 Page 1 of 6 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D. C. 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES February 16, 2006 MEMORANDUM SUBJECT: Aquatic Exposure Assessment for the Use of the Fungicide of 2( Thiocyanomethylthio) benzothiazole ( TCMTB) as a Seed Treatment on Cotton, Wheat, Barley, Oats, Rice, Sugar Beets, and Safflower PC Code: 035603 DP Barcode: 324012 FROM: James Lin, Environmental Engineer Environmental Risk Branch 1 Environmental Fate and Effects Division ( 7507C)

TO: Kathryn Jakob, Chemical Review Manager Regulatory Management Branch II Antimicrobials Division ( 7510C)

Kathryn Montague, Senior Biologist Risk Assessment and Science Support Branch Antimicrobials Division ( 7510C)

THRU: Nader Elkassabany, Acting Branch Chief Environmental Risk Branch 1 Environmental Fate and Effects Division ( 7507C)

This aquatic exposure assessment provides the estimated environmental concentrations ( EEC) for the use of 2( Thiocyanomethylthio) benzothiazole ( TCMTB) as a seed treatment on cotton, wheat, barley, oats, rice, sugar beets, and safflower. For this action, EFED considered risk only from parent compound of TCMTB and not any degradates associated with TCMTB. Page 2 of 6 Label Information The following labels have been provided to EFED as the basis for this aquatic exposure assessment.

COTGARD ® and ORYZETMcontain three active ingredients, Carboxin ( 14.35%), TCMTB ( 5.00%) and Metalaxyl ( 2.40%). The targeted uses are for cottonseed and rice seed.

NU FLOW ND contains Chloroneb ( 23.5%) and TCMTB ( 9.0%). The only use is for cottonseed treatment.

NUSAN ® 30 E. C. contains TCMTB ( 30%). The label seed treatment uses include: cotton, wheat, barley, oats, rice, sugar beets, and safflower.

ARGENTTM 30 contains TCMTB ( 30%). The only use is for cottonseed treatment.

The first two labels were not addressed, since TCMTB is a minor active ingredient. For this aquatic exposure assessment, the last two labels will be based, since TCMTB is the sole active ingredient. According to the two labels, the application rates for various seed treatments are tabulated below.

Crop Application Rate ( fl oz/ 100 lbs) Max. Seeding Rate ( lbs/ ac) Rate ( lbs ai/ ac)

Cotton 5 18 0.018 Safflower 2 100 0.041 Sugar beets 2 8 0.003 Rice 1.25 150 0.039 Wheat 1.25 150 0.039 Oats 1.25 128 0.033 Barley 1.25 100 0.026 The maximum seeding rate information is based on EFED's T REX model, except for rice use and wheat use, which are according to HED SOPs. The application rate ranges from 0.003 lb ai/ ac to 0.041 lb ai/ ac.

Modeling Approach For this aquatic exposure assessment, the highest rate of 0.041 lb ai/ ac is used for the screening purpose. We used the tier 1 models: GENEEC ( version 2.0; Aug. 1, 2001) and SCI GROW Page 3 of 6 ( version 2.3; Nov. 4, 2003) screening models to assess estimated concentrations of TCMTB in surface water and ground water, respectively. These models and their descriptions are available at the EPA internet site:

http:// www. epa. gov/ oppefed1/ models/ water/ .

Conclusions: For surface water exposures, results from GENEEC indicate that the TCMTB concentrations of 0.28 ppb ( ug/ L), 0.26 ppb, 0.20 ppb, 0.12 ppb, and 0.08 ppb, respectively, for peak, 4 day average, 21 day average, 60 day average, and 90 day average exposure. For ground water, SCI GROW indicates that TCMTB concentrations are not likely to exceed 0.00014 : g/ L. Full model inputs and outputs are in Appendix 1.

Since our models are not specifically designed to estimate concentrations for pesticides used for seed treatment, there are uncertainties in their predictive potential. However, these uncertainties are not expected to substantially decrease the conservativeness of the Tier 1 modeling results.

Uncertainties in the Modeling Several factors suggests low environmental exposure from seed treatment, including ( 1) seed treatment pesticides are applied at low rates; ( 2) adjuvants are used to encourage pesticide binding to the seed coat; ( 3) physicochemical properties of seed treatment pesticides generally exhibit low mobility to retain the pesticide near the seed coat and root zone; ( 4) seeds are normally incorporated, which is expected to limit environmental exposure; and ( 5) seed treatments may have indoor use patterns ( e. g., seed storage). In addition to these factors, the main uncertainty in our assessment for the use of TCMTB as a seed treatment is that we have not accounted for the potential for sorption to, or reaction on, the seed coat. Because of model limitations and because we have no data to the contrary, we assumed that TCMTB does not sorb to the seed coat, but only to the soil. In effect, this assumption provides conservative runoff and leaching scenarios.

