UNIT E D STAT E S E N V IRONMENTAL PR O TE C TION AGENCY
WASHINGTON

, D

. C

. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUT I ON PREVENTION

ME MORAND U M

D A T E :

SU BJ ECT:

T O:

FRO M : June 9, 2015

Re spo nse to Public Comments on the Pr e lim i nary Environmental Fate and Eco logical Risk Assessment for the Registration Review of Sulfentrazone ( P C C od e N o

. 129081 ; DP B a r co d e D40 9 753 )

Christina Scheltema, Chemical Review Manager Patricia Parrott

, Branch Chief Risk Management and Implement at ion Branch 3 Pesticide Re-evaluation D i v ision (7508 P )

Geoffrey Sinclair, PhD

, Biologist**~ ~** **~** Michael Barrett

, PhD

, Chemist f.../V t ( ' '-....../**~U** Enviro nmental Risk Branch V E nvironmental Fate and Effects Division (7507C)

THRO UG H: Mah T. Sham i m, P h.D., Chief Environmenta l R i sk Branc h V Envi r onmenta l Fate and Effects Division (7507C)

E PA r eceived comments in response to the " Pr e liminar y E 11 v ir o 11m e 11tal Fat e and Eco l og i c al R is k Assess m e nt f o r til e R eg i s tration R ev i ew of S 11 /f e 11tra zo 11 e" (Document ID EPA-HQ-OP P

2009-0624

- 00 17 in www.regulations.Q.ov ) (DP Barcode: D409753. dated June 11, 2014) from FMC corporation during the public comment period. The pu r pose of this memorandum is to address those comments. The E n vironmenta l Fate and Effects Division (EFED) used an outlinetype of format to address the comments. The comments taken from the FMC submission are presented in italics and EFED responses to those comments follow in an i ndented paragraph. EFED·s purpose of the document is to respond to technical/science-related questions and

comments.

12 FMC Comment 1: T he conclusion of the second paragraph on page two infers that sulfentrazone is expected to move to surface water and groundwater but does not actually characterize the likelihood of potential movement. Characterization of potential movement should consider influential factors beyond Koc, such as: 1) sulfentrazone mobility and persistence under field conditions using the recommended and relevant rates and method of application and 2) spatial variations of soil characteristics that are linked to sulfentrazone behavior and maximum allowable applic ation rates.

EFED agrees with the registrant’s comments regarding the factors that can be important in determining the ultimate fate of sulfentrazone from site to site. The available Prospective Ground Water ( PGW ) studies show that leaching of sulfentrazo ne residues occurs at all four different study sites with a variety of characteristics

. Sulfentrazone is sufficiently persistent and mobile to leach at some measurable amount at a variety of locations but the actual amount of mass transport into subsurface horizons will be highly dependent on the amount and timing of precipitation or irrigation events after application as well as the site characteristics and specific fate properties of sulfentrazone ob served at a site. The level of overall impact on groundwater will also be dependent on what the long

- term use pattern for sulfentrazone is in areas that constitute the recharge area for the aquifer. Further delineation of areas where sulfentrazone may impa ct groundwater after its use is not practical with the available assessment information and tools.

FMC Comment 2: The conclusion of this paragraph indicates that screening

- level non

- target plant modeling results in potential risk to plants adjacent to u se areas; however, potential risk should be evaluated using best

- available data and refined risk assessment methods. The revised, final ecological assessment should include best available data and refinement and data before concluding potential for adverse effects to listed species.

EPA ’s preliminary risk assessments are based on screening

- level non

- target plant modeling using studies submitted to the agency and agency reviewed literature. Based on this preliminary assessment, and refinements using the standard EFED AgDrift model the assessment identified risk to plants in adjacent use areas and attempted to characterize the effects distances needed to reduce risk

. Refinements included changing boom height and median droplet s izes to assess impact of application methodology. Subsequent to the public comment period, the Agency incorporated additional refinements into the risk
assessment.

EPA is currently working with its federal counterparts and other stakeholders to implement an interim approach for assessing potential risk to listed species and their designated critical habitats. Once the scientific method ology for risk assessments for listed species and their designated critical habitats are finalized, the Agency will compl ete its endangered species assessment for sulfentrazone. FMC Comment 3: Marine/estuarine biota are not expected to be exposed to significant concentrations of sulfentrazone as once the herbicide enters the systems it is expected to be diluted well beyond the standard EPA ‘pond’ that is simulated (Table 23 of preliminary risk3 assessment). The standard EPA pond scenario does not physically represent marine/estuarine systems. FMC suggests that the RQ generated for marine/estuarine species, which is not deriv ed from measured data, be revised to be reported in a format that reflects exposure uncertainty due to the considerable dilution potential difference between the standard EPA pond and marine/estuarine systems. Refer to additional FMC comments for further d iscussion and information regarding the aquatic risk assessment. The standardization of avian risk is a useful tool to indicate potential risk, but further revision to the draft assessment should be done to address the chemical

- specific expected exposure e stimate and conservative consumption assumptions that apply to sulfentrazone.

Risk Quotients are based on actual measured toxicity endpoint points or endpoints derived through acute

- to

- chronic ratios (ACRs) where data do not exist as is indicated in the preliminary risk assessment. Standard EPA models are used to generate estimated environmental concentrations that estuarine/marine organisms may be exposed to. Until other models are vetted and adopted, these models will be used i n current and future risk assessments. The toxicity endpoints are compared to estimated environmental concentrations for both freshwater and estuarine/marine environments from modeling runs that are standard in all preliminary risk assessments. The chroni c endpoint for the saltwater mysid was not available so an ACR was used in lieu of this endpoint , in accordance with EPA policy. Use of an ACR is accompanied by uncertainty , which characterized in the ecological risk assessment addendum for sulfentrazone

. Additionally, the risk assessment addendum includes further description of avian risk and upper bound versus mean estimates of exposure through consumption of dietary items.

FMC Comment 4: EPA policy accounts for enhanced toxicity of LDPH chemicals to animals under UV radiation. In this case, habitat/water containing aquatic organisms is assumed to be clear or transparent so that the light could penetrate through the water and create a condition for enhanced toxicity. The EPA statement appears to indica te that worst

- case UV conditions (light

- penetrating aquatic systems) are the standard for assessing uncertainty in surface water toxicity. It follows that aquatic exposure estimation of sulfentrazone should also include this assumption of UV conditions, i. e. relatively clear water systems

– as opposed to assuming turbid water environments, as is currently done. Modeling aquatic exposure as ‘turbid’ appears to be inconsistent with this policy.

Since photolysis was important to the degradation rate of sulfen trazone in aqu atic systems , the best

- and worse

- case scenarios as dictated by turbidity (high and low light environments) were presented (Table s 23 and 24 in the preliminary risk assessment) . In the case of fish (Table 23)

, incorporating the LDPH factor in both scenario s did not change the risk picture. It is noted that t he majority of water bodies surrounding agricultural areas will

, however

, be turbid waters with low photolysis rates. M odeling only clear water colu mns where LDPH would be of greater co ncern would not be representative of most agricultural systems but was described to bound the risk to fish in different light environments in aquatic systems

.

FMC Comment 5: EPA’s use of the AgDrift model combined with the lowest observed ecological e ndpoint provides overly conservative estimates for typical sulfentrazone use4 environments. It is suggested that the EPA consider alternative drift models and revised endpoint selection.

The EPA acknowledges the utility for alternative drift models but doe s not currently employ those models as they are undergoing the QA/QC process and are not appropriate for risk assessment purposes . The current AgDrift model combined with observed ecological endpoint is the standard method for screening level risk assessments

. However, EPA has re

- reviewed the vegetative vigor data and recalculated this endpoint using the CETIS software. The new endpoint is now 0.0016 lbs ai/A instead of the previous endpoint of 0.0005 lbs a.i./A. For more detail s, see the assessme nt addendum and the revised data evaluation record associated with this study.

FMC Comment 6: Sulfentrazone is a pre

- emergence herbicide that is typically applied to the soil before planting or prior to crop emergence. Over 99% of sulfentrazone is applied by low boom ground applications (GFK data software, 2013) to provide maximum soil coverage. Additional refinement to surface water and non

- target plant modeling should consider aerial and high

- boom applications independently from ground application becaus e aerial/high

- boom application scenarios are rare.

