              OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION
                 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460







                                                                PC Code: 128847
                                                             Decision #: 447590
                                                             DP Barcode: 395784
                                                                               
                                                        Date: December 20, 2011
                                                                               
                                                                               
                                                                    MEMORANDUM	

SUBJECT:	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).  

TO:	Sidney Jackson, Risk Manager Reviewer
               Barbara Madden, Risk Manager
	Registration Division (7505P)	
	
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 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 CGA-205375 (M1) metabolite for drinking water assessment to establish tolerances for difenoconazole in support of human health risk assessment (US EPA, 2011, D391350). This revised drinking water assessment was performed using total residue method (i.e. parent plus CGA 205375) on the requested crops, 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). 
      
      Difenoconazole can be applied as a foliar spray through ground or aerial application on various crops according to the Inspire[(TM)] (EPA Reg. No. 100-1262) label. Table 1 below provides information of previous actions related to drinking water assessments. Revised drinking water assessment was performed only for the scenarios with highest EDWCs for crops listed in Table 1. Table 2 provides information related to modeled scenarios for this assessment. The modeling approach for surface water and ground water are consistent with the earlier approach except the half-life values for biotic degradation in the environment. The percent of CGA-205375 formation during biotic metabolism in soil and aquatic environments was included into half-life calculations (Appendix A) and used in the revised modeling. Since abiotic (i.e. hydrolysis and aquatic photolysis) degradation of difenoconazole is stable, no further half-life estimation is required. The EDWCs are also based on the maximum proposed application rates ranging from 0.33 to 0.5 lbs/A for aerial application specified in the product label. 
      The EDWCs for the human health risk assessment are presented in Table 2. For surface water, the EDWCs for the crops modeled in this assessment did not exceed the EDWCs for grape reported in the previous drinking water assessment (U.S. EPA 2009a; D361398). The Estimated Drinking Water Concentrations (EDWCs) for grape scenario provided the highest exposure in surface water (U.S. EPA 2009; D361398). The reported values for acute, annual mean (chronic) concentration and the highest 30 year annual average concentrations were 15.8 ug/L, 10.4 ug/L, and 7.62 ug/L respectively. Therefore, the current EDWCs for surface water do not supersede the drinking water concentrations previously estimated for this chemical.
      Estimated ground water concentration of 1.30x 10[-2] ug/L for citrus is higher than the previously recommended concentration of 1.28x 10[-2] ug/L for ornamentals (US EPA, 2007; D333319). Therefore, recommended EDWCs for ground water is 1.30x 10[-2] ug/L and this concentration can be considered as both the acute and chronic values. 

Table 1. List of previous actions for drinking water assessment
DP Barcodes
                                     Date
                              Title of Assessment
333319 and
340041
June 19, 2007
Amended Difenoconazole (Parent Only) Drinking Water Assessment in Support of New Use Registration Action for Fruiting Vegetables[1], Tuberous, Corn[1], Vegetables Subgroup, Pome Fruit, Ornamentals, and Sugar beets.	
361398

May 28, 2009
Difenoconazole (Parent Only) Drinking Water Assessment in
Support of New Use Registration Action for Bulb Vegetables,
Brassica (Cole) Leafy Vegetables, Cucurbit Vegetables, Citrus
Fruit[1], Grapes, and Tree Nuts.
375778 and 380513
                                                                Dec 16, 2010   

Drinking Water Exposure Assessment to Establish a Tolerance of
parent difenoconazole on carrot, chickpeas, soybean, stone fruits,
and strawberry[1].  
1 Scenarios with higher EDWCs were modeled in this revised assessment

Table 2. Estimated Drinking Water Concentrations (EDWCs) in Surface Water and Ground Water Resulting from Applications of Difenoconazole
Drinking Water Source (model)
                                      Use
                                   Scenario 
                                (modeled rate)
                          1-in-10 year acute (ug/L)
                         1-in-10 year chronic (ug/L)
                           30- year average (ug/L)
Surface Water[1] (PRZM/EXAMS)
Fruiting Vegetables:
PA Tomato STD
FL Pepper STD
(0.46 lbs ai/acre)

                                     10.31
                                     8.36
                                       
                                     6.02
                                     2.85
                                       
                                     4.52
                                     2.19

Citrus:
FL Citrus STD
(0.5lbs ai/acre)
                                       
