UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D

. C. , 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### MEMORANDUM

SUBJECT:

FROM:

THRU :

TO: Drinking Water Assessment for the Proposed New Use of Sedaxane as a Seed Treatment on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; except soybean), Rapeseed (subgroup 20A), and Potato PC Code: 129223; DP Barcodes : 405391 and 407956



### Rochelle F. H. 

### Bohaty Ph.D., Chemist /' // !)_ 

### James Hetrick Ph.D., Senior Science

# Adviso~**(A.~~~** 3/t e'



# /t 3 Environmental Risk Branch 3 Environmental Fate and Effects**Divi~ion** 

### (7507P)

Dana Spatz, Branch

# Ch~ Rosanna Louie-Juzwiak, Risk Assessment Proce s Environmental Risk Branch 

### 3 Environmental Fate and Effects Division (7507P)

Heather Garvie

, Risk Manager Reviewer Cynthia Giles-Parker, Chief Fungicide Branch Registration Division (7505P)

EXECUTIVE SUMMARY



### This memorandum provides a drinking water assessment (DW A) for the proposed registration of sedaxane as a seed treatment on corn, sorghum, dried shelled pea and bean (Subgroup 6C; except soybean), rapeseed (subgroup 20A), and potato to protect against certain soil

- borne and seedborne diseases.

Sedaxane was recently registered for use as a seed treatment for small grain cereals (barley, wheat, oats, rye and triticale), soybean and canola. The proposed new uses are on the label for Sedaxane 500FS/VibranceTM (Al6148C).

This DWA takes into account sedaxane (SYN524464), a mixture of two isomers separately numbered SYN508210 (trans-isomer of sedaxane) and SYN508211 (cis-isomer of sedaxane), and two known environmental transformation products of equal toxicological concern, CDCD668094 andCDCD668095. These two chemicals were only observed in aquatic photolysis studies; therefore, these residues were only considered as part of the surface water modeling. Sedaxane, as well as its transformation products of concern, are referred to collectively as total toxic sedaxane residues. This DWA includes estimated drinking water concentrations (EDWCs)



# '

### 2 based on Tier I surface water and Tier I groundwat er model simulations for all the proposed sedaxane uses.

Seed treatment use of sedaxane on potato is expe cted to result in the highest exposure scenario ( Table 1 ). Peak and post breakthrough PRZM-GW ED WCs in groundwater resulting from the proposed sedaxane uses are not expected to be > 22.4 μ g/L and 19.3 μ g/L, respectively. For the proposed potato use, an applic ation made every other year was investigated. The Wisconsin Central Sands scenario resulted in a peak PRZM-GW EDWC of 15.1 ppb and a post breakthrough average of 13 ppb. The next highest exposure was with the North Carolina Coastal scenario, which resulted in a peak PR ZM-GW EDWC of 8.09 ppb and a post breakthrough average of 6.95 ppb. These EDWCs are higher th an those estimated in the new chemical drinking water assessment. 1 

### These groundwater EDWCs are expect ed to be conservative based on the assumption that all the sedaxane appl ied to a seed is available for leaching.

Table 1. Results Summary: EDWCs fo r Total Toxic Sedaxane Residues For the Proposed New Use on Potato at 0.1 lbs ai/A.

Assessment Tier/

Model Crop Sedaxane Total Toxic Sedaxane Residues
Acute Peak EDWC

μ g/L (ppb) Chronic/Cancer Yearly Mean μ g/L (ppb) Acute Peak EDWC

μ g/L (ppb) Chronic/Cancer Yearly Mean μ g/L (ppb) Tier I/ FIRST* Potato 4.1 1.2

Tier I/ SCI-GROW Potato 0.1 0.1 Assumed sedaxane application every
year. Tier I/ PRZM-GW Potato 22.0 19.3**

Tier I/ PRZM-GW Potato 15.1 13** Assumed sedaxane application every other year.

The two highest EDWCs were for Wisconsin Central Sands and the NC Coastal Plain scenarios, respectively. 8.09 6.95**

* Surface water EDWCs have been corrected for a percent cropped area (PCA) of 0.91. ** Value is not a yearly mean but the mean concentra tion following breakthrough (time to breakthrough is 1870 days; other simulations resulted in breakthrough < 1 year after initial application).


### The PRZM-GW estimates are higher than those calculated using SCI-GROW and FIRST. Therefore, PRZM-GW EDWCs are the recommende d EDWCs for use in the human health risk assessment. Depending on the scenario simulated, the EDWCs range from 3.6 μ g/L to 22.0 μ g/L and 3.5 to 19.3 μ g/L for peak and post breakthrough con centrations, respectiv ely. Model outputs indicate that the time to break through (the time it takes for se daxane residues to reach the underground aquifer) ranges from 3811-10,389 da ys depending on the scenario. With the exception of the potato application made once per year, this analysis is based on 30 years of sedaxane use as a seed treatment with two plantings per year.

1 U.S. Environmental Protection Agency, Bohaty. R. Drinking Water Assessment for the Registration of Sedaxane, Dec. 21, 2011, PC Code: 129223; DP Barcode: 382528, 389464

### 3 Based on HED’s estimated level of concern, limiting sedaxane use in areas known to be vulnerable to groundwater contamination is reas onable given the range of EDWCs calculated using the various scenarios in PRZM-GW modeli ng. Specifically for potatoes, some of the less vulnerable of the standard scenarios results in peak and post breakthr ough concentrations of 3.6
μ g/L and 3.5 μ g/L, respectively. Additional evaluation (Tier II) of the percent organic carbon content in the top 20 cm of the soil for four different scenarios indicate that groundwater EDWCs will likely be below HED’s level of concern if the organic carbon content of the soil is above 2%. Another evaluation was conducted to assess the impact of sedaxane a pplications every other year. This analysis indicates that only the Wisconsin Central Plain scenario predicts average breakthrough sedaxane concen trations greater than 10 μ g/L.

Label Considerations:

On page one of the proposed Vibrance TM 

### label (EPA Reg. No. 100-1374) for potato, a list of use sites is presented; however, potato is not included. The sedaxane a pplication rate for potato is to treat 0.08 fluid oz product/100 lbs of seed (2.5 grams ai/100 kg seed). These application rates are required to control Rhizoctonia solani and Helminthosporium solani

. On page eight of the proposed Vibrance TM 

### label (EPA Reg. No. 100-1374) for corn, sorghum, dried shelled pea and bean (Subgroup 6C; except soybean), and rapeseed (subgroup 20A) the use rate mg a.i./seed has been changed from the currently registered label. This appears to have been done to make the use rates consistent; howev er, the update should be 0.0041-0.0076 mg a.i./seed to correspond with 0.08-0.16 oz product/100 lb seed.

### 4 PROBLEM FORMULATION

Sedaxane (CAS Name: N-[2-[1,1 ′ -bicyclopropyl]-2-ylphenyl]-3-(difluoromethyl)-1-methyl-1Hpyrazole-4-carboxamide CAS No.: 874967-67-6; co mpany code SYN524464; structure shown in Figure 1 ) is a mixture of two diastereoisomers, designated trans - and cis -isomers. These isomers are separately numbered; SYN508210 ( trans -isomer of sedaxane) and SYN508211 ( cis -isomer of sedaxane). The proposed specification for sedaxane technical product is 85% by weight SYN508210 ( trans -isomer) and 13% by weight SYN508211 ( cis -isomer). Sedaxane belongs to the chemical class of pyrazole -carboxamides in the succinate-dehydrogenase inhibitor (SDHI) class of fungicides, which inhi bits complex II respiration.

NH O

N N HF 2 C

CH 3 H H

NH O

N N HF 2 C

CH 3 H H

Trans- isomers SYN508210 NH O

N N HF 2 C

CH 3 H H

NH O

N N HF 2 C

CH 3 H

H

Cis -isomers SYN508211



### Figure 1. Chemical Structure of Sedaxane

This DWA uses modeling to estimate groundwater and surface wate r concentration of sedaxane and its environmental transformation products resu lting from the uses of sedaxane on sites that are vulnerable to pesticide contamination. This analysis provides estimated exposure concentrations that may occur in drinking water for the human health diet ary risk assessment.

