibility that individual invertebrates would receive the full horizontal or vertical interception of the spray application. EFED is not prepared, in the absence of such data, to adopt that assumption. Therefore, the residue estimates will remain unchanged.

Comment #16: Syngenta believes the modelling (T

- REX) used to assess the risk to birds from consumption of treated granules is overly conservative. Fischer and Best (Environ. Toxicol. and Chem. 11:1495

- 1508., 1995) applied untreated granules to multiple corn fields in Iowa at rates from 3.9 to 17.3 kg/ha. Granules were applied as a banded application. Counts within the band immediately after application averaged 15 granules/ft 2 for every 1 kg/ha applied, or about 6% of the granules applied. Birds representing three taxonomic groups (256 birds total) were collected, and the number of granules consumed was determined by examination of gizzard contents. Nominal appl ication rate had little, if any, effect on the number of granules present in bird gizzards. For the species with the highest consumption rate, the savannah sparrow (Passerculus sandwichensis), median consumption was 11 granules per day, with 95% of individ uals estimated to consume ≤ 23 granules per day. In comparison, based on the highest registered trinexapac

- ethyl (Primo G) granular application; T

- REX calculated the number of granules that would have to be consumed by a small bird (20 g) in order to achie ve the acute listed LOC of 0.1 to be greater than 100. Taking the field data into consideration, Syngenta believes the T

- REX model greatly overestimates the potential consumption of granules by foraging birds. (Syngenta Crop Protection, p. 9)5

E PA Response # 16: As indicated by the rebuttal comment, the Fisher and Best paper involved the application of granules to corn fields. There is considerable bare ground in these environments and EFED can envision that the consumption of pesticide granules might be i nfluenced by the availability of natural grit available in the bare ground areas. There have been past discussion of this data set and its portability across landscapes with different soil and different degrees of cover. Indeed, the Ecological Committee o n FIFRA Risk Assessment Methods (ECOFRAM 1999) presented this very same concept when introducing the Granule Grit Preference facto r which was a product of the availability of granules and the availability of natural grit. The pesticide being reviewed is

ap plied to turf scenarios. There is likely quite a bit of difference between the background amounts of natural grit availa ble for birds in these areas. Therefore EFED is not prepared to assume that the Fisher and Best data represent soil and cover condition s likely encountered in

turf scenarios.

Comment #15: Syngenta notes that deriving RQs for small birds, such as passerine species, based on some food groups is highly conservative and over

- predicts potential exposure. The unlikely occurrence of

small avia n species feeding exclusively on short grass or other solely vegetation

- based diets is

described in the US EPA T

- REX v1.5.2 Manual Section 4.1: Acute and Reproduction Dietary

Discussions

. Therefore, using vegetation

- based EECs values for screening level as sessment to derive RQs estimates may be overly conservative and greater focus should be placed on dietary items that have greater ecological realism for small birds given their feeding preferences (i.e. fruits/pods/seeds and arthropods; Dunn, 2011). (Synge nta Crop Protection, p. 8)

EPA Response #15: EFED agrees. This kind of characterization should be conveyed within a refined risk assessment

. For non

- listed avian species, there are no exceedances of LOCs other than granular 0.88 lbs. ai/A. ( The previous c hronic exceedances for turf were addressed through clarification of the application rates and use of the turf terrestrial field dissipation half

- life as the turf foliar dissipation half

- life.) Therefore, such characterization is unnecessary in the interim decision on

non

- listed species, but will be considered as part of the endangered species assessment.

Avian Data

Comment #1 2 : Syngenta disagrees with the Agency’s interpretation of a zebra finch study (MRID 48894501)

which yielded the most sensitive acute oral endpoint (LD50 = 813 mg a.i/kg

- bw) and the only acute definitive endpoint available for birds

. The study produced an irregular dose response curve with mortalities at the top two treatment levels (2000 and 25000 mg ai/kg

- bw) being lower

than mortalit ies at the second and third treatments levels (500 and 1000 mg/kg

- bw). Therefore

, the Agency calculated a conservative LD50 using just the first three treatment levels (500, 1000, and 1500 mg/kg

- bw). According to Syngenta:

Syngenta believes that all data should be considered in the calculation of an LD50. The endpoint described in the original study report for MRID 48894501 (LD50=1684 mg ai/kg

- bw) is supported by the data. It is also important to note that in addition to the two avian dietary studies with LC50 values >5200 mg/kg