                                     8.01
                                       
                                     3.30
                                       
                                     2.63

Low growing berry  
FL Strawberry STD
 (0.46 lbs ai/acre)
                                       
                                     9.89
                                       
                                       
                                     3.56
                                       
                                       
                                     2.97
                                       

Pome Fruits:
PA Apple STD
(0.33 lbs ai/acre)
                                       
                                     7.08
                                       
                                     3.99
                                       
                                     3.01

Tuberous and corm vegetables
ME Potato STD
 (0.46lbs ai/acre)
                                       
                                       
                                     10.25
      
      
      6.62
                                       
                                       
                                     5.38
Groundwater 
(SCI-GROW)
 For Citrus  crops
(4 app. X 0.125 lbs ai/acre)
                                       
                                 1.30 x 10[-2]
                                       
                                 1.30 x 10[-2]
                                       
                                 1.30x 10[-2]
Bold text denotes maximum estimated EDWC values for this assessment.  All values were adjusted with PCA factor of 0.87.

The modeling results of various scenarios for EDWCs are listed in Appendix B. Standard percent cropped areas (PCA) were used for all uses 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.  Since there is no modification of input parameters for PRZM/EXAMS and SCI-GROW models except biotic degradation half-life parameters, detailed description of models can be obtained from the previous assessment for grapes (U.S.EPA, 2009a, D361398). Inputs for PRZM/EXAMS in Table B-1 and for SCIGROW in Table B-2 as well as examples output of PRZM/EXAMS and SCIGROW models were provided in the Appendix B. Tables B-3 provides pre-PCA and post-PCA adjusted EDWCs for difenoconazole.

Monitoring Data

      Difenconazole is not included as one of the analytes monitored in U.S. surface and groundwater under the USGS's National Water Quality Assessment (NAWQA) program.  
 Drinking Water Exposure Modeling

      Estimated drinking water concentrations (EDWCs) were generated using EFED's standard suite of models.  The proposed uses from the provided label were assessed. 

Models

	Pesticide Root Zone Model (PRZM v3.12.2, May 12, 2005) and Exposure Analysis Modeling System (EXAMS v2.98.04.06, April 25, 2005) are simulation models coupled with the input PE5.pl shell (PE5, PE Version 5.0, November 15, 2006) to generate EDWCs of difenoconazole residues that may occur in surface water used as drinking water.  The PRZM model simulates pesticide movement and transformation on and across the agricultural field resulting from crop applications.  The EXAMS model simulates pesticide loading via runoff, erosion, and spray drift assuming a standard watershed of 172.8 ha that drains into an adjacent standard drinking water index reservoir of 5.26 ha, an average depth of 2.74 m.  A more detailed description of the index reservoir watershed can be found in Jones et al., 1998.  The coupled PRZM/EXAMS model and users manuals may be downloaded from the U.S. Environmental Protection Agency (EPA) Water Models web-page (U.S. EPA, 2010).  Percent Crop Areas (PCA) that account for the maximum area within a watershed that may be planted with the modeled crop are applied to concentrations predicted by PRZM/EXAMS.

	Screening Concentration in Ground Water (SCI-GROW v2.3, Jul. 29, 2003) is a regression model used as a screening tool to estimate pesticide concentrations found in ground water used as drinking water.  SCI-GROW was developed by fitting a linear model to ground water concentrations with the Relative Index of Leaching Potential (RILP) as the independent variable.  Ground water concentrations were taken from 90-day average high concentrations from Prospective Ground Water studies.  The RILP is a function of aerobic soil metabolism and the soil-water partition coefficient.  The output of SCI-GROW represents the concentrations of residues that might be expected in shallow unconfined aquifers under sandy soils, which is representative of the ground water most vulnerable to pesticide contamination and likely to serve as a drinking water source.  The SCI-GROW user's manual is currently under development; however, information concerning the model can be found on the EPA Water Models web-page (USEPA, 2010).  