ANALYSIS

Use Characterization

Sedaxane was recently registered in the United States as a seed treatment for small grain cereals (barley, wheat, oats, rye and triticale), soybean and canola to protect ag ainst certain soil-borne and seed-borne diseases. Target fungal pathogens for sedaxane include: Fusarium Spp. Pythium
spp., Septoria , smut ( Ustilago tritici ), stink bunt ( Tilletia caries ), loose smut ( Ustilago nuda ), head smut ( Sphacelotheca reiliana ) and Rhizoctonia spp. In addition to th e technical product, three end use products were registered. Two of the proposed end use products contain a

### 5 combination of multiple pesticide active ingredients, including difenoconazole, mefenoxam and thiamethoxam, as described in Table 2 . These uses are considered widespread.

Table 2. Sedaxane End Use Produc t Summary for the United States

Formulation Sedaxane 500FS A16148C Vibrance TM A16874F A17511B

lb a.i./gal product percent lb a.i./gal product percent lb a.i./gal product percent

Active Ingredients Sedaxane 4.3 45.45% 0.115 1.22% 0.067 0.72% Difenoconazole None 0.552 5.86% 0.308 3.34%

Mefenoxam None 0.138 1.46% 0.079 3.34% Thiamethoxam None None 0.256 2.78%

Currently Registered Uses Canola Cereals Cereals Cereals Soybean

Proposed New Uses corn

None None dried shelled pea and bean (subgroup 6C;

except soybean) potato rapeseed (subgroup 20A including canola)


### Sedaxane is applied as a water-based slurry to seeds which are then planted according to planting practices employed for the respective crops. The cu rrent sedaxane application rates for barley, canola, oats, rye, soybean, tri ticale and wheat are provided in Table 3 . The number of applications of sedaxane that ca n be applied per season is limited to two. This permits growers to reapply sedaxane treated seeds in the event of crop failure. This per season application rate restriction does not restrict the number of sedaxane applications that may occur within a calendar year. Based on the currently registered uses there are a number of potential crop rotations including barley-wheat, soybean-rye and soybean-wheat (list ma y not be exhaustive). Therefore, it is possible; however, unlikely that four appli cations of sedaxane could be made based on a crop rotation both resulting in crop failure once. Due to this concer n the registrant has agreed to update currently labels to limit sedaxa ne applications to two per year. 2 

### This permits initial planting of sedaxane treated seeds followed by eith er replanting of treated seeds in the event of crop failure or crop rotation.

The registrant has proposed the use of sedaxane as a seed treatment on corn, sorghum, dried shelled pea and bean (Subgroup 6C; except soyb ean), rapeseed (subgroup 20A), and potato. The proposed new uses are only included on the label for Sedaxane 500FS/Vibrance TM 

### (A16148C)—the single active i ngredient formulation.

The proposed application rates for corn, sor ghum, dried shelled pe a and bean (subgroup 6C; except soybean), rapeseed (subgroup 20A), and potato are provide in Table 4 

### . The per year application rate restriction is also two; except for potatoes where a yearly sedaxane application rate is restricted to one application.

2 Phone conference with Syngenta on January 16, 2013.Table 3. Currently RegisteredSedaxane Application RatesCrop Residential Agricultural ForestryMaximumApplicationRatelb a.i./100 lb ofseedMaximumSeedingRatealb seed /AMaximum SingleApplication Ratelb a.i./A(kg a.i./ha)Maximum TotalApplication RateMaximum Numberof Applications PHI (days)
c REI (hours)
c MRI (days)
cMinimumPlanting Depthdin Inches (cropprofile state andyear)/ CommentsPer Yearlb a.i./APer CCblb a.i./APer Yearlb a.i./APer CCblb a.i./Abarley√0.005 98 0.0053 (0.0045) 0.0106 0.0106 2e2 NS NS 01⁄2 (Colorado2002)canola√0.005 5 0.0003 (0.0003) 0.006 0.006 2e2 NS NS 01⁄4 (Kentucky2010)oats√0.005 87 0.0047 (0.0042) 0.0094 0.0094 2e2 NS NS 01⁄2 (Colorado2003)rye√0.005 109 0.0059 (0.0053) 0.0118 0.0118 2e2 NS NS 0Surface (Georgia2006)soybean√0.005 167 0.0084 (0.0075) 0.0168 0.0168 2e2 NS NS 03⁄4 (Arkansas2005; Louisiana2003; Michigan2002)triticale√0.005 109 0.0059 (0.0053) 0.0118 0.0118 2e2 NS NS 0 No Profilewheat√0.005 156 0.0084 (0.0075) 0.0168 0.0168 2e2 NS NS 0 >2 (North Dakota)a.The maximum seeding rate was developed based on data provided by BEAD—J. Becker; S. Ratnayake.Acres Planted per Day and Seeding Rates of Crops Grown inthe United States,March 24, 2011.b.Reported as per crop cycle or per seasonc.PHI – Preharvest interval; REI – reentry interval; MRI – Minimum retreatment intervald.The minimum planting depth was taken from the USDA’s National Information System for the Regional IPM Centers crop profiles. Brackets indicate which state’scrop profile the value was taken from.e.The number of applications of sedaxane that can be applied per season is limited to two. The registrant plans to update labelsto limit the number of sedaxaneapplications to two per year.NS= not specified7Table 4. Proposed Sedaxane Application RatesCrop Residential Agricultural ForestryMaximumApplicationRatelb a.i./100 lb ofseedMaximumSeedingRatealb seed /AMaximum SingleApplication Ratelb a.i./A(kg a.i./ha)Maximum TotalApplication RateMaximum Numberof Applications PHI (days)
c REI (hours)
c MRI (days)
cMinimumPlanting Depthdin Inches (cropprofile state andyear)/ CommentsPer Yearlb a.i./APer CCblb a.i./APer Yearlb a.i./APer CCblb a.i./Acorn√0.04 33e0.013 (0.015)0.026 0.026 2 2 NS NS 302 (Nebraska 2007;includes Kansas,North Dakota, andSouth Dakota)dried shelledpea and bean(subgroup6C; exceptsoybean)√0.005 42f0.002 (0.002) 0.004 0.004 2 2 NS NS 302 (Colorado2003); 1-3(Kansas 2004);1.5 (Minnesota2001);potato√0.003 2875g0.1 0.1 0.1 1 1 NS NS NA3-4 (Florida2008); 2-4(Montana 2002);2-3 (Texas, 2009)rapeseed(subgroup20Aincludingcanola)√0.005 5 0.0003 (0.0003) 0.006 0.006 2 2 NS NS 30h1⁄4 (Kentucky2010)sorghum√0.005 9 0.0046 (0.0052) 0.0092 0.0092 2 2 NS NS 302 (Kansas 2000);2 (Oklahoma2009)a.The maximum seeding rate was developed based on data provided by BEAD—J. Becker; S. Ratnayake.Acres Planted per Day and Seeding Rates of Crops Grown inthe United States,March 24, 2011.b.Reported as per crop cycle or per season on label(s).c.PHI – Preharvest interval; REI – reentry interval; MRI – Minimum retreatment intervald.The minimum planting depth was taken from the USDA’s National Information System for the Regional IPM Centers crop profiles. Brackets indicate which state’scrop profile the value was taken from.e.Sweet corn [59,739 seeds/A; 1,800 seeds/lb]f.Southern pea [139,392 seeds/A; 3,200 seeds/lb]g.Based on a maximum of 23,000 seeds planted per acre, weighing 2 ounces per seed (January 28, 2013 letter from National Potato Council).h.Except canolaNA = not applicable NS= not specified

### Fate and Transport Characterization

Environmental Fate Assessment

Environmental transformation of se daxane follows two pathways (see Figure 2 ). Laboratory data indicate that in the environment sedaxane is persistent. Sedaxane is only susceptible to degradation via aerobic soil metabolism. Laborator y half-life values for aerobic soil metabolism are 296-400 (soil) days based on single fi rst order (SFO) kinetics; however, aerobic biodegradation of sedaxane in soil does not follo w single first order kinetics (SFO). In general, sedaxane concentrations decrease over the first 100 days (appr oximate); however, after 100 days, sedaxane concentrations remain steady (approximately 50% of th e applied radioactivity) through study termination ( ≥ 365 days). Additional kinetic analysis using Nth-Order Rate Model or Indeterminate Order Rate Equation ( 

### IORE) and Double First-Order in Parallel (DFOP) models resulted in representative half-l ives >100 days (often >365 days). 3 

### A summary of the kinetic analysis for the aerobic soil meta bolism (MRID 47473448) is provided in APPENDIX A while the results are summarized in Table 5 

### . Sedaxane photolysis studies (l aboratory half-life of 46 days for aqueous photolysis and 253 days for soil photolysis) 4 

### also suggest sedaxane is persistence in the environment. Hydrolysis, anaerobic soil and aquatic transforma tion, and aerobic aquatic metabolism are not expected to contribute to th e dissipation of sedaxane in the environment. Terrestrial field dissipation data (DT 50 

### value 114-132 days) suggest sedaxane will persist in the environment consistent with labora tory metabolism and photolysis data.