The role of the environmental and ecological assessment is to cover all possible uses. The preliminary risk assessment presents modeling results for low boom and coarse droplet applications as well as those for high boom and a erial application (see Tables 32 and 33 )

. During risk description

, it is possible to qualitatively describe that the majority of the applications are applied with low boom and coarse droplet applications. The risk assessment adde ndum describes in more detail the refinements that were performed using information provided by the Biological and Economic Analysis Division with an emphasis on low boom applications and coarse droplet sizes

.

FMC Comment 7: This table considers spray dri ft alone and does not consider the refinement needed for runoff to dry and semi

- aquatic areas in the TerrPlant model. Incorporating mitigation from spray drift buffers to address a potential concern that includes spray drift and runoff combined does not represent a complete assessment and should be revised. As mentioned, more current spray drift data is available for use in identifying potential risk in tools such as RegDISP. Once exposure from drift has been characterized using more current tools/data, t he exposure from runoff contribution to dry and semi

- aquatic areas should also be revised.

TerrPlant and AgDrift are the current model s being used by E PA to assess off

- site transport of the active ingredient to adjacent plant populations. The Agency is n ot currently able to use alternative tools

, such as R egDISP

, in a direct fashion for risk
assessments

. M odels such as AgDISP are currently under going internal Agency review and validation and may be incorporated into future assessments.

FMC Comment 8: Sulfentrazone is a pre

- emergence herbicide that is typically applied to the soil prior to planting or before crop emergence. As sulfentrazone is predominantly used as a pre

emergent herbicide, efficacy depends on soil coverage rather than leaf contact. To maximize soil coverage, spray nozzles that provide medium/coarse droplet size are desirable, as indicated on5 the federal label. It is impractical and extremely unlikely for a grower to use a fine spray droplet size if the product is to be used in complian ce with the label and current agronomic practices. Medium

- very coarse droplets are desirable for growers for soil

- applied herbicide control of pre

emergent weeds. All federal labels for sulfentrazone recommend nozzles that produce minimal amounts of fine s pray droplets to avoid spray drift for both ground and aerial application. In addition, labels indicate that a fine spray should be avoided and that maximum soil/plant coverage should be targeted

– avoiding spray drift beyond the area intended for treatmen t.

Fine to coarse droplet sizes were modeled to provide a range of impacts. Clearly coarse droplet sizes would decrease the extent of transport relative to fine droplet sizes. The assessment discusses the impact of each. We appreciate that it is imprac tical and extremely unlikely for a grower to use a fine spray droplet size if the product is to be used in compliance with the label and current agronomic practices. However, because not all labels were clear with regard to droplet size and because the cu rrent spray drift labeling is, in many cases, advisory rather than mandatory, EPA model ed all possible spray drift scenarios , including fine droplet size. For sulfentrazone as a pre

- emergent application, EPA acknowledges that application through coarse droplet sizes is preferred to enhance soil delivery and minimize off

- field drift.

FMC Comment 9: FMC understands that the Agencies (EPA, FWS, NMFS, and USD A) are coordinating efforts to further refine their approach to conducting ecological risk assessments in support of listed species effects determinations. FMC will provide any data needed to conduct refinements that include more detailed analyses of regis tered uses and specific use patterns. FMC is member of the FIFRA Endangered Species Task Force (FESTF) that has tools that can provide these refinements. Procedurally, for effects determination evaluation for individual listed species, FMC/ FESTF would wo rk with the Agencies to provide additional details on spatial use patterns, sub

- county spatial proximity data for co

- occurrence of potential effects areas and listed species and designated critical habitat. FMC understands that the Agencies are coordinatin g efforts to further refine this screening level assessment to support listed species effects determinations.

EPA appreciates that FMC will work with Agencies to provide additional details on spatial use patterns, sub

- county spatial proximity data for co

- occurrence of potential effects areas and listed species and designated critical habitat.

FMC Comment 10: The Agencies’ characterization of ‘broad potential for direct adverse effects to listed and non

listed species of aquatic and terrestrial plants’ has not been evaluated in the preliminary assessment. Further refinement of the preliminary risk assessment is necessary to accurately represent the risk to non

- target organisms.

The use of the word broad refers the sulfentrazone’s ability to adversely affect listed and nonlisted plants from all three of the modeled exposure scenarios (spray drift only, runoff and spray drift (dry areas) and runoff and spray drift (semi

- aquatic are as). The capability of adversely affecting plants in these assessments constitutes a broad potential to adversely affect plants as would be expected from a herbicide. The assertion that “this6 preliminary assessment would not qualify as characterizing bro ad potential for adverse effects for the following reasons” lists reasons that pertain to how the EPA performs preliminary risk assessments. As stated earlier, the assessment utilized the models that are standard in preliminary risk assessments. The Agenc y agrees assumptions such as 100% PCA are highly conservative for most ecological exposure scenarios but believes that, if the product is used at maximum label rates, the conclusions could apply to organisms living in or around water bodies with very small drainage areas. EPA performed additional analysis that are described in the addendum to consider additional exposure scenarios that increase droplet sizes and decrease boom heights.

This preliminary assessment would not qualify as characterizing broad p otential for adverse effects for the following reasons:

• Tier 1/Screening

- level modeling for terrestrial plants: o Single

- species effect endpoint exclusively used (monocot and dicot), i.e. no consideration of community

- level effect or ecologic relevanc e of potential effect

. As part of the preliminary risk assessment process, EPA does not model community level effects

. The single species endpoint is the standard way in which the A gency assesses risk to non

- target plants

. o Use of AgDRIFT provides inadequate and outdated spray drift exposure estimation techniques/modeling. More current and representative spray drift information is publically available (e.g. RegDISP) and should be utilized.

AgDrift is currently the standa rd model used in the preliminary risk assessment process. Other models , such as RegDISP, are currently under going internal Agency review and validation and may be incorporated into future assessments.

o Aerial application method should be limited to appr opriate crop/uses and small

- scale geographies that represent 1% of all application methods. Ground application under a low boom application type should be the application method assessed broadly across the majority of crops and should consider rate restric tions around soil

.

E PA appreciates that the predominant application method is ground application using coarse droplet size from a low boom. However, because some sulfentrazone labels list aerial application, Agency modeled all scenarios for completeness sake. The risk assessment addendum focused on applications with low boom height and coarser droplet sizes as well as specific application rates associated with aerial applications

. It is understood that aerial applications generally only occu r when fields are too wet to all access by ground equipment.

o No refinement of runoff contribution to terrestrial (dry and semi

- aquatic) systems, 5% runoff assumed for all crop growing areas o No spatial co

- occurrence analysis of semi

- aquatic (wetland) habitat and adjacent use areas7 o Assumptions of application at the maximum application rate, % crop treated and registrations at the state level are not included in the assessment o Spatial and temporal co

- occurrence, frequency, and likelihood of effects based on labeled rates and associated soil restrictions are not evaluated

• Tier 1/Screening

- level modeling of aquatic plants: o Aquatic exposure is based only on a highly conservative, single combination of soil and weather conditions per crop and region. A much broader range of soil and weather conditions are relevant for each crop and should be considered in a refined assessment before judgments on the extent of any potential effects can be determined o The assumption of 100% PCA for all crop scenarios is a highly conservative extreme case. Spatial analysis of small pond wate rsheds shows that PCAs are typically much less than 100%, with a case study of ponds in California showing median PCAs of approximately 12% (Winchell et al., 2014)

The comments concerning more detail ed spatial analysis associated with the assessment

are noted. At this time, such an analysis is beyond the scope of a tier 1 preliminary assessment. There are spatial models such as a Spatial Aquatic Model (SAM) being developed that will help address these comments and help refine risk assessments and evalua te risk to endangered species in the future

.