- diet (and no sub

- lethal effects at6

any concentration) described in the current EPA assessment (MRIDs 41563902, 41563903), data are also available for an avian acute oral toxicity study with the mallard duck (MRID 41563901). The avia n acute oral study yielded LD50 values >2000 mg/kg

bw. Dose

- dependent sublethal effects associated with body weight and food consumption were only observed at the highest treatment level (2000 mg/kg

- bw). If requested by the Agency, Syngenta will submit a b obwhite acute oral toxicity study (Campbell et al. 1991) that also supports LD50 values >2000 mg/kg

- bw. Syngenta seeks additional information about the TOXANAL statistical program (2009) that was used to calculate the revised toxicity endpoint (DER for MRI D 48894501) and requests the opportunity to discuss statistical analysis of MRID 48894501 data with the Agency. ( Syngenta Crop Protection

, p. 6)

EPA Response #1 2 : The Agency specifically requests passerine data because passerines have characteristics whi ch may make them more sensitive to pesticide effects. Therefore mallard and bobwhite quail data are of limited value in evaluating passerine data ; however, the Agency will consider all data that

are submitted and potentially could incorporate such data in the refined listed species assessment

or other future assessments

.

Given the non

- monotonic dose response that was observed, the evaluation of MRID 48894501 was conducted in collaboration with EFED’s Terrestrial Biology Technical Team and the

Statistics Te chnical Team. Both teams concurred that the moving average method was an appropriately conservative approach in the estimation of the LD50. EFED welcomes the opportunity to discuss this further with Syngenta

.

Terrestrial Invertebrate s Comment #8 : Syngen ta is submitting with this response a study entitled “Acute toxicity of CGA 163935 tech. to the honeybee Apis mellifera L. Under Laboratory Conditions (Barth 2000)” for Agency review. The study was completed according to OECD 213 and 48

- h oral and contact endpoints were >200 μg ai/bee; confirming that trinexapac

- ethyl is practically non

- toxic to honey bees.

Comment #1 3 : Syngenta believes the LD50 of 47 μg ai/bee reported in the acute contact toxicity study (MRID 41563928) should be recalculated to account for mortality (20%) in the solvent control. The DER for MRID 41563928 calculated LD50 values and accounted for control mortality by using

Abbott’s formula. The resulting LD50 value was 58 μg ai/bee (48.5

- 68.5).

In addition, Syngenta is submitting a new er bee acute toxicity study (Barth 2000) that is of higher quality because it was completed according to the OECD 213 guideline, had no control mortality in the solvent control, and also concurrently tested the reference item, Dimethoate 400 EC. The endpoi nt for the Barth (2000) study was > 200 μg ai/bee as mortality was 3.3 and 16.7% in the 100 and 200 μg ai/bee treatments, respectively.

While control performance was within acceptable limits, the relatively high control mortality in

the solvent control treatment, lack of a positive reference te st, and substantially lower endpoint7

compared to the Barth (2000) study causes Syngenta to question the health of the bee population and/or handling of the bees used in MRID 41563928. Based on trinexapac

- ethyl’s mode of action, there is no reason to believ e that terrestrial invertebrates would be susceptible to exposure; this statement is further supported by lack of sensitivity observed in studies completed with aquatic invertebrates. Taking these factors into consideration, Syngenta believes the Barth (20 00) study represents best available data and should be used in ecological risk assessments

rather than MRID 41563928. ( Syngenta Crop Protection , p. 6

- 7)

Comment #20 and 28 : Syngenta supports the use of a science

- based approach for establishing an appropr iate LOC for

listed terrestrial invertebrates and believes that the interim LOC of 0.05 for all terrestrial invertebrates is overly conservative. ( Syngenta Crop Protection, p. 10 and 12 )

EPA Response # 8

, #1 3

, #20 , and #28 :
EFED is in the process of revie w ing the Barth (2000) study and will update the risk conclusions, accordingly

. In regards to MRID 41563928

, EFED’s policy is to compare the treatment group to the negative control and not to adjust for solvent control mortality. T he T errestrial B iology

T ec hnical T eam is considering the development of a terrestrial invertebrate LOC ; Syngenta is

welcome to submit information that supports a science

- based approach.

Aquatic Plant Study Interpretation

Comment #1 4 : Effect concentrations (ECx) calculated based o n growth rate are considered more robust than those based on standing crop (cell density and biomass) for a given time

- point since growth rate is independent of exposure time

. Moreover, as indicated by Bergtold and Dohmen (2011), the Organization for Econo mic Cooperation and Development (OECD) indicates a clear preference for growth rate as the appropriate endpoint in the Lemna and algal toxicity test guideline (OECD 2006a,b). (Syngenta Crop Protection, p. 7

- 8)

EPA Response #1 4 : The argument provided by S yngenta regarding the transformation of this value to a growth rate is noted and EFED will consider the transformation for this endpoint in future model updates

.