Trans - and cis - isomers of sedaxane show comparable degradation rates in soil; however, only a few submitted studies distinguish the two isomers. There is one aerobic soil metabolism study that contains both data for sedaxane degradati on after direct soil application, as well as soil dissipation and transformation data following soil incorporation of sedaxane treated seeds. In addition, the registrant submitted several additional aerobic soil dissipation studies that explored the dissipation of sedaxane after planting of treated seeds. While seed treatment studies represent the intended use pattern and permit the identifi cation of potential enviro nmental transformation products, these studies do not pe rmit the calculation of an aer obic soil metabolism rate (or corresponding half-life values), as ot her dissipation mechanisms may occur [ i.e. , plant uptake in roots or shoots (shoots were analyzed in the submitted studies; however, the roots were analyzed as part of the soil matrix), or chemical sorption to seed coat] wh ich cannot be parsed out due to the study design. In addition, a large amount of unextracted residues further complicates the interpretation of the seed st udies. The amount of unextracted residues increases throughout the study. Despite these complications, these aerobic dissipation/degradation studies suggest that metabolism of sedaxane in soil is faster [laboratory half-life valu es of 88-181 days (seed)] in the presence of germinating seed. This is supported by known literature that describes the influence of plant roots and germinating seeds on mi crobial activity in th e rhizosphere.

3 “ Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media ” Health Canada, U.S. Environmental Protection Agency, December 2011 4 The photolysis half-lives were calculated based on th e assumption that the average daily solar radiation is approximately 75% of the maximum intensity over a 12 hour period. This was taken into account in the comparison of the artificial light source and that of natural summer sunlight, conducted by the study authors. Because solar intensity of natural summer sunlight is likely not 100% during a 12 hour period, and because the sedaxane is proposed as a seed treatment and likely incorporated in the soil, the reviewers did not adjust the half-life values to represent 100% soil radiation over the 12 hour period.NHONNHF2CCH3NHONNHF2CCH3OHNH2ONNHF2CCH3NHONNHF2CCH3HOONHONNHHF2CNHONNHHF2COHOHONNHF2CCH3OHONNHHF2CAMAMAMAMAMAM and PAMAMAM and PAMCO2AMAM and PNHONNHF2CCH3HOHOPNHONNHF2CCH3HOOHOPSedaxane668094210616798670668095667584728931465008Figure 2. Proposed Environmental Transformation Pathwaysfor Sedaxane; Aerobic Metabolism (AM); Photolysis (P);company chemical codes have been shortened(letters have been removed) for brevityMajor (>10%) transformation productMinor (<10%) transformation productTable 5. Chemical Properties and Enviro nmental Fate Parameters of Sedaxane

Parameter Value Source/Classification (Comments)
Selected Physical/Chemical Parameters

Molecular formula C 18 H 19 F 2 N 3 O Calculated using ChemDraw

Molecular weight 331.37 g/mol Calculated using ChemDraw

Vapor pressure 20  C 6.5 x 10 -8 Pa 1.3 x 10 -9 atm 25  C 1.7 x 10 -7 Pa 1.3 x 10 -9 mm Hg

4.9 x 10 -10 atm MRID 47473326

Aqueous solubility at 25  C pH 6.5 14 mg/L MRID 47473326

Henry’s Law Constant calculated based on 14 g/m 3
and 1.7 x 10 -7 Pa at 25  C pH 6.5 4.0 x 10 -6 Pa m 3 /mol 3.95 x 10 -11 atm-m 3 /mol MRID 47473326 Calculated

Log octanol-to-water partition coefficient (log K OW ) at 25°C pH 6.67 3.3 (K OW =2100) MRID 47473326

Dissociation constant (pKa) None (pH 1-12) MRID 47473326

Transformation Mechanisms 1,2
Hydrolysis half-life at 20  C and 50  C No substantial degradation (pH 4, 7, and 9) MRID 47473318/ Acceptable

Aqueous photolysis half-life at 25  C 46 days (identified parent only) MRID 47473319/ Upgradable (up to 20% of the extracted residues were not identified)

Soil photolysis half-life at 20  C 253 days (average value) 213 days (pyrazole-label) 292 days (phenyl-label) MRID 47473446/ Supplemental MRID 47473447/

Supplemental

Aerobic soil metabolism halflife at 20°C 71days (SFO DT50)

IORE DT50= 63 d; DT90= 400 d; tR IORE = 120 d (Gatrenacker loam) extracted parent from seed studies *observed: DT50= 62-84 days DT 90=not observed MRID 47473444/ Supplemental (high application rate; seed treatment)

71 days (SFO DT50) 3 IORE DT50= 44 d; DT90= 883 d; tR IORE = 266 d (Marsillargues silty clay) extracted parent from seed studies *observed: DT50= 27-49 days DT 90=not observed MRID 47473445/ Supplemental (high application rate; seed treatment)

### 11 Parameter Value Source/Classification (Comments)
54 days (SFO DT50) 3 SFO DT50= 64 d; DT90= 212 d; SFO tR = 64 d (Gartenacker loam) extracted parent from seed studies *observed: DT50= 27-81 days DT 90=123-365 78 days (SFO DT50) SFO DT50= 78 d; DT90= 258 d; SFO tR = 78 d (Paperlacker loamy sand) extracted parent from seed studies *observed: DT50= 27-81 days DT 90=not observed

95 (SFO DT50) IORE DT50= 83 d; DT90= 8504 d; tR IORE = 2560 d (18 acres sandy clay)

extracted parent from seed studies *observed: DT50= 81-123 days DT 90=not observed 87 days (SFO DT50) SFO DT50= 87 d; DT90= 288 d; SFO tR = 78 d Gartenacker loam) extracted parent from seed studies *observed: DT50= 31-50 days DT 90=237-365

MRID 47473448/ Supplemental [high application rate; high levels of unextracted residues; some studieswere conducted on treated seeds; halflife values are calculated well beyond the study termination (up to 365 days)] 78 days (SFO DT50) IORE DT50= 34 d; DT90= 3763 d; tR IORE = 1130 d (California sand) extracted parent from seed studies *observed: DT50= 31-81 days DT 90=not observed 133 days [average of 105 (SFO DT50; phenyl) and 160 (SFO DT50; pyrazole) days]

DFOP DT50= 49 d; DT90= 894 d; DFOP Slow t 1/2 = 373 d (North Dakota clay loam, pyrazole) extracted parent from seed studies *observed: DT50= 80-122 days DT 90=not observed

DFOP DT50= 42.4 d; DT90= 1094 d; DFOP Slow t 1/2 = 544 d (North Dakota clay loam, phenyl) extracted parent from seed studies *observed: DT50= 31-50 days DT 90=not observed

tR DFOP Slow t 1/2 = 459 d (average of both labels)

296 days (SFO DT50) DFOP DT50= 222 d; DT90= 3005 d; DFOP Slow t 1/2 = 1200 d (Gartenacker loam) extracted parent from soil studies *observed: DT50= 241-367 days DT 90=not observed