FMC Comment 11: FMC recommends the risk assessment to non

- target plant toxicity follow the EPA’s proposal that provides the impetus for defining effect at the 25th percentile as outlined in an EPA SAP panel br iefing (Davy, et. al. 2001). Michael Davy, et al. 2001. Scientific Advisory Panel Briefing. Proposal to update non

- target plant toxicity testing under NAFTA. Joint EPA/PMRA document. http://www.epa.gov/oscpmont/sap/meetings/2001/june/sap14.pdf

. FMC recommends the use of the EC50 value to be consistent with the other effect metrics for all other risk categories and as a more meaningful effect metric because:

• The EC25 appears to be related to a cosmetic

- level effect (protection goal) for high

- value ornamentals and fruits and is not intended to cover terrestrial plants in natural ecosystems • Endpoints measur ed to determine risk corresponding to the EC25 (e.g. dry weight) are not linked to fundamental plant productivity metrics, such as flower formation, pollen or seed viability, etc • A tiered approach is recommended in which non

- target terrestrial plants th at are relevant to natural ecosystems would require a higher tier of assessment to determine adverse effects • Using the EC25 from surrogate plants with no correlation to natural plants does not characterize risk In addition to the issue of applying an a ppropriate effect endpoint from surrogate data, a correction should be made to the actual calculation of the EC25 for cucumber. The EC25 calculation for cucumber (dry weight endpoint) was re

- evaluated and upon confirming normality in the raw data, Probit A nalysis was conducted using the original data (MRID 43345412) according to current standards. The resulting EC25 value was determined to be 0.00275 lb ai/A. Additionally, the EC50 value was also calculated as 0.00514 lb/ac (Standard error: 0.0003059).8 The corrected EC25 value of 0.00275 lb ai/A should be used in the risk assessment in lieu of the previously

- calculated EC25 of 0.00052.

The EPA appreciates the value of alternate methods to risk assessment. EPA

, however

, has an established protocol for asses sment of risk to non

- target plants. The vegetative vigor data for sulfentrazone ( MRID 43345412 ) has been reevaluated using updated CETIS software. The EPA concurs that the previous endpoint for vegetative vigor in the cucumber was incorrectly calculated. The new EC25 endpoint, presented in more detail in the addendum

, was determined to be 0.0016 lb ai/A. This endpoint was used to refine both TERRPLANT modeling to generate RQs as well as in AgDrift modeling to generate effects distances

.

FMC Comment 12: Residue data for registered crops shows that plants do not uptake sulfentrazone residue from soil (pre

- plant) and translocate (redistribute) it into the foliage and above

- ground portion of the plant/crop. It is important to note the distinc tion between ‘systemic’ and the process of plant uptake of sulfentrazone through the root zone and via translocation. This distinction is important because it affects the potential sulfentrazone exposure to terrestrial organisms via plant tissue. Kenaga no mograms (page 46, Table 15) used within this preliminary risk assessment represent maximum dietary/plant residues and therefore overestimate risk to terrestrial organisms. FMC suggests that this information be considered and incorporated into the final ris k assessment on a qualitative not quantitative basis.

E PA appreciates insight as to the difference betwe en systemic uptake and translocation. The T

- REX model is the standard model with which to assess risk to terrestrial animals in preliminary risk assessments. Further it is EPA policy to use the upper bound Kenega nomograms in risk characterization as they are the most pro tective

, while the mean Kenaga nomograms may be used to describe risk in more detail. Additional analysis of avian risk was conducted by examining multiple application rates as well as compari ng upper bound and mean K enaga values and the amount of time that residues are expected to be of concern.

FMC Comment 13: The label restriction “ Do not use on coarse soils classified as sand which have less than 1% organic matter.” is required on all sulfentrazone labels. The sizeable exclusion of soils that mee ts this criteria, as well as rate limitations corresponding to soil texture as outlined in Table 2, should be a significant element of characterizing potential risk to non

target organisms and has not been applied in the preliminary assessment. The action area represented by conservative Tier I modeling used in the preliminary assessment likely represents a small and improbable use area, the exact spatial extent of which has not been quantified. Geospatial consideration of sulfentrazone rate limitations sho uld be incorporated in the refined assessment. Mitigation or risk conclusions that ignore critical label language on the federal label disparages and undervalues past science and policy that were implemented to proactively and responsibly protect ecosystem integrity.

EPA believes that the label restriction regarding coarse low organic matter soils prevents usage on some of the most vulnerable sites for sulfentrazone leaching (we are assuming the registrant’s comments mostly have in mind potential for sulfentrazone residues to9 impact groundwater) , but this restriction does not include large areas where there is a finite leaching potential for sulfentrazone. Therefore, this lab el restriction does not alleviate the need for mitigation measures in areas where sulfentrazone can still be used. E PA agrees that, should a more refined risk assessment become necessary in the future, consideration of spatial variability in soils, hydroge ology, weather, and agronomic practices and of the degree of alignment of the most vulnerable areas with existing or potential use areas for sulfentrazone products would be appropriate

.

FMC Comment 14: Page 18, row 3 & 4: Corn is listed twice. The correc t corn minimum single application rate (column 2) is 0.09 lb ai/A and the correct maximum single application rate is 0.25 lb ai/A. P age 19, row 2, column 2: The correct minimum single application rate for melons is 0.09 lb ai/A. Page 19, row 6/Page 20, ro w 9: Soybeans are listed twice. Soybeans should be removed from the reference on page 19 since row 6 is incorrect. Page 21, footnote: The maximum annual use rate is 0.375 lb ai/A for turf (sod production, lawns, golf fairways and roughs).

EPA will incorporate this information in a m emorandum updating the assessment.

FMC Comment 15: FMC suggests that alfalfa, pumpkins, rice, winter wheat and spring wheat outside of the Pacific Northwest should not be included in the risk assessment. Neither a federal registration nor a tolerance are established for use on alfalfa, pumpkins or rice (rotational tolerance only). Wheat is limited to a regional registration/tolerance in the Pacific Northwest and only on the spring wheat variety. The qualitative implications related to the average and maximum percent crop treated data (ranges from <1% to 50%) suggest that sulfentrazone is being applied to a relatively small actual acreage for any given crop. This relatively small acreage has less likelihood of co

- occurrence with sensitive species, compared to 100% percent crop treated. This information could be translated into the risk assessment, paired with the lack of incident reports since 2005. Together, this information is powerful weight of evidence toward

t he low likelihood of adverse effects on ecological integrity. This table also illustrates the importance of geospatial analysis to characterize probability (e.g. exposure frequency, spatial extent, co

- occurrence with sensitive species and habitats) of risk to non

- target organisms. It is inadequate to address potential risk and mitigation decisions using screening

- level information (representing obscure and environmentally

- irrelevant situations, in practice).

The Agency will consider improv ing the variety a nd represent at ive ness of the modeled scenarios in future risk assessments. New, more spatial ly explicit methods have not yet been fully developed and approved for use in regulatory assessments. In addition, EPA is currently working with its federal counte rparts to develop and implement an interim approach for assessing potential risk to listed species and their designated critical habitats. The Agency will not complete its endangered species assessment for sulfentrazone until the scientific methodology fo r risk assessment of listed species (and designated critical habitat) is finalized.

The registrant’s points about the actual percent crop area treatments are important but difficult to implement in a screening risk assessment. It is beyond the scope of t he current assessment to incorporate percent crop treated factors. We not e that a more refined10 assessment incorporating such factors must be able to reliably forecast the upper bounds of future percent crop treated factors.

FMC Comment 16: The statement regarding photo

- toxicity appears to infer the predominance of clear

- water conditions. While the impact of clear

- water conditions was assessed in the preliminary assessment, they are not reflected in the calculation of RQs for aquatic plants. Instead, a ph otolysis value of 98 days (from the soil photolysis study) was used in the aquatic exposure modeling to represent turbid conditions, which were then used to calculate RQs. Turbid water conditions are not consistent with the assumption of enhanced UV/photo

- toxic effects (conceptually more representative of clear

- water conditions). The guidance that is available from The Agency states that the direct photolysis value that is input into the EXAMS aquatic systems model is “... the minimum dark

- control corrected e nvironmental aqueous photo

transformation rate constant (corresponding to the maximum half

- life value).” ( http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm#Przm ). To determine potential for indirect effects due to effects on primary productivity and habitat, a quantitative characterization should be established and described instead of an assumed association. Indirect effects can be better addressed once adequate potential risk from direct effects is characterized. Given the significa nt corrections and screening

- level nature of risk presented in the preliminary risk assessment, FMC suggests that statements of indirect effects be evaluated against considerable revisions and refinement that are needed to correctly characterize potential direct risk. A food web model may be a useful to begin quantifying relationships between direct and indirect effects and FMC supports the introduction, development and implementation of such tool.

Turbid waters would be more characteristic of water bodies associated with agricultural

areas. Since sulfentrazone did not appear to degrade at rates approaching the aqueous photolysis study rate in some guideline ecologica l studies

, it was appropriate to put an
upper bound on exposure by using the longer soil ph otolysis rate

. The intent of this methodology is to bracket the risk profiles under different degradation rates which are derived from laboratory studies . In both cases the RQ is near the LOC ; this is indicative of potential risk.