TerrPlant and SIP Modeling

Comment #21 and 35 : Syngenta believes that the runoff assumption s in the TerrPlant model are highly conservative and EECs should instead be estimated by integrating TerrPlant spray drift assumptions with PRZM edge of field (EOF) runoff flux values.

SIP Model ing

Comment #26: Syngenta agrees that use of the water solub ility limit for trinexapac

- ethyl in the SIP model is highly conservative and refinements should be applied. (Syngenta Crop Protection, p. 11)8

EPA Response #21 , #26, and #35 : EFED is currently developing a new terrestrial plant exposure model (Audrey III) that is based on PRZM edge of field estimations to replace the TerrPlant model . However, until th ese new model s ha ve been formally adopted, EFED will continue to rely on the existing models for conducting quantitative exposure assessments for risk to non

- target terrestrial plants.

Risk Calls

Comment #36 : Refinements described in previous comments indicate that potential risks to birds (reptiles and

land

- phase amphibians), terrestrial plants, and terrestrial invertebrates are negligible as screening

level RQs are less than respective LOCs. As such, Syngenta believes the use of trinexapac

- ethyl will not cause either direct or indirect effects to any listed species. Please refer to previous

comments for additional details.

An overview document entitled “Ris k Assessment Considerations Concerning the Potential Impacts of Pesticides on Endangered Species” (MRID No. 49200601), by R. Brain et. al, was submitted August 26, 2013. Syngenta, as the applicant, is available to discuss, with EPA, higher

tier refinements in the trinexapac

- ethyl endangered species assessment.

EPA Response #3 6 : Based on changes to turf application rate s and turf foliar dissipation half

- life, the RQs declined

for these turf uses (see tables in Appendix 1 )

. There are no risks to non

- listed animal taxa. The amended screening

- level assessment still indicates the potential for direct risk concerns to listed birds, reptiles, and land

- phase amphibians, terrestrial invertebrates, and both listed and non

- listed terrestrial plants from the use of tr inexapac

- ethyl on some of its registered use sites. Listed species of all taxa may also be affected through indirect effects because of the potential direct

effects on listed and non

- listed species. Potential direct effect s on listed birds, reptiles, and l and

phase amphibians, terrestrial invertebrates, and terrestrial plants from the use of trinexapac

- ethyl may be associated with modification of primary constituent elements of designated critical habitat, where such designations have been made.

Comments b y Crop Life America

Crop Life America submitted a two

- page document that gave general comments concerning the Registration Review risk assessment process for human health and ecological effects of pesticides. They argue that the risk assessment being don e in the Preliminary Risk Assessment provide only a screening

- level assessment of risk. They argue that these early

- tier assessment generally would not be robust enough for concluding that a pesticide does pose a risk, but rather only indicate when a more refined risk assessment is needed, with additional data to reduce uncertainties. They state that they generally would regard it premature make definitive risk conclusions or to discuss options for risk mitigation based solely on the early

- tier risk

assessm ent. ( Crop Life America , p. 1

- 2 ).

EPA Response: The comments of Crop Life America concerns the general tiered risk assessments process for regulating pesticides within the Registration Review process. The comments were not specific to9

trinexapac

- ethyl , a nd do not address any specific concerns with the trinexapac

- ethyl ecological risk assessment. Therefore, the comments do not suggest any need to change the ecological risk

assessment for trinexapac

- ethyl . EFED defers to the Pesticide Re

- registration Divisi on to respond to the general comments on the tiered risk assessment process.

References

Bergtold, M. and G.P. Dohmen. 2011. Biomass or growth rate endpoint for algae and aquatic plants: Relevance for the aquatic risk assessment of herbicides

Dunn JL. ( 2011). National Geographic Field Guide to the Birds of North America, 6 th Edition. Publisher: National Geographic Society. Pg. 574.

OECD (Organization for Economic Cooperation and Development). 2006b. OECD Guideline 201: Freshwater alga and cyanobacteria, growth inhibition test. Adopted 23 March 2006.

Paris.

OECD (Organization for Economic Cooperation and Development). 2006b. OECD Guideline 221: Lemna sp. growth inhibition test. Adopted 23 March 2006. Paris.