### 12 Parameter Value Source/Classification (Comments)

373 days (SFO DT50) 3 DFOP DT50= 423 d; DT90= 3376 d; DFOP Slow t 1/2 = 1270 d (California sand) extracted parent from soil studies *observed: DT50= 241->367 days DT 90=not observed

400 days [average of 422 (SFO DT50;phenyl) and 377 (SFO DT50;pyrazole) days]

DFOP DT50= 98 d; DT90= >>365 d; DFOP Slow t 1/2 = 1280 d (North Dakota clay loam, pyrazole) extracted parent from soil studies *observed: DT50= 80-122 days DT 90=not observed

DFOP DT50= 437 d; DT90= 2306 d; DFOP Slow t 1/2 = 805 d (North Dakota clay loam, phenyl) extracted parent from soil studies *observed: DT50= 241-367 days DT 90=not observed

tR DFOP Slow t 1/2 = 1043 d (average of both labels)

Aerobic aquatic metabolism half-life (20  C) 849 (river; SFO DT50) and 920 (pond; SFO DT50) days (whole system) MRID 47473468/ Supplemental [high application rate; >10% applied radioactivity present as unextracted residues; half-life values are calculated well beyond the study termination (360 days)]

Anaerobic soil metabolism half-life (20  C) 375 days **dissipation half-life of extracted parent from seed studies ** MRID 47473443/ Supplemental [high application rate; >10% applied radioactivity present as unextracted

residues; study was conducted on treated seeds; half-life values are calculated well beyond the study termination (123 days)]

Anaerobic aquatic metabolism half-life (20  C) 4693 (river; SFO DT50) and 1970 (pond; SFO DT50) days (whole system) MRID 47473468/ Supplemental [high application rate; >10% applied radioactivity present as unextracted residues; half-life values are calculated well beyond the study termination (360 days)] Mobility Range of Freundlich soil-water

partition coefficients (K F ); 1/n value; andFreundlich organic carbonnormalized coefficients (K FOC ) 6.7, 2.8, 16.3, 3.1, 2.0, and 12.9 L/kg-soil; 0.81, 0.85, 0.90, 0.92, 0.87, and 0.83; and 256.6, 268.5, 587.5, 584.9, 662.5, and 528.9 mL/g OC MRID 47473461/ Acceptable

### 13 Parameter Value Source/Classification (Comments)
Field Dissipation

Terrestrial field dissipation half-life Washington loamy sand: 31 days North Dakota sandy loam: 95 days California sandy loam: 31 days ( seed studies ) MRID 47473453/ Supplemental Washington loamy sand (in furrow 1.5 g/ha): 119 days Washington loamy sand (in furrow 91 g/ha): 132 days ( soil studies ) France silt loam: 119 days Italy silty clay loam: 131 days ( seed studies ) MRID 47473454/ Supplemental

1. Reported half-life values used in this assessment we re calculated using the draft NAFTA degradation kinetics 

### 3 ; Single First Order (SFO), Nth-Order Rate Model or Indeterminate Order Rate Equation Model (IORE), and Double First-Order in Parallel (DFOP); Representative ha lf-life to be used to calculate model input value for IORE (tR IORE ). Values reported in the new chemical assessment are shown in italic . At the time of the new chemical a ssessment half-life values provided were based on single first order (SFO) rates that may not have represented the “best” fit or representative kinetic model for degradation. Selected representa tive half-life values are shown in bold

. 2. Reported half-life values are for total extracted sedaxane residues [(SYN524464) or SYN508210 (trans-isomer of sedaxane) and SYN508211 (cis-isomer of sedaxane) combined]. 3. Value was incorrectly reported in new chemical assessment.



### As mentioned above, a large amount of unextracted residues were observe d in the soil studies (up to 42% of the applied radioa ctivity). At least twice as much unextracted radioactivity was observed in some of the seed treatment studies. It is unclear if these residues are non-extracted residues or bound residues, or in th e case of the seed stud ies, residues sorbed to the seed coat or taken up by the roots (only shoots were examined separately from the soil). The extraction method employed in these studies was not verified for soil aged sedaxane residues or the transformation products. Furthermore, the uses of different extraction systems (different solvents) were not explored in the submitted st udies. Therefore, it cannot be determined if another solvent system may have been better suited for these studies.

The application rates used in all the submitted aerobic metabolism (seed and soil) studies are much higher (>15X) than the maximum seed treatm ent application rates fo r barley, canola, oat, rye, soybean, triticale, and wheat. For some chem icals, the application rate has been shown to alter the degradation rate. For example, high application rates may adversely impact the microbial activity within a soil decreasing metabolism and limiting the potential identification of transformation products. The microbial activity of the treated soils was also not reported in the submitted studies; therefore, it cannot be determ ined if the soil remained active throughout the study.

Sedaxane is moderately mobile (mean K F 

### of and mean 7.3 L/kg-soil; 1/n ranged from 0.81-0.92; mean K FOC 

### of 481 L/kg OC 

### ; n=6). The leaching potential of sedaxane through soil is correlated with the organic carbon fraction of the soil. Based on the K OW 

### (log K OW 

### = 3.3) for sedaxane, it is not expected to bioaccumulate in aquatic and terrestria l organisms. A fish bioconcentration study confirms that accumulation does not occur. Seda xane is nonvolatile and volatilization is not expected to be a route of dissipati on for sedaxane in the environment.

### 14 Under conditions conductive to de gradation (aerobic soil metabolism and photolysis), sedaxane has been shown to form five major transf ormation products, includi ng carbon dioxide. The anticipated transformation pathway along with the chemical structures of each of the transformation products are presented in Figure 2 . Two of the major transformation products, CDCD668094 and CDCD668095, retain both the pyrazole and the phenyl ring moieties. Both of these transformation products were observed in aquatic photolysis expe riments conducted with natural water. Two other products, CSCD 465008 and CSAA798670, are pyrazole ring amide cleavage products with and without the N-methyl group, respectively. Both of these transformation products were observed under aerobic soil conditions, while only CSAA798670 was observed in photodegradation studies. Table 6 provides the maximum observed concentrations of each of the sedaxane tran sformation products identified in the submitted environmental fate studies. Several other minor degradation products were observed in the degradation studies including: CS CC210616, CSCD728931 and CSCD667584. A number of other minor transformation products were not identified in the submitted studies.

Table 6. Maximum Observed Concentrations of Each of the Sedaxane Transformation Products

Code Name/

Synonym Study Type MRID/ Classification Maximum Percent

of Applied (interval)

Major

CSCD465008

R958945 Aerobic Soil Metabolism

835.4100 47473448/ Supplemental 32.76 (237 days; North Dakota seed)

CSAA798670 SYN449410 NOA449410 Aerobic Soil Metabolism

835.4100 47473448 Supplemental 15.37 (367 days; California soil)
Aqueous Photolysis 835.2240 47473319/ Upgradable 25.69 (28 days; natural water)

CSCD668094 Aqueous Photolysis 835.2240 47473319/ Upgradable 16.66 (28 days; natural water)

CSCD668095 Aqueous Photolysis 835.2240 47473319/ Upgradable 18.09 (28 days; natural water)

Minor

CSCD667584 Aerobic Soil Metabolism

835.4100 47473445 Supplemental 4.9 (81 days; Gartenacker seed)

CSCC210616 SYN508272 Aerobic Soil Metabolism

835.4100 47473448/ Supplemental 2.98 (367 days; California soil)

Aqueous Photolysis 835.2240 47473319/ Upgradable 5.42 (28 days; natural water)

### 15 Code Name/

Synonym Study Type MRID/ Classification Maximum Percent

of Applied (interval)

Major

CSCD728931 Aerobic Soil Metabolism

835.4100 47473448/ Supplemental 7.91 (241 days; California soil)



### Aerobic soil metabolism data were provided fo r the sedaxane environmental transformation product CSCD465008, as well as adsorption/deso rption data. These data indicate that CSCD465008 may be persistent to aerobic soil metabolism (half-lif e values range from 40 to 157 days) in the environment. Mobility data suggest that CSCD465008 is highly mobile in soil (mean K FOC 

### of 0.04 L/kg; 1/n ranged from 0.73-1.0; and mean K OC 

### 2 mL/g; n=3). These data are summarized in Table 7 . The registrant recently submitted tw o studies environmental fate studies (MRIDs 48836611 and 48836612). These studies are currently under revi ew; however, the results of this review are not e xpected to have any impact on this assessment as the test materials used in these two studies are not considered as residues of concern by the Health Effects Division.