EPA currently does not use a food web model to quantify the relationships between direct and indirect effects. However, EPA is currently working with its federal counterparts and other stakeholders to implement an interim approach for assessing potential risk to listed speci es and their designated critical habitats. Once the scientific methods necessary to complete risk assessments for listed species and their designated critical habitats are finalized, the Agency will complete its endangered species assessment for sulfentra zone.

FMC Comment 18: Because of major differences between ecological and human health drinking water assessments, this preliminary ecological assessment should not be used to support drinking water exposure in the future. While some information in the Tier II water modeling would be applicable (e.g. application rate, physical

- chemical properties), major differences11 between ecological and human health water exposure estimation exists, including but not limited

to:

• Receiving water body for ecological assessment (farm pond) versus index reservoir for human health • Environmental fate input guidance is different between ecological and human health

assessments • Application inputs for drift, application efficiency are different between ecological and h uman health assessments • Percent crop area is taken into account for human health drinking water assessments, whereas not for screening

- level ecological assessments

Drinking water exposure was estimated separately for surface waters using the Index Reservoir and for ground water s using the standard scenarios for PRZM

- GW along with characterization provided by the four prospective groundwater monitoring studies for sulfentrazone. EPA acknowledges that the environmental fate inputs can be different for various models depending on the requirements of each. The appropriate EPA guidance documents were followed for each model. For the surface water modeling of drinking water exposure , the default PCA for chemicals with both turf and multiple agricultural

us es on major crops sites was used as noted in the drinking water assessment. The preliminary ecological assessment was not used to support drinking water exposure.

FMC Comment 19: Potential exposure through spray drift and runoff to non

- target organism should take into account actual agronomic practices (application timing, rates according to soil characteristics, label restrictions including spray drift advisory language). Potential exposure to

non

- target plants and animals is not consistent with the lo w number of reported ecological incidents through EIIS over the past 12 years with wide

- scale use of sulfentrazone and should be reevaluated.

The preliminary assessment uses the best available information and to the extent possible provide s exposure estim ates from established models and scenarios. Low reported ecological incidents in the EIIS database do not necessarily mean that incidents do not occur and so the assessment may not always clo sely reflect incidents that may or may not be reported.

Conceptually, while direct foliar exposure has the potential to occur to non

- target plants adjacent to use areas, direct exposure to non

- target plants from uptake of sulfentrazone from the roots in residue studies is not expected to be detected in the plan t foliage that would lead to secondary exposure to terrestrial animals. In this case, the potential for terrestrial organisms via exposure from non

- target plant feed items would only be expected to be exposed to non

- target plants exposed to spray drift, no t spray drift and uptake through the roots from sulfentrazone originating as off

- field runoff. The conceptual model should be updated to consider this distinction, as it is important in the characterization of exposure and subsequent potential risk.12 The A gency agrees that there is likely to be less sulfentrazone exposure potential for non

target plants outside the treated area. Nonetheless, sulfentrazone could still be translocated from the soil to the roots and into the foliage as demonstrated in publishe d literature (see, e.g., Thomas et al., 2005 1 )

FMC Comment 20: This risk hypothesis is based on a screening

- level effort and deterministic approaches to identify potential risk to the most sensitive plants under hypothetical conditions that are protective, but not representative. The final conclusion of risk should in clude thorough analysis of the following critical aspects that are not currently considered in the EPA draft risk

assessment:

1) Labeled instructions for use, such as application rate and timing, are not represented in the preliminary draft assessment re sults for potential risk to terrestrial or aquatic non

- target plant systems. The federal label specifically limits or restricts the application rate of sulfentrazone based on soil texture and soil organic matter, which are spatially

- dependent parameters an d not currently addressed. 2) Terrestrial and aquatic non

- target plant effect endpoints used to calculate risk quotients do not represent community

- level adverse effect. 3) Spray drift exposure modeling (AgDRIFT) does not incorporate best

- available data to evaluate the impact of potential mitigation of spray drift exposure to non

- target plants adjacent

to use areas. 4) Spray drift mitigation does not address potential risk from runoff, which drives risk to the semi

- aquatic terrestrial habitat. Geospatial co

- occurrence of semi

- aquatic habitat and use areas should be evaluated in parallel with temporal patterns of exposure to terrestrial organism. 5) Edge

- of

- field runoff and possibly runoff connected with a vegetative buffer should be considered to revise the terrestrial exposure to dry and semi

- aquatic habitats (and relevant plants in those areas). 6) Sulfentrazone should be evaluated using all available field data (including more recent terrestrial field dissipation and aquatic dissipation data) to deter mine sensitive geographies and conditions. 7) Probabilistic risk assessment approaches that characterize the potential frequency, duration, spatial extent, and magnitude of potential adverse effects should be incorporated to fully represent federal label directions, chemical

- specific exposure, and spatial and temporal co

occurrence of use sites with sensitive plant ecosystems that could be impacted.

Decisions to mitigate risk after a screening

- level assessment of potential/theoretical risk would not effe ctively identify appropriate and meaningful mitigation to sensitive plant communities. Discussion of mitigation should only occur after a complete risk characterization is conducted so that appropriate measures are taken to proactively address concern arou nd impact to sensitive ecosystems.

1 Thomas, W.E., , S.C. Troxlera, W.D. Smith, L.R. Fisher, and J.W. Wilcut. 2005. Uptake, translocation, and metabolism of sulfentrazone in peanut, prickly sida (Sida spinosa), and pitted morningglory (Ipomoea lacunosa). Weed Science 53(4):446

- 450.13 The EPA has established protocols and procedures to conduct a preliminary risk assessment. This assessment reflects the current models and practices used when conducting risk assessments and does not incorporate models or methods currently in development. Incorporation of the spatially explicit assessment procedures recommended by the registrant can be valuable when more highly refined risk assessments are required.

FMC Comment 21: Molecular formula: The molecular formula should be C11H10Cl2F2N4O3S Aqueous Photolysis Half

- life: Aqueous photolysis is one of the principal dissipation routes in the natural environment. The Agency has listed half

- life values of 0.5, 0.05 and 0.05 days for aqueous photolysis at pH 5, 7, and 9 and it is important to evaluate and incorporate these values into the calculation of RQs. In nature, pH 7 is more representative for surface water modeling, therefore FMC recommends using the corresponding aqueous p hotolysis half

- life value (0.05 days).

EFED could not find anywhere in the document where a different molecular formula was used for sulfentrazone. However, if FMC points out a specific place where this needs to be corrected, EFED will incorporate the up dated mole cular formula information in a

m emorandum updating the assessment. The recommendations regarding the incorporation of the aqueous photolysis half

- life will be taken into consideration for future risk assessments, but see also our response to FMC Comment 16.

Additional data: Three terrestrial field dissipation studies are available an d will be submitted by FMC to provide additional information on soil movement to surface and groundwater. Results from these three studies indicate actual field half

- life values and should be considered rather than those previously observed in modeling. In addition, two aquatic dissipation studies have been conducted and will be provided to the Agency to help refine risk in surface water environments for sulfentrazone. The values found in these studies indicate that sulfentrazone is not persistent in the aqu atic environment. The following aquatic and field dissipation studies will be submitted to the Agency: 1. Dow, Karen. 2005. Sulfentrazone: Terrestrial Field Dissipation. FMC Study ID P

- 3778. FMC Corporation. Princeton, NJ.

2. Boatwright, Megan. 2012. Terrestrial Field Dissipation of Sulfentrazone in California Soils. FMC Study ID PC

- 0750. Golden Pacific Laboratories, LLC. Fresno, CA.

3. Culligan, John. 2008. Sulfentrazone: Terrestrial Field Dissipation in Canada. FMC Stu dy ID P

- 3949. FMC Corporation. Princeton, NJ.

4. Bertrand, Nicole. 2010. Sulfentrazone Aquatic Field Dissipation in Canada. FMC Study ID PC

- 0505. FMC Corporation. Ewing, NJ.14 5. Chen, Audrey. 2014. Greenhouse Aquatic Dissipation of Sulfentrazone and 3

- carboxylic acid Sulfentrazone. FMC Study ID P

- 4028R. FMC Corporation. Princeton, NJ.