SCI GROW was developed using Koc values ranging from 32   180 ml/ g and half lives from 13   1000 days. The input values for TCMTB are outside these ranges; therefore, the extrapolation increases the uncertainty of the ground water estimated concentrations.

Input Parameter Selection Based on environmental fate data, TCMTB is expected to be relatively immobile and persistent in terrestrial environments. Freundlich sorption coefficients ( Kf), exponent values ( 1/ n) for concentration in water, and Freundlich coefficients normalized for organic carbon ( Koc) are in Table 1 below ( MRID 426314 01). The aerobic soil metabolism half life for TCMTB was 1.4 days ( MRID 435322 01). TCMTB had a photodegradation half life of 1.5 hours under ideal the laboratory exposure conditions ( MRID 426309 01). Page 4 of 6 Table 1: Freundlich Soil Sorption Coefficients for TCMTB*

Soil Kf 1/ n Koc Sand 0.99 0.93 765 Sandy loam 9.9 0.86 2120 Silt loam 62.7 0.76 7896 Clay 22.1 0.85 2554 Clay loam 3.5 0.96 282 * Concentration units in soil are g/ g soil; in water, g/ mL water For purposes of this aquatic exposure assessment, the GENEEC and SCI GROW model input parameters selected for TCMTB are shown in Tables 2 and 3 below ( see Appendix 1 for full model inputs and outputs).

Table 2: GENEEC Input Parameters for TCMTB SOURCE VALUE*

Application rates Label ( Reg. 2935 389) 0.041 lb/ acre Aerobic soil metabolism half life MRID 433522 01 4.2 days ( 3 x 1.4 days)

Koc ( lowest non sand soil Freundlich sorption coefficient ) MRID 426314 01 282 ( soil mass in grams, volume of water in mL)

Solubility Product Chemistry 45 ppm Photodegradation in water half life MRID 426309 01 0.188 days ( 3 x 1.5 hr)

Number of Applications Label ( Reg. 2935 389) 1 Application Type Model Option Granular ( 4 inch)

Aerobic Aquatic Metabolism Half life MRID 425086 01 20.7 days ( 3 x 6.9 days)

* Values based on EFED input parameter selection policy and processes. Page 5 of 6 Table 3: SCI GROW Input Parameters for TCMTB SOURCE VALUE*

Application rate Label ( Reg. 2935 389) 0.041 lb/ acre Aerobic soil met. half life MRID 433522 01 4.2 days ( 3 x 1.4 days)

Koc ( Freundlich organic matter sorption coefficient, lowest value) MRID 426314 01 282 ( soil mass in grams, volume of water in mL)

Number of applications Label ( Reg. 2935 389) 1 * Values based on EFED input parameter selection policy and processes. Page 6 of 6 APPENDIX 1 SCI GROW and GENEEC Model Input and Output Tables SCI GROW version 2.3, November 4, 2003 SCIGROW VERSION 2.3 ENVIRONMENTAL FATE AND EFFECTS DIVISION OFFICE OF PESTICIDE PROGRAMS U. S. ENVIRONMENTAL PROTECTION AGENCY SCREENING MODEL FOR AQUATIC PESTICIDE EXPOSURE SciGrow version 2.3 chemical: TCMTB time is 1/ 31/ 2006 13: 40: 47  Application Number of Total Use Koc Soil Aerobic rate ( lb/ acre) applications ( lb/ acre/ yr) ( ml/ g) metabolism ( days)  0.041 1.0 0.041 2.82E+ 02 4.2  groundwater screening cond ( ppb) = 1.38E 04 ************************************************************************

GENEEC version 2.0, August 1, 2001 RUN No. 1 FOR TCMTB ON Safflower * INPUT VALUES *  RATE (#/ AC) No. APPS & SOIL SOLUBIL APPL TYPE NO SPRAY INCORP ONE( MULT) INTERVAL Koc ( PPM ) (% DRIFT) ( FT) ( IN)  .041( .041) 1 1 282.0 45.0 GRANUL( .0) .0 4.0 FIELD AND STANDARD POND HALFLIFE VALUES ( DAYS)  METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED ( FIELD) RAIN/ RUNOFF ( POND) ( POND EFF) ( POND) ( POND)  4.20 2 N/ A .19 23.31 20.70 10.96 GENERIC EECs ( IN NANOGRAMS/ LITER ( PPTr)) Version 2.0 Aug 1, 2001  PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC  277.81 263.46 198.64 116.11 84.13