Table 7. Chemical Properties and Environmental Fa te Parameters of CSCD4 65008 an Environmental Transformation Product of Sedaxane

Parameter Value Source/ Classification
Selected Physical/Chemical Parameters

Molecular formula C 5 H 4 F 2 N 2 O 2 Calculated using ChemDraw

Molecular weight 162.10 g/mol Calculated using ChemDraw

Vapor pressure 2.0 x 10 -4 mmHg EpiWeb 4 (modified Grain method)

Aqueous solubility at 25  C 20 g/L EpiWeb 4 (Wat Sol (v1.01 est)

Henry’s Law Constant 25  C 3.3 x 10 -5 Pa m 3 /mol 2.0 x 10 -10 atm-m 3 /mol Log octanol-to-water partition coefficient (log K O W ) 0.30 EpiWeb 4 (KOWWIN v1.67 estimate)

Transformation Mechanisms 1

Aerobic soil metabolism half-life at 20°C Marsillargues silty clay: 324 days Gartenacker loam: 266 days 18 acres sandy clay: 168 47473451/ Supplemental (high application rate)

### 16 Parameter Value Source/ Classification
Marsillargues silty clay: 157 days Gartenacker loam: 99 days 18 acres sandy clay: 40 (extracted 5008 from soil studies) 47473452/ Supplemental (high application rate)

Mobility Range of Freundlich soil-water partition coefficients (K F ); 1/n value; Freundlich organic carbon-norma lized coefficients (K FOC ) 0.013, 0.02, and 0.10 L/kg-soil; 0.73, 0.96, and 1.0; 0.55, 1.89, and 3.59 mL/g OC 47473463/ Supplemental

1. The half-life values provided are based on single first order (SFO) rates and may not represent the “best” fit kinetic model for degradation. The aerobic soil me tabolism of sedaxane does not follow single first order kinetics in the submitted studies. IORE and DFOP half-life values were also calculated following the draft NAFTA guidance: Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media (see Appendix A ).



### Conceptual Model

Possible routes of dissipation of pesticides including sedaxane and its environmental transformation products are illustrated in Figure 3 . While sedaxane is a seed treatment with relatively low application rates (maximum single application rate currently registered 0.008 lb a.i./a; maximum single applicati on rate proposed 0.1 lb a.i./A), it is persistent. Data suggest sedaxane is susceptible to degr adation via aerobic so il and photolysis. Sedaxane may leach to groundwater or may move to surface water bodies via runoff of dissolv ed or soil sorbed residues.

Figure 3. Probable Routes of Pestic ide Dissipation in the Environment

Drinking Water Exposure Modeling

Since the new chemical assessment was comp leted, the Health Effects Division’s (HED) Residues of Concern Knowledgebase Subcommi ttee (ROCKS) reevaluated the residues of concern considered in the human health asse ssment. ROCKS determined that CSCD465008 and CSAA798670 are no longer considered residues of concern based on recently submitted toxicity

### 17 data. 5 

### Therefore, the residues of concern for the human health assessment are sedaxane (SYN524464), a mixture of two isomers separately numbered SYN508210 ( trans -isomer of sedaxane) and SYN508211 ( cis -isomer of sedaxane) and two known environmental transformation products of equal toxicol ogical concern, CDCD668094 and CDCD668095. These compounds are referred to collectively as tota l toxic sedaxane residues (TTSR). Both CSCD465008 and CSAA798670 were only observed to form in the aquatic photolysis studies; therefore, since aquatic photolys is is not considered as part of the groundwater modeling approach, TTSR are only considered in surface water modeling.

This DWA includes estimated drinking water con centrations (EDWCs) based on Tier I surface water and Tier I groundwater model simulati ons for all the proposed sedaxane uses.

Models

As part of PRZM-Groundwater (PRZM-GW version 1.0, December 11, 2012) the implementation phase, Tier I groundwater EDWCs are derived using both SCI-GROW (Screening Concentration in Groundwater, ve rsion 2.3, August 8, 2003) and PRZM-GW using the GW-GUI (Graphical User Interf ace, version 1.0, December 11, 2012).

SCI-GROW is an empirical model based on a linear best fit of 13 prospective groundwater studies (one year of application) . SCI-GROW was designed solely for use as a Tier I screening tool and does not have the capability to consider mitigating circumstances such as variability in leac hing potential of diff erent soils, weather (including rainfall), depth to aquifer, nor doe s it consider multiple years of application.

PRZM-GW is a one-dimensional, finite-di fference model that estimates the concentrations of pesticides in groundwater. It accounts for pe sticide fate in the crop root zone by simulating pesticide transport and de gradation through the soil profile after a pesticide is applied to an agricultural field. PRZM-GW permits the assessment of multiple years of pesticide application (up to 100 years) on a single site. Six standard scenarios, each representing a different re gion known to be vulnerable to groundwater contaminations, are availabl e for use with PRZM-GW for ri sk assessment purposes. In PRZM-GW simulations, each of these standard scenario s was used. PRZM-GW output values represent pesticide concentrations in a vulnerable groundwater supply that is located directly beneath a rural agricultural field.

The PRZM scenarios used in gr oundwater simulations are repres entative of vulnerable sites— shallow unconfined aquifers under an agricultu ral field with leaching prone soil—and output values represent pesticide concentrations that may be observed in drinking water resulting from the use of groundwater vulnerable to pesticide contamination as source water. The results are expected to represent the upper bound values on the concentrati ons of sedaxane that may be found in drinking water supplied by groundwater. The PRZM-GW conceptual model has been reviewed by two different Fe deral Insecticide, Fungicide, and Rodenticide Act (FIFRA)

5 U.S. Environmental Protection Agency, Holman, E. Sedaxane Seed treatment Drinking Water Revisit. Report of the Residues of Concern Knowledgebase Subcommittee Dec. 19, 2012, PC Code: 129223; DP 406945

### 18 Scientific Advisory Panels (SAP) and recommende d for implementation as a risk assessment tool in OPP. 6,7



### Tier I surface water EDWCs resulti ng from the proposed uses of se daxane were calculated using FQPA Index Reservoir Screening Tool (FIRST) model. The defau lt percent cropped area (PCA) value of 91% for non-turf uses is used in th is assessment to account for the sedaxane use on multiple crops. The PRZM scenario used for FIRST development was among the most vulnerable, and thus resulting su rface water concentra tions that represent the upper bound values on the concentrations that might be found in drinking water from the use of sedaxane.

FIRST is a metamodel of PRZM (P esticide R oot Z one M odel, version 3.12.3, June 2006) and EXAMS (EX posure A nalysis M odeling S ystem, version 2.98.04.06, April 2005) models. PRZM is used to simulate pesticide transport as a result of runoff and erosion from an agricultural field. EXAMS estimates environmental fate and transport of pesticides in surface water for an index reservoir. FIRST was developed by making multiple runs of PRZM using varying sorption coefficients and determining the concentration in the EXAMS index reservoir scen ario after a two-inch single storm event. The single runoff event moves a maximum of 8% of the applied pesticide into the reservoir. This amount can be reduced by degr adation or effects of binding to soil in the field. Additionally, FIRST can account for sp ray drift and adjusts for the area within a watershed that is planted with the modeled crop.

Modeling Approach and Input Parameters

No data are available on the amount of sedaxane that may come off a treated seed once it is planted; therefore, in all model runs 100% of sedaxane applied to the treated seed is assumed to be available for runoff and leaching in the form of sedaxane or total toxic sedaxane residues.