US EPA, 2012. Proposed Methodology for Specify ing Atrazine Levels of Concern for Protection of Plant Communities in Freshwater Ecosystems. Report To: Environmental Fate and Effects Division, Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, DC. EPA/600/R

- 12/019. Mid

- Conti nent Ecology Division,

National Health and Ecological Effects Laboratory, Office of Research and Development,

U.S. Environmental Protection Agency, Duluth, MN. March 5, 2012.10

Appendix 1. Amended Tables from the Trinexapac

- ethyl Registration Review Risk

As sessment

The following tables amend the tables presented in “ Registration Review

– Ecological Risk Assessment and Effects Determination of Trinexapac

- Ethyl ” ( DP 09748 ) . Rather than repeat the entire tables, only the changes to turf uses are presented. Thes e changes were to turf application rates (eliminated the 4 applications at 1.36 lb ai/A with an 8 week reapplication interval use) and and the turf foliar dissipation half

- life (changed from 35 days to 1.383 days). (Note that the Table

number of the table in the PRA that is amended appears at the end of each table caption.)

Estimated Environmental Concentrations

In Table s 1 , 2, and 3

, the reduced turf EECs are presented for birds

, mammals

, and terrestrial

insects , respectively.

Table 1 . Avian trinexapac

- ethyl upper bound EEC values (amends PRA Table 9)

Feeding Category Dietary

based EECs (mg/kg

- food item) Dose

- based EECs (mg/kg

- bw)

Small (20 g) Medium

(100 g) Large

(1000 g)

Turf 8 apps at 0.34 lb ai/A (4 weeks)
Short grass 81.60 92.93 53.00 23.73

Ta ll grass 37.40 42.59 24.29 10.87 Broadleaf plants 45.90 52.28 29.81 13.35 Fruits/pods 5.10 5.81 3.31 1.48 Arthropods 31.96 36.40 20.76 9.29

Seeds 5.10 1.29 0.74 0.33
Turf 4 apps at 0.68 lb ai/A (8 weeks)
Short grass 163.20 185.87 105.99 47.45 Tall g rass 74.80 85.19 48.58 21.75 Broadleaf plants 91.80 104.55 59.62 26.69 Fruits/pods 10.20 11.62 6.62 2.97 Arthropods 63.92 72.80 41.51 18.59

Seeds 10.20 2.58 1.47 0.66

Table 2 . Mammalian trinexapac

- ethyl upper bound EEC values (amends PRA Table 10)

F eeding Category Dietary

based EECs (mg/kg

- food item) Dose

- based EECs (mg/kg

- bw)

Small (15 g) Medium

(135 g) Large

(1000 g)

Turf 8 apps at 0.34 lb ai/A (4 weeks)
Short grass 81.60 77.80 53.77 12.47 Tall grass 37.40 35.66 24.64 5.7111

F eeding Category Dietary

based EECs (mg/kg

- food item) Dose

- based EECs (mg/kg

- bw)

Small (15 g) Medium

(135 g) Large

(1000 g)

Broadleaf plants 4 5.90 43.76 30.25 7.01 Fruits/pods 5.10 4.86 3.36 0.78 Arthropods 31.96 30.47 21.06 4.88

Seeds 5.10 1.08 0.75 0.17
Turf 4 apps at 0.68 lb ai/A (8 weeks)
Short grass 163.20 155.60 107.54 24.93 Tall grass 74.80 71.32 49.29 11.43 Broadleaf plants 91.80 87.52 60.49 14.03 Fruits/pods 10.20 9.72 6.72 1.56 Arthropods 63.92 60.94 42.12 9.77

Seeds 10.20 2.16 1.49 0.35

Table 3 . Adult insect foliar spray upper

- bound EEC values (amends PRA Table 11)

Use EEC (based on tall grass) (mg/kg

- diet) (dose in μg ai/ bee*) EEC (based on

arthropod) (mg/kg

- diet) (dose in μg ai/bee**) 1

Turf 8 apps at 0.34 lb ai/A (4 weeks) 37.40 ( 10.92 ) 31.96 (4.09)

Turf 4 apps at 0.68 lb ai/A (8 weeks) 74.80 ( 21.84 ) 63.92 (8.18)

*Conversion made by multiplying EEC by food consumption rate of adult bee (0.292 g/day) **Conversion made by multiplying EEC by body weight of adult bee (0.128 g)

