### 1 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION **UNITED ST AT**  **ES ENVIRONMENT AL** **PROTECTION A GENCY** 

WASHINGTON, D.C. 20460



### PC Code: 128847 DP Barcode: 398836 **Date:** February 23 , 2012
**MEMORANDUM SUBJECT:**  Revised drinking water exposure assessment of parent difenoconazole and its

major metabolite , CGA

- 205375 (M1) for grape . **TO:** Sidney Jackson, Risk Manager Reviewer Barbara Madden, Risk Manager Registration Division (7505 P) **FROM:** Faruque Khan, Ph.D., Senior Fate Scientist

Environmental Risk Branch I Environmental Fate and Effects Division (7507P) **APPROVED BY**  **:** Nancy

Andrews , Ph.D., Branch Chief, Sujatha Sankula, Ph.D. Lead Biologist Environmental Risk Branch I Environmental Fate and Effects Division (7507P) This memorandum provides a revised drinking water assessment based on a recent recommendation from the Health Effects Division’s Residues of Concern Knowledgebase Sub

committee (ROCKS). The ROCKS recommended to include parent difenoconazole and its major metabolite , CGA

-205375 (M1) for drinking water assessment to establish tolerances for difenoconazole in support of human health risk assessment (US EPA, 2011 a, D391350)

. Previous ly recommended Estimated Drinking Water Concentrations (EDWCs) were based on aerial application of difenoconazole (parent only) for grape scenario (USEPA 2009, D361398). This drinking water assessment was performed using total residue method (i.e. parent plus CGA 205375) for grape following the approach used in a recent drinking water assessment for various crops (US EPA 2011 b , DP395784). The EDWCs values for acute (peak) , annual mean (chronic) and the highest 30 ye ar annual average (cancer chronic) concentrations were **17. 4**  μg/L , **11.8** μg/L, and **8.6** μg/L respectively

. Since the revised EDWCs for surface water are higher than the

### 2

previously

recommended EDWCs for this chemical, the current EDWCs for surface water supersede the EDWCs previously recommended for this chemical. Estimated ground water concentration of 1.12x 10 -2 

### μg/L for grape is lower than the previously

recommended concentration of 1.30x 10 -2 

### μg/Lf or citrus (US EPA, 2011 b ; D395784). Therefore, recommended EDWC for ground water is 1.30x 10 -2 

### μg/Land this concentration can be considered as both the acute and chronic values.

. **Drinking Water Exposure Modeling** The EDWCs were generated using EFED’s standard suite of models. S ince there is no modification of input parameters for PRZM/EXAMS and SCIGROW model s , detailed description of models and inputs parameters can be obtained from the previous assessment (USEPA, 2011 b , D395784). However, inputs for PRZM/EXAMS in **Table A** **- 1**  and for SCIGROW in **Table A -** **2** as well as outputs of PRZM/EXAMS and SCIGROW models for grape scenario were provided in the **Appendix A.** Standard percent cropped areas (PCA) were used for grape as estimates of the extent of watershed on which crops is grown (Effland et al. , 1999). The default agricultural PCA of 0.87 was used for the proposed uses because they are not confined to specific regions of the U.S

### 3 **References** Effland, W. R., N. C. Thurman, I. Kennedy. 1999. Proposed Methods for Determining Watershed

- derived Percent Crop Areas and Considerations for Applying Crop Area Adjustments to Surface Water Screening Models. Presentation to the FIFRA Science Advisory Panel, May 27, 1999. Online at: http://www.epa.gov/scipoly /sap/1999/index.htm US EPA, 2009 a . Difenoconazole (Parent Only) Drinking Water Assessment in Support of New Use Registration Action for Bulb Vegetables, Brassica (Cole) Leafy Vegetables, Cucurbit Vegetables, Citrus Fruit, Grapes, and Tree Nuts. May 28, 2009. (D361398) USEPA. 2009b . Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides , Version 2.1 . U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division, October 22, 2009

. USEPA. 2010 . Water Models. U.S. Environmental Protection Agency, Pesticides: Scienc e and Policy

. Online at: http://www.epa.gov/oppefed1/models/water/ US EPA, 2011 a . Difenoconazole **:** Report of the Residues of Concern Knowledgebase Sub

committee (ROCKS) . DP Code: D391350. US EPA, 20 11b

. Revised drinking water exposure assessment to establish a tolerance of parent difenoconazole and its major CGA

-205375 (M1) metabolite on fruiting vegetables group 8

- 10, low growing berry

subgroup, 13

- 07G except cranberry, citrus fruit group 10

- 10, pome fruit group, (subgroup 11) , and tuberous and corm vegetable (subgroup 1C). December 2 0 , 20 11

. (D 39 5784)

### 4 **APPENDIX A** 
**The input parameters used for PRZM/EXAMS modeling. Table**  **A -**  **1 . PRZM/EXAMS Chemical Specific Input Parameters for**  **Difenoconazole Parameter**  **Input Value and Unit Source** **/Comments** Maximum application rate Grape : 0. 46 lbs ai/A Product Inspire TM (EPA Reg. No.) 100