Uncertainties exist in choosing i nput parameters. For this reason, th is assessment incorporates all scientifically available data to conservatively and reasonably estimate sedaxane residue levels resulting from the proposed uses. The input parameters used in th is DWA are selected from the environmental fate data submitted by the regist rant in accordance with US EPA-OPP EFED water model parameter guidance. 8



### The half-life values used in aquatic modeling for sedaxane have been updated and are consistent with the NAFTA guidance: Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media. As mentioned in the fate and transp ort section of this document, aerobic biodegradation of sedaxane in soil does not follow single first order kinetics. In general, sedaxane concentrations decrease over the first 100 days (appr oximate); however, after 100 days,

6U.S. Environmental Protection Agency. Federal Insecticid e, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel: N-Methyl Carbamat e Pesticide Cumulative Risk Assessment: Pilot Cumulative Analysis, February 15-18, 2005 , 2005-01, Docket Number: OPP-2004-0405. 7 U.S. Environmental Protection Agency. Federal Insecticid e, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel: Preliminary N-Methyl Ca rbamate Cumulative Risk Assessment, August 23-26, 2005 , 2005-04, Docket Number: OPP-2005-0172.

8 Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides , Version 2.1, October 22, 2009.

### 19 sedaxane concentrations remain steady (approximately 50% of th e applied radioactivity) through study termination ( ≥ 365 days).

The input parameters used in the groundwater and surface water analysis are provided in the subsections below.

Groundwater

Input values used in the model runs for SCI-G ROW are summarized in Table 8 . Rationale for choosing each input parameter is discussed in the subsection below the table. Application scenarios model used SCI-GROW are summarized in Table 9

.

Table 8. Input Parameters Used in SCI-GROW Modeling to Estimate Sedaxane Concentrations Resulting From the Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; Except Soybean), Rapeseed (Subgroup 20A), and Potato

Input Parameter

(Symbol; Unit) Value for Sedaxane (parent only) Reference Comment

Aerobic Soil (t 1/2 ; days)] 1298 days 47473448/ Supplemental Input value used in previous assessment was based on SFO kinetics (415 days). This value was derived from soil studies only. Representative half-life values used to derive the model input value used in this assessment were developed following the NAFTA kinetics guidance. Average Soil Partition Coefficient K foc = 557 mL/g K oc = 623 mL/g 47473461/ acceptable

Table 9. SCI-GROW Representative Application Scenarios

Use Number of Applications/

Application Rate

(lb a.i./A)

corn 2/0.02

sorghum 2/0.005

dried shelled pea and bean 2/0.002

rapeseed 2/0.0003

potato 1/0.1

corn-wheat rotation 1/0.01 and 1/0.008

### 20 Aerobic Soil Metabolism Half-life

The registrant provided aerobic so il metabolism data for sedaxane in three different soils (MRID 47473448).

The rate constant for disappearance of extr actable sedaxane residues was calculated for four different experiments at 20 °C. The diffe rence in the two studies was the position of the radiolabel; therefore, a representativ e half-life for the North Dakota soil was calculated by averaging the two half-life valu es. The representative half-lives calculated ranged from 459-1270 days. The observed DT50 values ranged from 222-423; however, DT90 values ranged from 2306-3005 days. This indicates a substa ntial decrease in transformation over time. Two of the four re ported half-live values were derived from the same soil (North Dakota sandy clay loam). The upper 90 th 

### percentile confidence bound on the mean half-life value for sedaxane fr om the three soils was determined to be 1298 days [1171 (average of 1043, 1200, and 1270) + (1.886 x 116)/ √ 3].

Note: As stated earlier there is a large am ount of unextracted residues in both of the aerobic soil metabolism studies. Additional data should be provid ed by the registrant to confirm that the unextracted residue is not sedaxane or a degradate of toxicological

concern.

Soil Partition Coefficient

The registrant provided adsorp tion/desorption data necessary to determine parameters, K d 

### and K f 

### for adsorption of sedaxa ne (MRID 47473461) to soil.

Analysis of sedaxane adsorption data showed that the Freundlich 1/n value ranged from 0.81-0.90 indicating that sorption is slightly nonlinear. Soil adsorption of sedaxane was shown to correlate with the organic carbon c ontent (i.e. the coefficient of variation for K oc 

### and K foc 

### values are less than that for K d 

### and K f 

### values) of the soil. K foc 

### values for sedaxane ranged from 257-662 mL/g with a median value of 557 mL/g (mean value of 481 mL/g). K oc 

### values for sedaxane ranged from 290- 728 mL/g with a median value of 623 mL/g (mean value of 537 mL/g).

Groundwater analysis was completed using PRZM-GW. Input values used in the model runs for PRZM-GW are summarized in Table 10 . Standard scenarios, applica tion interval, and data of the first application are provided in Table 11 . Rationale for choosing each input parameter is provided in the subsections below.

Table 10. Input Parameters Used in PRZM-GW Modeling to Estimate Sedaxane Concentrations Resulting From the Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; Except Soybean), Rapeseed (Subgroup 20A), and Potato

Input Parameter

(Symbol; Unit) Value for Sedaxane (parent only) Reference Comment

Hydrolysis (t 1/2 ; days)] 0 47473318/ Acceptable

### 21 Aerobic Soil (t 1/2 ; days)] 1298 days 47473448/ Supplemental Previous input value used based on SFO kinetics is 415 days. Value derived from soil studies only. Representative half-life values used to derive the model input value were developed following the NAFTA kinetics guidance. Average Soil Partition Coefficient K foc = 481 mL/g K oc = 537mL/g 47473461/ acceptable

### 22 Table 11. PRZM-GW Representative Model Scenarios

Use Number of Applications/

Application Rate

(kg a.i./ha) Interval Between Applications (days) Application Date(s) Scenario/

Weather

corn a 2/0.02 30 or 138 4/30 and 5/30 or 9/15 NC Eastern Coastal Plain/ W13722

WI Central Sands/ W14920

Delmarva/ W13781

GA Coastal Plain/ W93805

FL Central Ridge/ W12842

FL Jacksonville/ W13889 sorghum 2/0.005 138 4/30 9/15
dried shelled pea and bean 2/0.002 138 4/30 9/15

rapeseed 2/0.0003 138 4/30 9/15

potato 1/0.09 NA 4/30

corn-wheat rotation 1/0.02 and 1/0.008 138 4/30 9/15

a. Since the highest single application is for corn and it can be reapplied after crop failure it is the only scenario modeled. na = not applicable



### Hydrolysis

The registrant provided the hydrolysis da ta for sedaxane (MRID 47473318). These data suggest that sedaxane is stab le to hydrolysis over a range of pHs as well as elevated temperatures.

Aerobic Soil Metabolism Half-life

See model input value selection for SCI-GROW.

Soil Partition Coefficient

A discussion of the experimental results is provided in the model input values for SCIGROW. The mean K foc 

### value was used according to input parameter guidance for sedaxane.

Surface Water

Input values used in FIRST (PRZM-E XAMS) model runs are summarized in Table 12

. Rationale for choosing each input parameter is provided in the subsections below. The input

### 23 values used in groundwater simulations are the sa me as those used in surface water simulations for hydrolysis, aerobic soil metabolism, and sorp tion; therefore, rati onale for these input parameters are not reported in this section. Th e input value used for aquatic photolysis was recalculated for total toxic sedaxane based on the recent ROCKS decision5. No spray drift was considered in the model runs (assumed granular application) since sedaxane is expected to be dried to the surface of the seed co at when the seed is planted. In addition, since the incorporation depth of each plated seed varies between crops, a quick screen th at assumed no soil incorporation was completed.