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

Jones, R. D., S. Abel, W. R. Effland, R. Matzner, R. Parker.  1998.  An Index Reservoir for Use in Assessing Drinking Water Exposure.  Proposed Methods for Basin-scale Estimation of Pesticide Concentrations in Flowing Water and Reservoirs for Tolerance Reassessment.  Presentation to FIFRA Science Advisory Panel, June 29-30, 1998.  Online at: http://www.epa.gov/scipoly/sap/1998/index.htm

USEPA.  2007.  Amended Difenoconazole (Parent Only) Drinking Water Assessment in Support of New Use Registration Action for Fruiting Vegetables, Tuberous, Corn, Vegetables Subgroup, Pome Fruit, Ornamentals, and Sugar beets. U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects Division, DWA Memorandum, June 19, 2007. (D333319 and D340041)

US EPA, 2009a.  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: Science and Policy.  Online at: http://www.epa.gov/oppefed1/models/water/

US EPA, 2011. Difenoconazole:  Report of the Residues of Concern Knowledgebase Sub-committee (ROCKS). DP Code: D391350.  

                                  APPENDIX A
                                       
                     Total Residue Half-life Calculation 
Aerobic Soil Metabolism



















Table B-1. Estimated half-lives in aerobic soil
MRID # 
                               Half-life (days)
46950109
                                     126.0
46950110
                                     113.6
46950111
                                     216.6
46950111
                                     247.6
46950111
                                     223.6
46950112-46950113
                                     693.1
46950114-46950115
                                     770.2
Half-life (90[th] Percentile): 489.6


Aerobic Aquatic Metabolism (Total System)









Table B-2. Estimated half-lives in aerobic aquatic system
MRID # 
                               Half-life (days)
46950116
                                     495.1
46950116
                                     407.7
46950117 and 46950118
                                     630.1
Half-life (90[th] Percentile): 632.9


Anaerobic Aquatic Metabolism 





                                  APPENDIX B
                                       
                                       

The input parameters used for PRZM/EXAMS modeling.
      
Table B-1.  PRZM/EXAMS Chemical Specific Input Parameters for Difenoconazole
Parameter
Input Value and Unit
Source/Comments
Maximum application rate
Fruiting vegetable: 0.46 lbs ai/A 
Citurs: 0.5 lbs ai/A
Low growing berry: 0.46 lbs ai/A
Pome fruit: 0.33 ai/A
Tuberous & crom vegetable: 0.46 lbs 
Product Inspire[TM] 
(EPA Reg. No. 100-1262)
Maximum number of applications
4 (except Pome fruit)
5 pome fruit
Product Label as above
Method of application (CAM = 2)
Foliar spray -Aerial
Product Label as above
Minimum interval between applications 
7 days
Product Label as above
Application efficiency 
0.95 (aerial Application)
EFED Model Input Guidance, Version 2.1 (2009b) a
Spray drift
0.16 (Aerial Application)
EFED Model Input Guidance, Version 2.1 (2009b)
Partition coefficient Koc[b]
5381 mL/g
MRIDs: 42245135 and 46950121
Application date
PA Tomato: June 30
FL Pepper: November 15
FL Strawberry:  February 15
FL Citrus: June 08
PA Apple: June 30
ME Potato: June 20
Application dates were assumed 7-14 days before harvest based on crop profile and label instructions:  
Henry's Law constant
8.9 x 10-12  atm x m[3]/mol
MRID 46515901
Hydrolysis
Stable
MRID 42245127
Aerobic soil metabolism (t1/2)[c]
489.6 days
MRIDs.: 46950109-12 and 46950114
Aerobic aquatic metabolism (t1/2) d
632.9 days
MRIDs.: 46950116 & 46950117
Anaerobic aquatic metabolism (t1/2) [e]
1485.3 days
MRID 46950119
Aquatic photolysis t1/2 (days) f
Stable
MRID 46950105
Vapor pressure
2.5 x 10-10 mm Hg (25 [o]C)
MRID 46515901
Solubility in water 
15 mg/L (25 [o]C)
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 vs. organic matter content; therefore, the average Koc was used as an parameter.  
[c] The 90% of the 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).
[f] The maximum value available.