1 Based on single app at the highest single application rate if application interval is >5 days

Risk Quotients Tables 4, 5, and 6 present the reduc ed risk quotients for turf uses for birds, mammals, and terrestrial insects, respectively. For birds, risks still remain for su garcane, grasses grown for seed,

an d both modeled turf application rates. It would be prudent to consider Syngenta’s comment:

Sy ngenta notes that deriving RQs for small birds, such as passerine species, based on some food groups is highly conservative and over

- predicts potential exposure. The unlikely occurrence of small avian species feeding exclusively on short grass or other

sol ely vegetation

- based diets is described in the US EPA T

- REX v1.5.2 Manual Section 4.1: Acute and Reproduction Dietary Discussions. Therefore, using vegetation

- based EECs values for screening level assessment to derive RQs estimates may be overly

conservati ve and greater focus should be placed on dietary items that have greater12

ecological realism for small birds given their feeding preferences (i.e. fruits/pods/seeds and arthropods; Dunn, 2011). (Syngenta Crop Protection, p. 8)

All of the RQ exceedances for listed birds (no non

- listed LOC exceedances) are for “ short grass or other solely vegetation

- based diets ”.

Table 4 . Upper bound risk quotients for birds derived from T

- REX (amends PRA Table 20)

Risk Quotients

Based on Kenaga Upper Bound EEC Dose

- Based R Qs Chronic Dietary

Based RQs 20 g 100 g 1000 g

Acute Acute Acute

Turf 8 apps at 0.34 lb ai/A (4 weeks)
Short grass 0.11* 0.05 0.01 0.41 Tall grass 0.05 0.02 0.01 0.19 Broadleaf plants 0.06 0.03 0.01 0.23 Fruits/pods 0.01 0.00 0.00 0.03 Arthropo ds 0.04 0.02 0.01 0.16

Seeds 0.00 0.00 0.00 0.03
Turf 4 apps at 0.68 lb ai/A (8 weeks)
Short grass 0.21* 0.09 0.03 0.82 Tall grass 0.10* 0.04 0.01 0.37 Broadleaf plants 0.12* 0.05 0.02 0.46 Fruits/pods 0.01 0.01 <0.01 0.05 Arthropods 0.08 0.04 0.01 0.32

Seeds <0.01 <0.01 <0.01 0.05

Bold text indicates an LOC was exceeded. * Exceeds the acute listed species LOC of 0.1

**Exceeds or meets the acute non

- listed species LOC of 0.5

***Exceeds the chronic LOC of 1

There were no exceedances for mammals be fore these changes and are none after the changes

either.

Table 5 . Dietary upper bound risk quotients for mammals (amends PRA Table 21)

Risk Quotients

Based on Kenaga Upper Bound EEC Dose

- Based RQs Chronic Dietary

Based RQs 15 g 35 g 1000 g

Acute Ch ronic Acute Chronic Acute Chronic

Turf 8 apps at 0.34 lb ai/A (4 weeks)
Short grass 0.01 0.06 0.01 0.05 <0.01 0.03 0.0113

Risk Quotients

Based on Kenaga Upper Bound EEC Dose

- Based RQs Chronic Dietary

Based RQs 15 g 35 g 1000 g

Acute Ch ronic Acute Chronic Acute Chronic

Tall grass <0.01 0.03 <0.01 0.02 <0.01 0.01 <0.01 Broadleaf plants <0.01 0.03 <0.01 0.03 <0.01 0.02 <0.01 Fruits/pods <0.01 <0.01 <0.01 0.00 <0.01 <0.01 <0.01 Arthropods <0.01 0.02 <0.01 0.02 <0.01 0.01 <0.01

Seeds <0.01 <0.01 <0.01 0.00 <0.01 <0.01 <0.01
Turf 4 apps at 0.68 lb ai/A (8 weeks)
Short grass 0.02 0.12 0.01 0.10 0.01 0.05 0.01 Tall grass 0.01 0.05 0.01 0.05 <0.01 0.0 3 0.01 Broadleaf plants 0.01 0.07 0.01 0.06 <0.01 0.03 0.01 Fruits/pods <0.01 0.01 <0.01 0.01 <0.01 <0.01 <0.01 Arthropods 0.01 0.05 0.01 0.04 <0.01 0.02 0.01

Seeds <0.01 <0.01 <0.01 <0.01 <0.01 0.00 <0.01

The adult insect foliar spray risk s (listed species only) still exist for sugarcane, grasses grown for seed, and both modeled turf application rates.