Table 12. Input Parameters Used in FIRST (PRZM-EXAM S) Modeling to Estimate Sedaxane and Total Toxic Sedaxane Residue Concentrations Resulting From the Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; Except Soybea n), Rapeseed (Subgroup 20A), and Potato

Input Parameter

(Symbol; Unit) Value for Sedaxane Comment Reference/

Classification

Molecular Weight 331.37 g/mol Parent value Calculated using ChemDraw
Henry’s constant (25 o C) 3.95 x 10 -11

atm-m 3 /mol Parent value MRID 47473326 Calculated

Vapor Pressure (torr) 1.3 x 10 -9 25 °C 4.9 x 10 -9 20 °C Parent value; only empirical data available for sedaxane 47473326

Solubility in Water (g/L at 20 o C) 14 mg/L Parent value 47473326
Hydrolysis Half-life (t 1/2 at pH 7) 0, stable Parent value 47473318/ AcceptableAquatic Photolysis Halflife (days; t 1/2 at pH 7) 54 1 Value for TTR 47473319/ Upgradable

Aerobic Soil Metabolism [upper 90 th percentile confidence bound on the mean half-life value (t 1/2 ; days)] 1298 Parent value Unidentified/unextracted material made up >>10% of the applied radio activity at any

point during the

experiment. 47473448/ Supplemental

Aerobic Aquatic Metabolism Half-life [water column; upper 90 th percentile confidencebound on the mean halflife value (t 1/2 ; days)] 994 Parent value Unidentified material made up <10% of the applied radio activity at

any point during the experiment. 47473468/ Supplemental

Anaerobic Aquatic Metabolism Half-life [benthic; upper 90 th percentile confidencebound on the mean halflife value (t 1/2 ; days)] 7522 Parent value Unidentified material made up <10% of the applied radio activity at

any point during the experiment. 47473468/ Supplemental

Average Soil Partition Coefficient (K oc ; mL/g) K foc = 481 mL/g K oc = 723 mL/g 47473461/ Acceptable

### 24 Gray shading indicates data is not considered in FIRST; however, PRZM-EXAMS modeling incorporates such data so it is provided for completeness. 1. Dark control-adjusted (rate of i rradiated – rate of non-irradiated ) as well as adjusted to a 12- hour/day photoperiod at 40 °N latitude. The ar tificial light source used in this experiment was determined to be equivalent to 0.9 days at 40 °N latitude.

### 25 Aquatic Photolysis Half-life

The registrant provided aquatic photolysis data for sedaxane in buffered solution as well as in natural water (MRID 47473319). Only th e results for the buffered solution were used for modeling purposes. The rate constant for disappearance of ex tractable total toxic sedaxane residues was calcul ated using pyrazole-labeled sedaxane data, as the two additional residues of concern bot h retain the pyrazole moiety.

Up to 20% of the extracted residues were not identified in the submitted aqueous photolysis study. Confirmation that these uni dentified residues are not sedaxane, a transformation of toxicological concern, or a transformation product that reaches a concentration greater than 10% of the applie d material during the course of the study should be provided.

Aerobic Aquatic Metabolism Half-life

The registrant provided data on the aerobic aquatic degr adation of sedaxane. The formation of several unknown transformation products (accounting for <10% of the radioactivity) was observed; however, none of these produc ts were identified. The 90 th 

### percentile confidence b ound on the mean total toxic sedaxane half-life value is 994 days= (average of 849 and 920) + [(3.078 x 50.2)/ √ 2)]. These studies did not report the formation of the two sedaxane transforma tion products of toxicological concern.

Aerobic Aquatic Metabolism Half-life

The registrant provided data on the anaerobi c aquatic degradation of sedaxane. The formation of several unknown transformation products (accounting for <10% of the radioactivity) was observed; however, none of these produc ts were identified. The 90 th 

### percentile confidence b ound on the mean total toxic sedaxane half-life value is 994 days= (average of 4693 and 1970) + [(3.078 x 50.2)/ √ 2)]. These studies did not report the formation of the two sedaxane transforma tion products of toxicological concern.

Groundwater

PRZM-GW Tier I groundwater EDWC s for sedaxane resulting from the proposed sedaxane uses on corn, sorghum, dried shelled pea and b ean (Subgroup 6C; except soybean), rapeseed (subgroup 20A), and potato are highlighted in Table 13 . The PRZM-GW estimates are higher than those calculated using SCI-GROW ( Table 166 ); therefore, PRZM-GW EDWCs are the Tier I groundwater estimates recommended for use in the human health risk assessment. Peak and post breakthrough average EDWCs in groundwater resulting from the proposed sedaxane uses are not expected to be > 22.4 μ g/L and 19.3 μ g/L, respectively. These estimates were derived based on the proposed potato use. Depending on the scenario simulated, the EDWCs range from 3.6 μ g/L to 22.4 μ g/L and 3.5 to 19.3 μ g/L for peak and post breakthrough concentrations, respectively. Model outputs indi cate that the time to breakthrough (the time it takes for sedaxane residues to reach the underground aquifer) ranges from 3811-10,389 days depending on the scenario. With the exception of potato, this analys is is based on 30 years of sedaxane use as a

### 26 seed treatment with two plantings per year. So me of the model output files are provided in APPENDIX D

.

Table 13. Tier I PRZM-GW EDWCs for Sedaxane From the Proposed Uses Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; Except Soybean), Rapeseed (Subgroup 20A), and Potato

Crop Sedaxane Scenario Peak (μg/L) Post-Breakthrough Average (μg/L) Days to Breakthrough

corn 9.9 8.4 9547 WI Central Sands

2.5 2.1 8328 GA Coastal Plain

7.2 6.3 4973 NC Eastern Coastal Plain

5.8 5.3 3811 Delmarva

6.1 5.5 4164 FL Central Ridge

1.6 1.6 10,389 FL Jacksonville

sorghum 2.5 2.1 9547 WI Central Sands

0.6 0.5 8328 GA Coastal Plain

1.8 1.6 4973 NC Eastern Coastal Plain

1.5 1.4 3811 Delmarva

1.6 1.4 4164 FL Central Ridge

0.4 0.4 10,389 FL Jacksonville

dried shelled pea and bean (subgroup 6C; Except Soybean) 1.0 0.8 9547 WI Central Sands

0.3 0.2 8328 GA Coastal Plain

0.7 0.6 4973 NC Eastern Coastal Plain

0.6 0.5 3811 Delmarva

0.6 0.5 4164 FL Central Ridge

0.2 0.2 10,389 FL Jacksonville

rapeseed (subgroup 20A) 0.1 0.1 9547 WI Central Sands

0.04 0.03 8328 GA Coastal Plain

0.1 0.09 4973 NC Eastern Coastal Plain

0.09 0.08 3811 Delmarva

0.09 0.08 4164 FL Central Ridge

0.02 0.02 10,389 FL Jacksonville

### 27 potato 1 22.4 19.3 9547 WI Central Sands

5.8 4.9 8328 GA Coastal Plain

16.0 13.9 4973 NC Eastern Coastal Plain

12.9 11.7 3811 Delmarva

13.7 12.4 4164 FL Central Ridge

3.6 3.5 10,389 FL Jacksonville

corn-wheat rotation 6.9 6.0 9547 WI Central Sands

1.8 1.5 8328 GA Coastal Plain

5.0 4.4 4973 NC Eastern Coastal Plain

4.0 3.7 3811 Delmarva

4.3 3.8 4164 FL Central Ridge

1.1 1.1 10,389 FL Jacksonville

Bold font indicates highest value 1- One application of sedaxane every year @ 0,1 kg/ha



### As part of a Tier II analysis , PRZM-GW was used to examine the impact of the organic carbon content of the top layer of soil (20 cm) on the potato EDWCs. These analyses were completed for the Wisconsin Central Sands scenarios since it provides the most conservative Tier I EDWCs as well as for Delmarva and North Carolina East ern Coastal Plain scenar ios as these scenarios are thought to reasonably represent potato grow ing regions with groundwat er supplies vulnerable to contamination via pesticide leaching. The results of these anal yses are provided in Table 14

.