An example (PA Tomato STD) input and output of  PRZM/EXAMS modeling.


stored as PATomato.out
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Chemical: Difenoconazole
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
PRZM environment: PAtomatoSTD.txt
modified Tueday, 29 May 2007 at 13:01:58
                                                                               
                                                                               
                                                                               
EXAMS environment: ir298.exv
modified Tueday, 26 August 2008 at 05:14:08
                                                                               
                                                                               
                                                                               
Metfile: w14751.dvf
modified Tueday, 26 August 2008 at 05:15:00
                                                                               
                                                                               
                                                                               
Water segment concentrations (ppb)
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                     Year
                                     Peak
                                     96 hr
                                    21 Day
                                    60 Day
                                    90 Day
                                    Yearly
                                                                               
                                     1961
                                     4.28
                                     3.90
                                     3.16
                                     2.66
                                     2.37
                                     0.98
                                                                               
                                     1962
                                     4.35
                                     4.13
                                     3.51
                                     3.30
                                     3.23
                                     2.33
                                                                               
                                     1963
                                     5.04
                                     4.81
                                     4.28
                                     3.99
                                     3.64
                                     3.03
                                                                               
                                     1964
                                     5.45
                                     5.21
                                     4.87
                                     4.30
                                     4.18
                                     3.73
                                                                               
                                     1965
                                     5.24
                                     5.06
                                     4.75
                                     4.56
                                     4.37
                                     3.93
                                                                               
                                     1966
                                     10.76
                                     10.05
                                     8.10
                                     6.42
                                     6.02
                                     4.44
                                                                               
                                     1967
                                     8.90
                                     8.54
                                     7.57
                                     6.57
                                     6.21
                                     5.30
                                                                               
                                     1968
                                     10.27
                                     9.70
                                     8.09
                                     6.73
                                     6.42
                                     5.35
                                                                               
                                     1969
                                     16.70
                                     15.53
                                     13.14
                                     9.85
                                     8.89
                                     6.31
                                                                               
                                     1970
                                     8.30
                                     8.08
                                     7.78
                                     7.34
                                     6.99
                                     6.49
                                                                               
                                     1971
                                     11.91
                                     11.24
                                     9.44
                                     8.18
                                     7.62
                                     6.40
                                                                               
                                     1972
                                     10.28
                                     9.76
                                     8.80
                                     7.81
                                     7.45
                                     6.66
                                                                               
                                     1973
                                     11.34
                                     10.77
                                     9.19
                                     7.88
                                     7.50
                                     6.67
                                                                               
                                     1974
                                     9.85
                                     9.55
                                     8.70
                                     8.24
                                     7.89
                                     6.94
                                                                               
                                     1975
                                     16.48
                                     15.38
                                     12.43
                                     9.83
                                     9.04
                                     7.05
                                                                               
                                     1976
                                     10.46
                                     10.05
                                     9.10
                                     8.11
                                     7.83
                                     7.22
                                                                               
                                     1977
                                     7.58
                                     7.39
                                     7.08
                                     6.86
                                     6.81
                                     6.43
                                                                               
                                     1978
                                     7.40
                                     7.18
                                     6.99
                                     6.45
                                     6.18
                                     5.76
                                                                               
                                     1979
                                     7.57
                                     7.32
                                     6.83
                                     6.38
                                     6.11
                                     5.69
                                                                               
                                     1980
                                     7.24
                                     6.95
                                     6.18
                                     5.92
                                     5.47
                                     5.11
                                                                               
                                     1981
                                     7.57
                                     7.25
                                     6.77
                                     6.07
                                     5.77
                                     5.25
                                                                               
                                     1982
                                     6.27
                                     6.10
                                     5.91
                                     5.54
                                     5.44
                                     4.93
                                                                               
                                     1983
                                     7.18
                                     6.90
                                     6.21
                                     5.49
                                     5.22
                                     4.77
                                                                               
                                     1984
                                     6.34
                                     6.14
                                     5.87
                                     5.36
                                     5.17
                                     4.89
                                                                               
                                     1985
                                     6.16
                                     5.93
                                     5.30
                                     4.90
                                     4.88
                                     4.53
                                                                               
                                     1986
                                     8.58
                                     8.17
                                     7.09
                                     6.29
                                     5.87
                                     4.89
                                                                               
                                     1987
                                     8.12
                                     7.78
                                     7.01
                                     6.14
                                     6.00
                                     5.10
                                                                               
                                     1988
                                     8.28
                                     7.89
                                     6.82
                                     5.92
                                     5.64
                                     5.10
                                                                               