Table 6 . Adult insect foliar spray risk quotient values (amends PRA Table 23)

Use RQ

Turf 8 apps at 0.34 lb ai/A (4 weeks) 0.09*

Turf 4 apps at 0. 68 lb ai/A (8 weeks) 0.17*

*Exceeds the listed species interim LOC of 0.05

Table 7 updates the o dds of mortality for a bird or terrestrial invertebrate f rom trinexapac

- ethyl applications.

Table 7 . Odds of mortality for a bird or terrestrial invertebra te for trinexapac

- ethyl (amends PRA Table 28)

RQ Slope 95% Confidence

Interval Odds

(1 in...)

Birds (turf at 0.34 lb ai/A) 0. 11 4.5 2, 9 1.25E+05

Birds (turf at 0.68 lb ai/A) 0. 2 1 4.5 2, 9 874

Terrestrial invertebrates (turf at 0.34 lb ai/A) 0.09 2.43 1 .77, 3.09 181

Terrestrial invertebrates (turf 0.68 lb ai/A) 0.17 2.43 1.77, 3.09 3314

Table 8 presents the distance from a treated field (buffer distances) in which LOC exceedances would be expected. Oddly the aerial applications (sugarcane and grasses gr own for seed) produce 0 ft buffers, while ground applications (sugarcane, grasses grown for seed, and both modeled turf application rates) produce 3.82 ft buffer distances. It appears that AgDRIFT rounds to the nearest meter and then converts to English un its ( 1 meter = 3.28 ft ). It is likely that both the aerial and ground buffer predictions are small distances with the aerial buffer being less than 0.5 meter (rounding to 0) and ground buffers being between 0.5 and 1.5 meters (rounding to 1 meter or

3.28 f t).

Table 8 . Avian, reptile, and terrestrial

- phase amphibian Buffers for trinexapac

- ethyl

calculated with AgDRIFT (amends PRA Table 29)

Use Single A pplication Rate (lb ai/A) Fraction of Applied Buffer Distance (ft)

Turf (ground) 0.34 0.67 3.28 * Turf (g round) 0.68 0. 48 3.28 *
* AgDRIFT appears to default to 3.28 ft (1 meter) for ground applications producing small buffer distances. Possibly AgDRIFT rounds to the nearest meter before converting to English units.

Table 9 summarizes risks to listed species for the amended turf scenarios. Again there are no

non

- listed exceedances for birds.

Table 9. Trinexapac

- ethyl uses that exceeded the acute dose

- based listed LOC (0.1) for

birds (amends PRA Table 30)

Use Dose

- based RQs

Short grass Tall grass Broadleaf plants Arthropods 20 g 100 g 1000 g 20 g 100 g 1000 g 20 g 100 g 1000 g 20 g 100 g 1000 g
Turf (0.34 lb ai/A) Yes No No No No No No No No No No No Turf (0.68 lb ai/A) Yes No No Yes No No Yes No No No No No

In Table 10 the buffer distances are for li sted terrestrial invertebrates only (no non

- listed LOC exceedances for terrestrial invertebrates).

Table 10 . Terrestrial invertebrate buffers for trinexapac

- ethyl calculated with AgDRIFT (amends PRA Table 31)

Use Single A pplication Rate (lb ai/A) Fractio n of Applied Buffer Distance (ft)

Turf (ground) 0.34 0.56 6.56 Turf (ground) 0.68 0.29 9.84

Tables 11 and 12 summarize the exceedances of listed and non

- listed LOCs. Non

- listed monocots exceed for only turf applications at 0.68 lb ai/A, while non

- listed dicots only exceed for grasses grown for seed and turf applications at 0.68 lb ai/A. Both listed monocots and listed

dicots exceed for all uses

.Table 11 . Trinexapac

- ethyl application scenarios that exceeded the LOC for listed and non

- listed mono cots (amends PRA

Table 32)

Use Non

- listed monocot Listed monocot Dry Semi

- aquatic Spray drift Dry Semi

- aquatic Spray drift

Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem

Turf (0. 34 lb ai/A0 No No No No No No No No Yes Yes No No Turf (0.68 lb ai/A) No No Yes Yes No No No No Yes Yes No No

Table 12 . Trinexapac

- ethyl application scenarios that exceeded the LOC for listed and non

- listed dicots (amends PRA Table 33)

Use Non

- listed d icot Listed dicot Dry Semi

- aquatic Spray drift Dry Semi

- aquatic Spray drift

Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem Ground Aerial/

Chem

Turf (0.34 lb ai/A0 No No No No No No No No Yes Yes No No Turf (0.68 lb ai/A) No No Yes Yes No No No No Yes Yes No No