EFED has received these studies. If these studies are deemed to provide information to meet specific environmental fate guidelines or provide significant supplementa l data potentially useful in risk assessments, a full Data Evaluation Review will be conducted for each study. F ollowing completion of the DERs , EPA will consider the appropriate use of these study results in future exposure assessments for sulfentrazone.

FMC Comment 22: Mobility and persistence data are available that suggest sulfentrazone is relatively persistent and mobile under the most vulnerable environmental conditions. The spatial extent of these conditions are not characterized or reported in thi s assessment, therefore the terms ‘under most’ should be revised to reflect actual field

- level information related to mobility and persistence potential

– or a quantification of the spatial extent of high

- mobility conditions should be conducted. A generali zed statement of expected movement does not take into account the impact of meteorological conditions and application timing that varies geographically and/or by crop type. Rainfall and evapotranspiration are two fundamental spatially

- and temporally

- depen dent hydrologic processes that must be considered when evaluating potential movement. The Agency conducted numerical simulations that incorporated standardized crop scenarios, not all of which are representative of labeled use patterns that intend to be pr otective of certain geographies and use patterns. The output from these numerical simulations does not provide adequate characterization of movement to conclude ‘expected movement’ because that output is based on highly

- conservative assumptions that may or may not be realistic or representative of environmental conditions associated with sulfentrazone use. Expected movement, in terms of standard EPA scenarios, is defined by the PRZM/EXAMS model, which implements many conservative assumptions.

In general, E PA agrees that these issues are valid and important when more refined risk assessments are mandated. EPA continues to work to make improvements in assessment methods that will provide more spatially explicit assessments and reduce conservativeness when it is defensible to do so. Incorporation of these procedures is, however, beyond the scope of the current risk assessment using currently accepted exposure assessment methods within EFED.

FMC Comment 23: FMC respectfully disagrees with EPA’s assessment that use of sulfentrazone is likely to result in contamination of groundwater and surface water. The studies referenced in the statement include groundwater leaching monitoring data from the upper 75th, 85th , and 95th percentile most vulnerable combinations of soil and weather conditions in the United States. The broad statement that those sites represent anything other than those most vulnerable conditions does not appear to consider that those soils actuall y represent a very small area of the US. Therefore, more clarity around the term ‘many soils’ appears warranted for revision in the final assessment. Use of the words ‘significant’ and ‘contamination’ are vague and should be revised to reflect the results of the screening

- level risk assessment that suggest that potential for risk to freshwater systems is relatively low, even if further refinement may be prompted for listed15 species. There appears to be no clear metric for risk to aquatic systems from groundw ater, so while sulfentrazone concentrations may be detectable in the most vulnerable groundwater conditions, the connection to surficial water systems is not evident. Trace level detection of sulfentrazone and SCA does not equal contamination. Therefore, t he use of the term ‘contamination’ in the context of an ecological risk assessment seems misplaced. Furthermore, neither sulfentrazone nor SCA metabolite has been reported in any ground water monitoring programs, as confirmed in EPA’s preliminary ecologica l risk assessment. In addition, sulfentrazone has low dietary risk based upon consumption of food and drinking water as outlined in the preliminary human health risk assessment (2014). Therefore, ‘contamination’ does not appear to apply to the human health risk assessment either and FMC suggests revising this language to eliminate vagueness. The preliminary risk assessment has not properly characterized groundwater exposure vulnerability. Modeling with appropriate Tier I or customized Tier II PRZM

- GW scenar ios (use of appropriate application rates based on texture and organic matter) would provide refinement in order to make assumptions concerning the potential for groundwater exposure. FMC is submitting three terrestrial field dissipation studies to provide additional information on sulfentrazone movement through the soil.

T he 4 PGW study results show a potential for leaching in roughly 25% or more of row crop production areas of the M idwest and Atlantic coastal plain. EPA did not use the term contaminatio n to imply whether or not the levels observed in groundwater should be associated with a measurable risk to organisms. The modeling approaches with PRZM

- GW are consistent with current EPA guidelines. If the registrant disagrees with the way these have been implemented they should provide a rationale for a change and present it to the Agency and request consideration of modifications of this policy.

FMC Comment 24: Within the context of the results from the groundwater vulnerability studies, groundwater monitoring data represent the upper 75th, 85th, and 95th percentile of the most vulnerable combinations of soil and weather conditions in the United States. In additi on, the highest, single maximum detection/concentration was found in the >95th percentile site and corresponded to an application rate that is higher than that on the federal label. In that study it was more important to define the break

- through, rather th an the absolute, environmentally

relevant groundwater concentration. Furthermore, there is no apparent relevance of single, maximum groundwater monitoring data in how ecological risk is characterized. FMC recommends removing groundwater from the ecological assessment unless there is a clear connection (quantifiable) to aquatic or terrestrial risk. The broad statement that those sites represent a ‘wide variety’ of sites in the US does not to consider that those most vulnerable soils actually represent a ver y small area of the US of highly

- specific, vulnerable soil and weather combinations. Crop growing areas where sulfentrazone is used must also be considered in parallel, as most vulnerable conditions in the US should be limited to where sulfentrazone is

act ually registered for use, further narrowing the variety of soils that are representative of conditions in the groundwater vulnerability studies. Revision of the term ‘wide variety of sites’ is suggested for publication in the final ecological risk assessme nt. A conclusive statement should consider the results from available groundwater data with respect to vulnerability of soil and weather. Furthermore, neither sulfentrazone nor SCA has been reported in any ground water monitoring programs, as confirmed in EPA’s risk assessment.16 The groundwater data are cited only for characterization purposes and have not directly been used to evaluate ecological risk. This information is cited in order to acknowledge the potential of herbicidal compounds found in groundwa ter affecting sensitive plants when, for example, impacted groundwater is used for irrigation purposes. EFED will consider revising the language of the risk assessment but we refer to our response to FMC Comment 23 and respectively ask the registra nt to p rovide specific data to support this request.

FMC Comment 25: Three corrections should be included in Table 11 of the refined assessment. The maximum shallow groundwater concentrations for parent sulfentrazone and SCA reported in the IN3 (75th site) should be corrected to: 0.09 ppb (1,149 d) and 0.07 ppb (753 d), respectively. The values reported by The Agency correspond to 9

- ft pore water samples (soil water, not groundwater). The third value that should be corrected is the maximum SCA concentration at the 85th percentile site, which should be <0.1 ppb (0.1 ppb is the LOQ).

EFED will inc orporate this information in a m emorandum updating the assessment.

FMC Comment 26: FMC agrees the EECs are believed to be conservative overall for the ecological ris k assessment. Table 12 should be updated to remove the 40

- day post

- emergence application pattern for all crops limited to pre

- emergent uses. Sulfentrazone is typically applied as a soil application prior to crop planting or emergence, with typical applica tion dates in agricultural settings from 40 days before planting until 3 days after emergence. EPA’s assumption that applications occur 40 days after emergence is incorrect for most agricultural uses. Foliar agricultural applications are only registered fo r use on sugarcane as a layby treatment, and dormant applications for strawberry, mint and rhubarb. Furthermore, application by air and the analysis presented in Table 12 should be updated to reflect that not all crops should be modeled using aerial applic ation. Aerial application represents a very small use area (<1%) and should be assessed as minor contribution with respect to non

- target effects in the risk assessment, compared to ground application that is the predominant application method. FMC

recommen ds the Agency reconsider their use of a surrogate value for aqueous photolysis in turbid water systems in their revised assessment in Table 13. While there may be a conceptual difference in degradation potential between turbid and clear water systems, ther e is no quantitative metric to justify the use of a surrogate value for aqueous photolysis. Aqueous photolysis is one of the principal dissipation routes in the natural environment. The Agency has listed half

- life values of 0.5, 0.05 and 0.05 days for aque ous photolysis at pH 5, 7, and 9 and it is important to evaluate and incorporate these values into the calculation of RQs. To be conservative, The Agency has assumed that all surface waters are at pH = 5, which lends the longest half

- life value to the expo sure modeling (0.5 days); however, in the calculation of RQs has used a surrogate half

- life value of 98 days which was estimated from the soil photolysis guideline study. Selection of a surrogate value for an environmental fate parameter when a measured, a cceptable value is available does not represent the environmental behavior and FMC suggests revising the aqueous photolysis input value. The justification The Agency uses to substitute surrogate data for measured data does not appear to be based on scienti fic data or experimental evidence (no references from the open literature were provided to support this substitution). In addition, if turbid water systems are assumed, as depicted by the preliminary assessment, the uncertainty factor associated with enha nced photo