                                     1989
                                     7.56
                                     7.27
                                     6.78
                                     6.29
                                     6.04
                                     5.24
                                                                               
                                     1990
                                     7.75
                                     7.46
                                     6.63
                                     6.22
                                     6.02
                                     5.49
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Sorted results
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                     Prob.
                                     Peak
                                     96 hr
                                    21 Day
                                    60 Day
                                    90 Day
                                    Yearly
                                                                               
                                     0.03
                                     16.70
                                     15.53
                                     13.14
                                     9.85
                                     9.04
                                     7.22
                                                                               
                                     0.06
                                     16.48
                                     15.38
                                     12.43
                                     9.83
                                     8.89
                                     7.05
                                                                               
                                     0.10
                                     11.91
                                     11.24
                                     9.44
                                     8.24
                                     7.89
                                     6.94
                                                                               
                                     0.13
                                     11.34
                                     10.77
                                     9.19
                                     8.18
                                     7.83
                                     6.67
                                                                               
                                     0.16
                                     10.76
                                     10.05
                                     9.10
                                     8.11
                                     7.62
                                     6.66
                                                                               
                                     0.19
                                     10.46
                                     10.05
                                     8.80
                                     7.88
                                     7.50
                                     6.49
                                                                               
                                     0.23
                                     10.28
                                     9.76
                                     8.70
                                     7.81
                                     7.45
                                     6.43
                                                                               
                                     0.26
                                     10.27
                                     9.70
                                     8.10
                                     7.34
                                     6.99
                                     6.40
                                                                               
                                     0.29
                                     9.85
                                     9.55
                                     8.09
                                     6.86
                                     6.81
                                     6.31
                                                                               
                                     0.32
                                     8.90
                                     8.54
                                     7.78
                                     6.73
                                     6.42
                                     5.76
                                                                               
                                     0.35
                                     8.58
                                     8.17
                                     7.57
                                     6.57
                                     6.21
                                     5.69
                                                                               
                                     0.39
                                     8.30
                                     8.08
                                     7.09
                                     6.45
                                     6.18
                                     5.49
                                                                               
                                     0.42
                                     8.28
                                     7.89
                                     7.08
                                     6.42
                                     6.11
                                     5.35
                                                                               
                                     0.45
                                     8.12
                                     7.78
                                     7.01
                                     6.38
                                     6.04
                                     5.30
                                                                               
                                     0.48
                                     7.75
                                     7.46
                                     6.99
                                     6.29
                                     6.02
                                     5.25
                                                                               
                                     0.52
                                     7.58
                                     7.39
                                     6.83
                                     6.29
                                     6.02
                                     5.24
                                                                               
                                     0.55
                                     7.57
                                     7.32
                                     6.82
                                     6.22
                                     6.00
                                     5.11
                                                                               
                                     0.58
                                     7.57
                                     7.27
                                     6.78
                                     6.14
                                     5.87
                                     5.10
                                                                               
                                     0.61
                                     7.56
                                     7.25
                                     6.77
                                     6.07
                                     5.77
                                     5.10
                                                                               
                                     0.65
                                     7.40
                                     7.18
                                     6.63
                                     5.92
                                     5.64
                                     4.93
                                                                               
                                     0.68
                                     7.24
                                     6.95
                                     6.21
                                     5.92
                                     5.47
                                     4.89
                                                                               
                                     0.71
                                     7.18
                                     6.90
                                     6.18
                                     5.54
                                     5.44
                                     4.89
                                                                               
                                     0.74
                                     6.34
                                     6.14
                                     5.91
                                     5.49
                                     5.22
                                     4.77
                                                                               
                                     0.77
                                     6.27
                                     6.10
                                     5.87
                                     5.36
                                     5.17
                                     4.53
                                                                               
                                     0.81
                                     6.16
                                     5.93
                                     5.30
                                     4.90
                                     4.88
                                     4.44
                                                                               
                                     0.84
                                     5.45
                                     5.21
                                     4.87
                                     4.56
                                     4.37
                                     3.93
                                                                               
                                     0.87
                                     5.24
                                     5.06
                                     4.75
                                     4.30
                                     4.18
                                     3.73
                                                                               
                                     0.90
                                     5.04
                                     4.81
                                     4.28
                                     3.99
                                     3.64
                                     3.03
                                                                               