- 1262 Maximum number of applications 4 Product Label as above Method of application (CAM = 2) Foliar spray

-Aerial Product Label as above Application date NY Gape: August 18 Application date was assumed 7

- 14 days before harvest based on crop profile and label instructions: Minimum interval between applications 10 days Product Label as above Application efficiency 0.95 (aerial Application) EFED Model Input Guidance, Version 2.1 (200 9b ) a Spray drift 0.16 (Aerial Application) EFED Model Input Guidance, Version 2.1 (200 9b ) Partition coefficient Kocb 5381 mL/g MRID s: 42245135 and 469501 21 Henry’s Law constant 8.9 x 10 - 12 atm x m3 /mol MRID 46 515901 Hydrolysis Stable MRID 42245127 Aerobic soil metabolism (t 1/2) c 489.6 days MRID s.: 4695010 9

- 12 and 469501 14 Aerobic aquatic metabolism (t 1/2) d 632.9 days MRIDs.: 469501 16 & 469501 17 Anaerobic aquatic metabolism (t 1/2) e 1485.3 days MRID 4 69501 19 Aquatic photolysis t 1/2 (days) Stable MRID 46950105 Vapor pressure 2.5 x 10 - 10 mm Hg (25 oC) MRID 46 515901 Solubility in water 15 mg/L (25 oC) MRID 46515901 Molecular Weight 406.27 MRID 46950104 Percent cropped area 0.87 U.S. EPA 2003
a Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides (Version 2.1; Oct. 22, 2009b ) b There was a positive correlation between the KF values v s . organic matter content; therefore, the average Koc was used as an parameter. c The 90% of the upper confidence limit (UCL) of the mean metabolism half

- life

. d The 90% of the UCL of the mean metabolism half

- life of all available half

- lives but those obtained for high test rate. e At proposed application rate only one half

- life was available, the half

- life was multiplied by three (i.e., 3 x 495.1 days).

### 5

**An example (PA Tomato STD) input**  **and output of PRZM/EXAMS**  **modeling .**  stored as NYgrapeA.out Chemical: Difenconazole PRZM environment: NYGrapesSTD.txt mo dified Tueday, 29 May 2007 at 12:59:44 EXAMS environment: ir298.exv mo dified Tueday, 26 August 2008 at 05:14:08 Metfile: w14860.dvf mo dified Tueday, 26 August 2008 at 05:15:12 Water segment concentrations (ppb) Year Peak 96 hr 21 Day 60 Day 90 Day Yearly 1961 1.7 1.7 1.4 1.2 1.2 0.5 1962 9.8 9.1 7.3 5.7 5.4 2.7 1963 6.3 6.2 5.7 5.1 4.9 4.4 1964 10.3 9.8 8.9 7.5 7.0 5.5 1965 8.8 8.6 7.9 7.4 7.3 6.4 1966 11.7 11.2 10.1 8.8 8.4 7.3 1967 10.6 10.2 9.3 8.9 8.9 8.0 1968 9.2 9.0 8.7 8.4 8.2 7.8 1969 8.6 8.4 8.1 7.9 7.7 7.5 1970 13.5 13.0 12.2 10.7 10.2 8.1 1971 10.3 10.1 9.6 9.4 9.3 8.7 1972 10.0 9.9 9.4 9.1 9.0 8.6 1973 12 .5 12.0 10.8 9.7 9.3 8.5 1974 13.0 12.5 11.1 10.0 9.6 8.6 1975 19.4 18.8 16.3 13.7 12.9 10.0 1976 11.9 11.6 11.3 11.0 10.9 10.5 1977 18.2 17.5 16.4 15.3 14.6 11.4 1978 16.4 16.0 14.9 14.2 13.9 12.4 1979 19.5 18.9 17.2 16.4 15.8 13.2 1980 20.6 20.0 18.3 17. 0 16.5 14.3 1981 16.8 16.5 15.7 14.9 14.8 14.1 1982 15.7 15.4 14.7 14.2 14.0 13.3 1983 16.4 16.1 15.8 14.9 14.8 13.0 1984 18.9 18.2 16.4 14.7 14.2 12.9 1985 16.5 16.0 14.9 13.9 13.3 12.4 1986 20.0 19.2 17.5 15.3 14.6 12.6 1987 19.9 19.3 17.7 16.1 15.7 13.4 1988 17.0 16.6 15.7 14.9 14.8 13.6 1989 16.9 16.5 15.1 14.4 14.1 13.2 1990 21.3 20.5 18.9 16.7 16.1 13.4 Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly 0.0 21.3 20.5 18.9 17.0 16.5 14.3 0.1 20.6 20.0 18.3 16.7 16.1 14.1 0.1 20.0 19.3 17.7 16.4 15.8 13.6 0.1 19.9 19.2 17.5 16.1 15.7 13.4 0.2 19.5 18.9 17.2 15.3 14.8 13.4 0.2 19.4 18.8 16.4 15.3 14.8 13.3 0.2 18.9 18.2 16.4 14.9 14.8 13.2 0.3 18.2 17.5 16.3 14.9 14.6 13.2 0.3 17.0 16.6 15.8 14.9 14.6 13.0 0.3 16.9 16.5 15.7 14.7 14. 2 12.9 0.4 16.8 16.5 15.7 14.4 14.1 12.6 0.4 16.5 16.1 15.1 14.2 14.0 12.4