- toxicity should be17 reconsidered. If a distinction is made that two types of systems that are at risk (turbid and clear water), more context is needed to understand and characterize the implications and corresponding potential risk of each type o f system in terms of: exposure spatial extent, frequency, duration, and relevant species effect endpoints. In addition to the selection of inputs to the aquatic exposure modeling, it is important to consider all of the conservative elements of the exposur e estimation technique to add context to the values reported in the preliminary ecological assessment. Some important, conservative assumptions in the PRZM/EXAMS aquatic exposure estimation procedure include: • EPA’s determination of 1 in 10

- year annual maximum concentrations as 90th percentile concentrations is inaccurate. Before estimating a “90th percentile”, the PRZM/EXAMS model first determines the highest daily pesticide concentration (or longer

- term conc entrations for non

acute exposures) for each year in a 30

- year simulation. The model then calculates the 90th percentile from these 30 values. For a 30 year period, EPA’s “90th percentile” is actually a concentration that would only be exceeded on three da ys in 30

- years (or a 1

- in

- 10 year event). On a daily basis, this estimate would actually be a 99.97th percentile. In other words, the concentration estimated by EPA would be less for 99.97 percent of days in the pond, assuming that the other components of the modeling were accurate and unbiased (which they are not). • To derive valid probabilistic exposure estimates (e.g., a 90th percentile), all key input variables must be modeled as distributions that reflect the range of plausible values for each variab le (particularly soils and topography). The only probabilistic variable in standard scenario PRZM/EXAMS modeling is the meteorology (most importantly, rainfall), and even the meteorology reflects only temporal variability, not spatial variability for a giv en crop. Conservative and sometimes implausible assumptions are made for almost all other key variables (e.g., 90th percentile estimates for rates of dissipation in the environment, high slope, zero interception by vegetative barriers). The compounding eff ect of these multiple, conservative assumptions is an implausibly high exposure estimate. • There is limited consideration of hydrology. The farm pond is assumed to be static, meaning that there are no inflows or outflows of water that would remove or dil ute pesticide concentrations. In streams and rivers, any pesticide runoff would disperse downstream and be diluted. In flowing water bodies, pesticides would only be expected to occur during short pulses rather than over extended durations. In addition, th e runoff water or sediment assumed to be carrying the pesticide to the water body has an associated volume that is not considered as an addition to the standard pond. In some scenarios used by EPA, the amount of soil assumed to enter the farm pond would be enough to fill it in well before the end of the 30

- year simulation period. Ignoring the addition of sediment to the pond and the dynamics of suspended sediment within the water body leaves an important pesticide transport and dissipation process

unaccount ed for. • The wind is assumed to always be blowing in the direction from the application site to the pond, an unrealistic assumption given that wind direction is variable. From the standpoint of the probability of exposure due to spray drift, this assumption is ov erly conservative. • The Tier II results represent a situation with a farm pond immediately adjacent to an agricultural field without any distance or buffer between the field and the water body. In many geographic regions, this hypothetical scenario is un likely to occur, with water bodies more often separated from the edge of a field by some distance. • The current PRZM3.12.2 crop standard scenarios do not include plant uptake as a potential source of pesticide removal from the treated field (EPA, 2009).18 • For foliar applications, the current EPA PRZM3.12.2 crop standard scenarios set foliar wash

off from plant leaves to 50%, which for many products is quite high (EPA, 2009). • The current EPA PRZM3.12.2 crop scenarios ignore the fact that farmers are un likely to apply pesticide during rainy conditions. • EPA uses an expert judgment procedure for identifying the soil series and geographical conditions that are supposed to represent 90th percentile worst

- case scenarios in the Tier II exposure concentratio n estimation process. It is not possible to determine whether these scenarios actually represent a 90th percentile vulnerability. This expert judgment procedure is used in lieu of a quantitative process that would examine the entire set of available soil a nd geographical data and then rank vulnerability based upon predicted exposure. • The EPA standard scenario simulations ignore the likelihood that farmers are unlikely to apply pesticide during rainy conditions. Rainy conditions increase the quantity of o ff

- field pesticide residues in run

- off because the other loss functions (e.g., degradation in soil) have not yet had a chance to take place before the pesticide runs off. • The EPA standard scenarios have not been calibrated with hydrology

- predicted resul ts and have not been compared to actual “real

- world” runoff and eroded sediment results. Rather, soil selection and input parameters are based upon recommendations from local crop experts. Thus, there is no way to assess whether off

- field runoff and eroded sediment is over

- estimated or under

- estimated. Because off

- field runoff and eroded sediment are primary mechanisms for off

field movement of pesticides (in addition to off

- field drift), inaccurate estimates of runoff and off

field erosion will result in i naccurate estimates of off

- field pesticide mass. • The assumption of a percent cropped area (PCA) of 100% in the standard farm pond scenario is overly conservative. A PCA of 100% is very rare, as has been shown in studies that have examined PCAs for small ponds in detail (Winchell et al., 2014). • The PRZM/EXAMS standard scenario modeling approach assumes that 100% of the standard pond watershed is treated with pesticide on the same date. In actuality, the area draining to or contributing spray drift to a receiving water body may be influenced by multiple fields treated on different days. Situations where applications occur over multiple days will result in lower exposure values in a receiving water body, making the standard EPA assumptions conservative.

EFED conducted both application timing runs to see what effect the timing of the year had on exposure assessment. The change in application dates only modestly changes the predicted exposure level (for example, the highest peak EECs were 17.9 and 14.4 pp b for applications nominally stated to be 40 days after and 1 day before emergence, respectively. In fact though, in years in which planting was significantly the 40 day POE applications could actually be right around the time of emergence. The registrant ’s request to eliminate the values for 40 days post planting for certain crops with only preemergence applications would generally be sensible. However, the standard scenarios used by EFED do not currently adjust the crop planting and maturity dates on an annual basis according to the changing weather patterns each year , including the fact that when soil moisture levels are high applications are less likely to occur (although in some cases, as the registrant notes, aerial applications will be made during s uch periods)

. Therefore EFED believes that the requested modifications and refinements should only occur when appropriate methods are approved to seamlessly vary agronomic practices and sulfentrazone applications according to environmental conditions (weat her variations) on annual basis at each site that is modeled.19 FMC Comment 27: Sulfentrazone is predominantly used as a soil

- applied herbicide prior to crop emergence or planting. In pre

- emergent residue studies, parent sulfentrazone has not been measured at detectable levels in plant s and is not well represented by the assumptions used in the EPA T

- REX model. A revision of expected plant residues should be conducted as most registered crops are not directly sprayed and residues on avian feed items due to spray drive should be considerably less than those derived from standard methods in the T

- REX model.

Post

- emergent residue data may better represent expected residue in food items in the environment

– especially chronic residues, as some PHIs may be rela tively long to estimate maximum expected residue. Post

- emergent applications are limited to only a few crops and parent residue values resulting from foliar application to mint (MRID 45393503), strawberry (MRID 47311408), rhubarb (MRID 48514802), and sugar cane (MRID 45077904, 45077905) are not detectable to the limit of detection or the limit of quantitation. This foliar residue data is on file with the Agency and could also provide a more reasonable residue values for the T

- REX model. The crop residue data suggests lower potential maximum and chronic residue, compared to default T

- REX assumptions.

The screening

- level approach of using maximum potential residue (acute) to describe chronic exposure does not consider best

- available data and is overly

- conserv ative for describing risk. Using acute exposure with a chronic effect endpoint is further compounded by inherent, conservative, simplistic assumptions by the consumption and exposure duration defined in the T

REX model. The T

- REX model calculates dietary e xposure for any given bird species that consumes 100% of its diet from each food category (short grass, long grass, etc.) and that diet always contains the maximum chemical residue. The model further calculates dietary exposure based on a consumption rate that is not likely (e.g. a 20

- g bird consumes 114% of its body weight daily). Finally, the model assumes that the maximum residue in feed items is present over an infinite period of time, essentially mismatching an acute exposure with a chronic effect.