### 28 Table 14. Organic Carbon Soil Content Analysis

Organic Carbon Content of the Top

Layer of Soil a 

### Sedaxane Scenario Peak (μg/L) Post-Breakthrough Average (μg/L) Days to Breakthrough

0.5% 22.1 19.1 8630 WI Central Sands

16.6 14.4 4521 NC Eastern Coastal Plain 12.9 11.8 4160 Delmarva

1% 18.3 15.9 9448 WI Central Sands

14.2 12 6443 NC Eastern Coastal Plain 11.6 10.5 4515 Delmarva

1.5% 14.8 13.7 10340 WI Central Sands

12.2 10.3 8404 NC Eastern Coastal Plain 10.4 9.4 4869 Delmarva

2% 19.4 b 17.7 b 11258 b WI Central Sands 17.8 6.8 11258 c

10.4 9.2 10340 NC Eastern Coastal Plain 9.4 8.4 5201 Delmarva

3% 14.8 b 13.9 b 13013 b WI Central Sands

8.2 b 7.5 b 14350 b NC Eastern Coastal Plain 7.6 7.0 5867 Delmarva



### a. 20 cm 

### b. extended weather file used; 10 0 year simulation with 100 years of repeated applications



### c. extended weather file used; 10 0 year simulation with 30 year s of repeated applications



### Essentially, this analysis shows that increasing the amount of organic carbon content in the top layer of the soil (increased hold up) allows for increased degrada tion of sedaxane and reduces the EDWCs. Examination of the potential impact of well setbacks and increa sed depth to aquifer were not pursued, as increasing the pesticide tr ansport time in the layers of the soil where minimal degradation is expected will only delay the time to breakthrough and have little impact on the EDWCs based on the model half-life value.

Another assessment was conducted to evaluate the impact of a sedaxane application (0.1 kg/ha) every other year in the potato growing regions (Table 15). Al l scenarios except the Wisconsin Central Sands scenarios have post breakthrough av erage sedaxane concentrations less than 10 μg/L. The average time breakthr ough time for sedaxane occurrence in ground water ranged from 4164 to 10,346 days.

### 29 Table 155. PRXM GW EDWCs for a Single Sedaxa ne Application Every Other Year on Potato Scenario Peak (μg/L) Post-Breakthrough Average

(μg/L) Breakthrough Time (days) Wisconsin Central Sands 15.1 13 8593 a Florida Citrus 6.85 6.24 4164 Florida Potato 2.06 1.92 10346 a Delmarva 6.59 6.00 4186 NC Coastal Plain 8.09 6.95 4957 GA Coastal Plain 3.77 3.4 8800 a a-Model simulation was conducted using a 100 year weather file.

Table 166. Tier I SCI-GROW Grou ndwater EDWCs for Sedaxane From the Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; Except Soybean), Rapeseed (Subgroup 20A), and Potato

Crop Sedaxane Peak

(μg/L)

corn 0.05

sorghum 0.01

dried shelled pea and bean 0.05

rapeseed 0.0008

potato 0.1

corn-wheat rotation 0.02

Bold font indicates highest value


### These groundwater EDWCs generated using PRZM-G W are expected to be conservative based on the assumption that all the sedaxane appl ied to a seed is available for leaching.

Based on HED’s estimated level of concern, limiting sedaxane use in areas known to be vulnerable to groundwater contamination is reas onable, given the range of EDWCs calculated using the various scenarios in modeling. Specifically, for potatoes some of the less vulnerable of the vulnerable scenarios result in peak and post breakthrough concentrations of 3.6 μ g/L and 3.5
μ g/L, respectively.

Surface Water

Tier I surface water EDWCs for sedaxane resulting from the proposed uses on barley, corn, sorghum, dried shelled pea and bean (Subgroup 6C ; except soybean), rape seed (subgroup 20A), and potato are listed in Table 17 . The model output files are provided in APPENDIX C

. Sedaxane EDWCs resulting from sedaxane use as a seed treatment on potato once a year provide the most conservative Tier I surface water EDWC s; however, these values are less than those

### 30 estimated for groundwater using PRZM-GW. Therefore, PRZM-GW groundwater EDWCs are recommended for use in the Human Health Risk Assessment.

Table 17. Tier I Surface Water PCA Corrected EDWCs fo r Sedaxane from the Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; Except Soybean), Rapeseed (Subgroup 20A), and Potato

Crop Total Toxic Sedaxane Residues Peak EDWC

μ g/L (ppb) Yearly Mean
μ g/L (ppb) corn 2.0 0.6 sorghum 0.5 0.1 dried shelled pea and bean (subgroup 6C; Except Soybean) 0.2 0.06

rapeseed (subgroup 20A) 0.03 0.009

Potato 4.1 1.2 Bold font indicates highest value



### Monitoring Data

No monitoring data are available at this time, as sedaxane was only recently registered in the United States.

Assumptions and Limitations

In all model runs, all the sedaxa ne applied to treated seeds wa s assumed to be available for runoff and leaching. In reality, not all the applied sedaxane will leach from the seed coat to the surrounding soil. Some of the sedaxane may be ta ken up by the spouting seed while some of the sedaxane may remain sorbed to the seed coat. This assumption likely results in EDWCs that are conservative.

In the aquatic photolysis study some of the samp les have up to 20% extracted residues that are not identified. These residues could be sedaxa ne or a transformation product that is of toxicological concern. The unidentif ied residues were not consider ed when calculating the halflife values or corresponding modeling input values for sedaxane. Additional data are needed to confirm that these unidentified residues ar e not sedaxane, a transformation product of toxicological concern or a transf ormation product that reaches c oncentrations greater than 10% of the applied radioactivity. Si nce the EDWCs for groundwater are higher than those for surface water where aquatic photolysis half-life is a mode l input value, the incl usion of the up to 20% unidentified residues in the model input calculations is not likely to substantially change the reported EDWCs. The conclusions or representation of the repor ted EDWCs in this assessment may change if the unidentified residues are of potential toxi cological concern (previously identified or not).

In addition, in several of the studies includi ng aerobic soil metabolism [and aerobic soil dissipation (seed treatment studi es)], there is an increasingl y large amount of unextracted residues. Additional data is needed to confirm th at the solvent used in the studies provides an

### 31 exhaustive extraction method. This includes confirma tion that the solvent system is sufficient to extract soil aged sedaxane residues as well as its transformation pr oducts. This data is needed for confirmation; however, it is not ex pected to have a substantial im pact on the results reported in this assessment. The only impact this is likely to have on this assessm ent is that additional transformation products may have been considered of potential toxicological concern. Inclusion of the unextracted residues in the total toxic residues would increase the model input value for the aerobic soil metabolism; however, a longer ha lf-life value would only result in a minimal increase in the EDWCs. This is because the sensi tivity of the models used in this assessment to aerobic soil metabolism half-life values >100 days is small.

Spray drift was not considered in the model r uns (assumed granular like application) since sedaxane is expected to be dried to the surface of the seed coat when planted. Spray drift is not expected to be a route of sedaxane dissi pation for the proposed seed treatment uses.

Incorporation of treated seeds was not consider ed. For surface water th e EDWCs could be lower as a result of incorporation; however, sin ce EDWCs for surface water are less than those estimated for groundwater. Consideration of in corporation will not have an effect on the groundwater EDWCs; therefore, no imp act on this DWA is expected.

### 32 APPENDIX A SEDAXANE KINETIC ANALYSIS

Aerobic Soil Metabolism of Sedaxane (MRID 47473448)

### 33

### 34

### 35 APPENDIX B GROUNDWATER ANALYSIS PRZM-GW Output

Potato “sedaxane only”

### 36 APPENDIX D SURFACE WATER ANALYSIS

Potato “Total Toxic Sedaxane Residues”

RUN No. 5 FOR Sedaxane ON Potato * INPUT VALUES *

------------- --------------------------------------------- ---------- RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

------------- --------------------------------------------- ---------- 0.080( 0.080) 1 1 481.0 14.0 GRANUL( 0.0) 91.0 0.0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

------------- --------------------------------------------- ---------- METABOLIC DAYS UNTIL HYDROLY SIS PHOTOLYSIS METABOLIC COMBINED (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

------------- --------------------------------------------- ---------- 1298.00 2 N/A 54.00- 6696.00 944.00 827.36

UNTREATED WATER CONC (MICR OGRAMS/LITER (PPB)) Ver 1.1.1 MAR 26, 2008

------------- --------------------------------------------- ---------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) CONCENTRATION CONCENTRATION

------------- --------------------------------------------- ---------- 4.095 1.203