### 6

0.4 16.4 16.0 14.9 14.2 13.9 12.4 0.5 16.4 16.0 14.9 13.9 13.3 11.4 0.5 15.7 15.4 14.7 13.7 12.9 10.5 0.5 13.5 13.0 12.2 11.0 10.9 10.0 0.5 13.0 12.5 11.3 10.7 10.2 8.7 0.6 12.5 12. 0 11.1 10.0 9.6 8.6 0.6 11.9 11.6 10.8 9.7 9.3 8.6 0.6 11.7 11.2 10.1 9.4 9.3 8.5 0.7 10.6 10.2 9.6 9.1 9.0 8.1 0.7 10.3 10.1 9.4 8.9 8.9 8.0 0.7 10.3 9.9 9.3 8.8 8.4 7.8 0.8 10.0 9.8 8.9 8.4 8.2 7.5 0.8 9.8 9.1 8.7 7.9 7.7 7.3 0.8 9.2 9.0 8.1 7.5 7.3 6.4 0.9 8.8 8.6 7.9 7.4 7.0 5.5 0.9 8.6 8.4 7.3 5.7 5.4 4.4 0.9 6.3 6.2 5.7 5.1 4.9 2.7 1.0 1.7 1.7 1.4 1.2 1.2 0.5 0.1 20.0 19.3 17.6 16.3 15.8 13.6 Average of yearly averages: 9.9 Inputs generated by pe5.pl

- Novemeber 2006 Data used for this run: Output File: NYgrapeA Metfile: w14860.dvf PRZM scenario: NYGrapesSTD.txt EXAMS environment file: ir298.exv Chemical Name: Difenconazole Description Variable Name Value Units Comments Molecular weight mwt 406.27 g/mol Henry's Law Const. henry 8.90E

- 12 atm
-m^3/mol Vapor Pressure vapr 2.50E

- 10 torr Solubility sol 15 mg/L Kd Kd mg/L Koc Koc 5381 mg/L Photolysis half

- life kdp 0 days Half

- life Aerobic Aquatic Metabolism kbacw 632.9 days Halfife Anaerobic Aquatic Metabolism kbacs 1485.3 days Halfife Aerobic Soil Metabolism asm 489.6 days Halfife Hydrolysis: pH 7 0 days Half

- life Method: CAM 2 integer See PRZM manual Incorporation Depth: DEPI cm Application Rate: TAPP 0.128 kg/ha Application Efficiency: APPEFF 0.95 fraction Spray Drift DRFT 0.16 fraction of application rate applied to pond Application Date Date 18

- 07 dd/mm or dd/mmm or dd

-mm or dd

-mmm Interval 1 interval 10 days Set to 0 or delete line for single app. app. rate 1 apprate kg/ha Interval 2 interval 10 days Set to 0 or delete line for single app. app. rate 2 apprate kg/ha Interval 3 interval 10 days Set to 0 or delete line for single app. app. rate 3 apprate kg/ha Record 17: FILTRA IPSCND 1

### 7 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR Reservoir Flag for runoff calc. RUNOFF total none, monthly or total(average of entire run) 

### PCA Adjusted EDWCS

Peak 96 hr 21 Day 60 Day 90 Day Yearly Average of yearly averages 20.0 19.3 17.6 16.3 15.8 13.6 9.9 PCA Adjusted (0.87) **17.4** 16.8 15.4 14.2 13.7 **11.8 8.6**  

### The input parameters used for SCI**- GROW modeling**  **. Table**  **A -** **2. SCI -**  **GROW Input Parameters for Difenoconazole Applied on Multiple**  **Crops at the Maximum Label Application Rate.**  **Model Input Variable**  **Input Values** Koc (the lowest value of all available Koc s, MRIDs: 42245135 and 46950121 ) 1 3471 ml/g Application Rate 0. 114 lb. a.i./acre Number of Applications 4 Aerobic Soil Metabolism half

- life 2 223.6 days Hydrolysis Stable 1 The Koc shows greater than three

- folds variation, thus, the lowest value was uses per guidance as of Oct . 22 , 200 9 (USEPA 2009b)

. 2 Median of seven values. 

### I**nput and output of**  **SCIGROW modeling**  **.** 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:Difenconazole time is 9/20/2010 10:27:23

-------- ---------------------------------------------------------------- Application Number of Total Use Koc Soil Aerobic rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

---------------------------------------------- --------------------------

0.114 4.0 0.456 3.47E+03 185.0

------------------------------------------------------------------------

groundwater screening cond (ppb) = 1.12E
- 02 ************************************************************************