F

MC understands that the standardization of avian risk is a useful tool to indicate potential risk, but further revision to the draft assessment should be done to address the chemical

- specific expected exposure estimate and conservative consumption assumpti ons that apply to sulfentrazone. Birds have a varied diet that varies temporally and spatially and should be considered with the co

- occurrence of chemical application areas (access to feed items that contain potential residues). For example, probabilistic techniques are available that can be easily employed to address crop

- and chemical

- specific risk evaluation (eg ECOFRAM, 1999, Moore et al., 2009; Brain et al., 2014, Moore et al., 2014).

It is difficult to preclude risk from vegetation or other food item residues on the field at the time of application. Sulfentrazone is used as a no

- till herbicide in the spring and fall prior to plant or emergence. Residual weeds on the field will be exposed to sulfentrazone applications. While birds and mam mals may no t be exposed to sulf entrazone on the crop, they may be exposed through foraging on food items in the field such as weeds and insects. In the absence of conclusive proof that there are not sulfentrazone residues20 associated with dietary items left on the field

, EPA will not revise EECs generated from the standard TREX model.

FMC Comment 28: There are two avian reproduction studies available for sulfentrazone and they are with bobwhite quail (MRID 43355901) and mallard duck (MRID 443355902). Taking both avian reproduction studies into consideration, a NOAEC of 100 ppm should be considered for risk assessment and both of the studies should be considered as core studies.

In both studies the treatment groups were 0, 1, 10 and 100 ppm. Based on the initial evaluation of the study director for bobwhite quail, the LOAEC could not be determined, but the NOAEC was determined to be 100 ppm. However, per agency’s evaluation the LOAEC was concluded to be 100 ppm and, the NOAEC 10 ppm. This was based on reductions i n 14

- day old survivor weight with an 8% reduction at the LOAEC relative to the control. However, we believe a reduction in weight less than 10% in absence of any other significant physiological effects should not be considered as an adverse effect. Therefo re, a NOAEC of 100 ppm should be used for risk assessment.

In order t o respond to the comments adequately we went back and more carefully considered the study. The previous assessment classified the study as supplemental because the test concentrations were too low to support the proposed uses on turf and lawn at that time (1995). Based on this criteria

, we deemed the study acceptable for the
current application rates and use patterns that fell within the range of the study. We feel that there is not en ough evidence to discount the reduction of in body weight of 8% and consider this a significant effect . Based on the previous assessment using this endpoint is sufficient for the risk assessment and we cannot move away from it without further evidence

. O ur analysis revealed

, however

, that the high control mortality during the study reduced the statistical power of the study. Despite this lack of statistical power, the study was still able to detect the 8% decrease in female body weight. Statistical anal ysis was not able to detect differences in eggshell difference between the control and the highest treatment group even though there was a statistical difference between the lowest treatment group and highest treatment group. There also appears to be a red uction in the number of eggs between control group and the highest treatment group (100 ppm) al though this difference was not statistically detected, likely due to the high control mortality. Current EFED guidance states that control mortality more than 1 0% in an avian reproduction study is reason to reject the study. The control mortality in this study was 12.5%. If the registrant finds that the current endpoint is unacceptable, the Agency could invalidate the study and require a new bobwhite reproducti on study to confirm or refute the endpoints that are used.

For mallard duck (MRID 443355902)

, the NOAEC and LOAEC were determined to be 100 ppm and > 100 ppm, respectively. In this study none of the measurement endpoints were adversely affected. However, the Agency classified this study as supplemental because no LOAEC was established. Potentially, the NOAEC could be higher than 100 ppm. However, conser vatively 100 ppm could be used in risk assessment as NOAEC and not the LOAEC. Therefore, the Agency should reclassify this study as a core not a supplemental study.21 EFED guidance states that studies with non

- definitive endpoints be classified as supple ment al but may be used in risk assessments.

In its recent review and guidance document entitled: “Assessing Risks to Endangered and Threatened Species from Pesticides”, the National Academy of Sciences (NRC, 2013) outlines the use of best available data and quality of data to be used in environmental risk assessments. FMC is in agreement with the recommendation.

In addition, several methods have recently been proposed to evaluate the relevance and quality of ecotoxicity studies. EPA should consider thes e methods when evaluating the relevance and quality of studies for risk assessment (Breton et al., 2009; Breton, 2014; Hall et al., 2010, 2012; Van Der Kraak et al., 2013; Solomon 2014).

Breton, R. 2014. Data relevance and Data Quality for Ecological Ris k Assessment. Presented at ACS/IUPAC San Francisco, August 2014. Intrinsik Environmental Sciences Inc. Breton, R. G. Gilron, R. Thompson, S. Rodney, and S. Teed. 2009. A New Quality Assurance System for Evaluation of Ecotoxicity Studies Submitted Under th e New Substances Notification Regulations in Canada. Integrated Environmental Assessment and Management 5(1):127

- 137

EFED appreciates the input and additional methods that might be used.

FMC Comment 29: Exposure to marine/estuarine systems is expected to be diluted well beyond the standard EPA ‘pond’ that is simulated and reported in Table 23. The standard EPA pond is 1 ha in surface area and 2 meters deep and does not represent marine/estuarine systems, but is considered protective of them. While no existing correlation in dilution and volume differences between the standard EPA pond and an actual marine/estuarine system has yet been available, without a policy around this dilution from The Agency, only a qualitative assessment can be assumed. RQs are deterministic and quantitative in nature and do not lend themselves to the concept of uncertainty in dilution or any other environmental metric. Therefore, FMC suggests that the RQ generated for marine/estuar ine species, which is not derived from measured data, be revised to be reported in a more qualitative format that reflects exposure uncertainty due to the considerable dilution potential difference between the standard EPA pond and marine/estuarine systems . The EPA standard peppers scenario is not representative of all existing and proposed use of sulfentrazone. Tables 23 and 24 contain several errors when estimating risk such as: 1. Sulfentrazone is not registered at the state level in Florida for agricul tural uses. 2. Assessment with aerial application is not representative and accounts for less than 1% of all applications in the United States on all registered crops. 3. Environmental fate inputs are screening

- level, according to guidance except aqueous photolysis.

An updated Table 23 would report the standard EPA PA, NC, and OR apple scenarios, ground application, and appropriate aqueous photolysis rate (0.05 days pH=7; all other environmental fate matching EPA’s screening

- level input selections). FMC generated chronic exposure values using the EPA Surface Water Calculator (SWCC v 1.103 and corresponding .SCN scenario files), assuming the EPA Standard Pond and maximum application rate (0.375 lb/ac). Resulting22 chronic exposure values (21

- day) for the st andard EPA PA, NC, and OR apple scenarios were 0.709, 0.68, and 0.621 ppb, respectively. Using the NOAEC of 0.003 ppm (3 ppb), updated RQ values for standard EPA PA, NC, and OR Apple scenarios can be calculated as: 0.24, 0.22, 0.21, respectively. Even thou gh dilution would be very different for marine/estuarine systems (more dilute, lower exposure estimate), these RQs are below the Agency’s level of concern.

EFED will provide explicit representation of the lack of sulfentrazone registration in the entire s tate of Florida in a m emorandum updating the assessment. We can note that the registrant believes that aerial applications represent less than 1% of all uses. EFED notes that, because, by all other transformation pathways conversion is much slower, the

ove rall modeling results can be highly sensitive to the use of the 0.5 day aqueous photolysis have life. The available ecological studies (e.g., fish toxicity studies in waters subjected to sunlight or simulated sunlight) fail to confirm that photolysis is as relevant a transformation pathway in natural waters as the use of this half

- life implies.

FMC Comment 30: Tables 30 and 31 report the output from the TerrPlant model and corresponding screening

- level risk results for non

- target plants but does not represent a characterization of the risk. The TerrPlant model contains the following assumptions and limitations t hat could be refined beyond the screening

- level (Trask et al., 2010a,b): • The semi

- aquatic non

- target area is assumed to be one

- tenth the size of the target application area. This assumption is based on observations of aquatic areas in Georgia. However, the size ratio is likely to be highly variable across agricultural areas in North America. • The spray drift component of TerrPlant only considers the application method and does not include additional factors such as wind speed, droplet size and height o f pesticide release that may affect the quantity of pesticide moving off the field as spray drift. • TerrPlant assumes the maximum application rate which may not be representative (or allowable in specific environmental conditions according to the federal label) • The model conservatively assumes that runoff occurs at the time of application, an unlikely event given that farmers generally avoid applying pesticides on rainy days. • Both runoff and spray drift are assumed to be distributed uniformly throug hout the non

- target area. In reality, there is typically a decrease in the quantities of runoff and spray drift reaching areas of increasing distance from the application area. • TerrPlant assumes that runoff and spray drift reach the non

- target area at t he same time, and that non

- target plants exposed to the pesticide residues are in the sensitive, early emergent life stages. Both of these assumptions are conservative. • Estimated Exposure Rates are calculated using only the solubility of a pesticide. Th e calculation of EERs does not consider other environmental fate parameters, such as the water and soil half

- lives and Kd of the pesticide, which affect the amount of the pesticide that binds to soil and sediment and pesticide movement within these matrice s. These parameters may considerably affect pesticide concentrations in runoff and spray drift in the non

- treated area to which the terrestrial plants are exposed. • Calculation of the RQ for non

- target plants exposed to runoff only considers seedling

eme rgence and does not consider other life stages, which may be more or less sensitive. • TerrPlant uses effect metrics from tier II terrestrial plant studies to assess risk. It assumes that the effects observed in these studies of single species in pots wou ld be equivalent for other23 species in the wild. Currently, there are no field data to evaluate the exposure estimates generated by TerrPlant. Thus, there is uncertainty concerning model performance in the real world. The binary trigger of RQ>LOC is a usef ul mechanism to determine whether or not a refined risk assessment should be conducted and for which exposure scenarios. For those exposure scenarios, refined techniques should be used to characterize the magnitude, direction, and uncertainty associated wi th potential for risk. Refined, community

- level effects measures, which are more suitable for use in discerning risk to non

- target plants off

- field, should be developed and compared to the results of a refined exposure assessment. FMC recommends the use of refined methods for exposure and community

- level effects. For a recent review of refined methods, see Brain et al. (2014)

This is a screening level assessment conducted with approved models and methods. While the EPA evaluates alternative models such as AgDISP, they are not suitable for risk assessment purposes at this time. The EPA appreciates the points made in this

comme nt and will consider these points in future assessments.

FMC Comment 31: The combination of conservative drift/runoff assumptions along with a broad label interpretation and worst case endpoint selection lead to the apparent need for large buffers at the screening level. Exclusive use of the AgDRIFT model should be avoided because of the known limitations and availability of more current data

- sets (e.g. RegDISP http://www.stone

env.com/agchem/agres.php#agdownload and recent research on AgDISP

– primarily s upported by the USDA). Beyond spray drift alone, a principal reason that terrestrial and semi

- aquatic plant risk scenarios exceeded 1000

- ft is because the runoff contribution is the “Tier 0” value of 5%. The semi

- aquatic scenario assumes that runoff contri bution should be multiplied by a factor of 10, assuming that 10x the upland area contributes to runoff in a unit area of semi

- aquatic habitat. Therefore, runoff is 10x more important than drift alone for the semi

- aquatic scenario, yet no refinement of runo ff exposure has been conducted by The Agency. This is an over

simplification that could be revised using a model such as PRZM to estimate edge

- of

- field values for acute and chronic exposure to plants. For example, the 99.7th upper

- bound percentile
exposure of daily values within a 30

- year edge

- of

- field PRZM simulation, using the standard EPA soybean PRZM scenario, results in runoff fraction of 0.0024 (0.24% of the total 0.375 lb ai/A), compared to the 5% assumed by the EPA TerrPlant model. The screening

- le vel assessment, summarized in Tables 32

- 35, do not characterize the spatial and temporal co

occurrence of plant species and use pattern by crop or geography. The federal label describes in detail the application rates corresponding to different soil condit ions. While many uses on the label are up to 0.375 lb ai/A, the label carefully limits this rate by soil type and soil organic matter composition, protecting vulnerable areas. So, while some areas/crop geographies do allow the maximum application rate, the screening

- level assessment conducted by the Agency does not characterize the extent to which these conditions occur and the corresponding co

occurrence of adjacent semi

- aquatic and dry habitat. FMC suggests that this first effort by the Agency represents a screening

- level effort that indicates the need for further, careful consideration of drift and runoff refinements and actual label practices before mitigation of spray drift is addressed. The most sensitive plant species endpoint was selected for establi shing buffers (monocot and dicot). In cases where sensitive surrogate species endpoints indicate potential risk from off

- target movement, it is important to relate those endpoints to the biological24 equivalent in the environment and its corresponding ecosys tem function. One way to do this is by using a species sensitivity distribution to represent the ecosystem, instead of using the most sensitive single species. The protection goal of the assessment is at the plant community level, not the single species le vel. For example, if cucumber is the most sensitive dicot surrogate species then the biological equivalent of the cucumber in nature should be identified through expert opinion and open literature resources (e.g. USDA plant database http://plants.usda.gov/ java/). Then, context for the ecosystem function of the natural equivalent of the cucumber would be more clear and relevant to address potential mitigation As sulfentrazone is predominantly used as a pre

- emergent herbicide, efficacy depends on soil

covera ge rather than leaf contact. To maximize soil coverage, spray nozzles that provide medium/coarse droplet size are desirable. It is impractical and extremely unlikely for a grower to use a fine spray droplet size if the product is to be used in compliance w ith the label and current application practices. For ground applications, FMC recommends that spray drift data used in the assessment be derived from medium/coarse datasets under wind

- speed conditions specified on the federal label. The draft ecological a ssessment should be revised to include more appropriate exposure estimates of runoff contribution within dry and semi

- aquatic habitats. In parallel, best

- available spray drift data should be included to adequately address potential risk from the ‘spray dri ft’, ‘dry’, and ‘semi

- aquatic’ TerrPlant scenarios. The RegDISP model can be used to effectively identify data corresponding to the relevant application patterns needed for the risk assessment. FMC advocates for the inclusion of best

- available spray drift data to evaluate potential risk to non

- target plants.

The EPA periodically evaluates and tests new models (and the data used to inform such models) to be used in the risk assessment process to better refine the assessment. While the EPA appreciates the utility of alternative models and the additional data that may be available to support the models , the models and the methods for using them in this assessment represent the current m ethod s approved for risk assessment purposes.

As part of the addendum, EPA evaluated spray drift using larger droplet size s . However, since the size distribution of spray droplets delivered may be broad, the EPA used a r ange of droplet sizes to characterize risk. In general, the EPA must include the most conservative scenario in the ecological risk assessment and be inclusive of all sulfentrazone product labels

.

FMC Comment 32: The lack of ecological incident reports over the last 9 years suggests that spray drift and off

- site management associated with more current grower techniques and practices is an important consideration in the risk assessment. Furthermore, there are no
rep ortable FIFRA 6(a)2 documentation for sulfentrazone causing adverse effects on crops due to spray drift, runoff or carryover harming neighboring fields and/or property. This lack of incident reports suggests that sulfentrazone is not likely to cause advers e effects to non

- target plants. The conclusion of potential risk to non

- target plants is not consistent with the lack of incidents over a significant period of time corresponding to wide

- scale use and should be revised. FMC notes that Table D1 on page 134 contains errors or requires additional consideration by the Agency:25 1. Reported formulations (i.e granular, emulsifiable concentrate, water soluble packet) are not registered for agricultural use and indicate some degree of uncertainty in the reporting. 2. The relevance of the ecological incidents defined with the “Certainty” values of “Possible” and “Probable” should be carefully considered when assessing risk of sulfentrazone.

The lack of ecological incident reports does not necessarily indicate that incidents did not occur. The risk assessment considers both the risk incidents as well as the risk estimation and characterization when characterizing risk in an assessment. EPA will review Table D1 on page 134 of the preliminary risk assessment to dete rmine if there are any errors. If corrections are required they will be incorporated into the update memorandum.

FMC Comment 33: FMC agrees that the screening

- level dietary exposure using the T

- REX model for small birds or small mammals is conservative and overestimates potential risks. The risk assessment should be revised to correct for the assumptions/inputs from the T

- REX model: 1. Any given bird species consumes 100% of its diet from each food category (short grass, long grass, etc.) 2. Avian diet always contains the maximum chemical residue 3. Dietary exposure calculated on a consumption rate that is unlikely (e.g. a 20

- g bird consumes 114% of its body weight daily) 4. Maximum residue in feed items is present over an infinite period of time, not providing correlation from acute exposure to chronic effects.

TREX is the standard model for on

- field risk in preliminary risk assessments. While the EPA appreciates the comments, the TREX model is not being revised at this time. If and when new data are submitted and validated by the Agency, modeling procedures can be appropriately revised.