                                     0.94
                                     4.35
                                     4.13
                                     3.51
                                     3.30
                                     3.23
                                     2.33
                                                                               
                                     0.97
                                     4.28
                                     3.90
                                     3.16
                                     2.66
                                     2.37
                                     0.98
                                                                               
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                                                               
                                     0.10
                                     11.85
                                     11.19
                                     9.41
                                     8.23
                                     7.89
                                     6.91
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Average of yearly averages:
                                     5.20
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Inputs generated by pe5.pl - Novemeber 2006
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Data used for this run:
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Output File: PATomato
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Metfile:
w14751.dvf
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
PRZM scenario:
PAtomatoSTD.txt
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
EXAMS environment file:
ir298.exv
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Chemical Name:
Difenoconazole
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
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
30-06
dd/mm or dd/mmm or dd-mm or dd-mmm
                                                                               
Interval 1
interval
                                                                              7
days
Set to 0 or delete line for single app.
app. rate 1
apprate
                                                                               
kg/ha
                                                                               
                                                                               
                                                                               
                                                                               
Interval 2
interval
                                                                              7
days
Set to 0 or delete line for single app.
app. rate 2
apprate
                                                                               
kg/ha
                                                                               
                                                                               
                                                                               
                                                                               
Interval 3
interval
                                                                              7
days
Set to 0 or delete line for single app.
app. rate 3
apprate
                                                                               
kg/ha
                                                                               
                                                                               
                                                                               
                                                                               
Record 17:
FILTRA
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
IPSCND
                                                                              1
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
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)


The input parameters used for SCI-GROW modeling.

Table B-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 Kocs, MRIDs: 42245135 and 46950121)[1]
3471 ml/g
Application Rate
 0.125 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, 2009 (USEPA 2009b).
[2] Median of seven values.
                                       
                                       
                    Input 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:Difenoconazole
                         time is 12/19/2011   8:36:36
   ------------------------------------------------------------------------
      Application      Number of       Total Use    Koc      Soil Aerobic
    rate (lb/acre)  applications   (lb/acre/yr)  (ml/g)   metabolism (days)
   ------------------------------------------------------------------------
         0.125           4.0           0.500      3.47E+03      223.6
   ------------------------------------------------------------------------
                 groundwater screening cond (ppb) =   1.30E-02
   ************************************************************************

                                       
Table B-3 Estimated drinking water concentrations before and after percent crop area (PCA) adjustment 
                              Non-Adjusted EDWCs
Scenarios
Peak
96 hr
21 Day
60 Day
90 Day
Yearly Average
Annual Average
                                   PA Tomato
                                     11.85
                                     11.19
                                     9.41
                                     8.23
                                     7.89
                                     6.91
                                     5.20
                                   FL Pepper
                                     9.61
                                     8.62
                                     6.22
                                     4.74
                                     4.32
                                     3.28
                                     2.51
                                   FL Citrus
                                     9.21
                                     8.45
                                     7.10
                                     5.46
                                     5.01
                                     3.80
                                     3.02
                                 FL Strawberry
                                     11.37
                                     10.37
                                     7.81
                                     5.87
                                     5.38
                                     4.09
                                     3.42
                                   PA Apple
                                     8.13
                                     7.70
                                     6.53
                                     5.62
                                     5.40
                                     4.59
                                     3.46
                                   ME Potato
                                     11.78
                                     11.42
                                     10.22
                                     9.13
                                     8.72
                                     7.61
                                     6.18








                              PCA Adjusted EDWCs
Scenarios
Peak
96 hr
21 Day
60 Day
90 Day
Yearly Average
Annual Average
                                   PA Tomato
                                   10.31[1]
                                     9.74
                                     8.19
                                     7.16
                                     6.86
                                     6.02
                                     4.52
                                   FL Pepper
                                     8.36
                                     7.50
                                     5.41
                                     4.12
                                     3.76
                                     2.85
                                     2.19
                                   FL Citrus
                                     8.01
                                     7.35
                                     6.18
                                     4.75
                                     4.36
                                     3.30
                                     2.63
                                 FL Strawberry
                                     9.89
                                     9.02
                                     6.80
                                     5.11
                                     4.68
                                     3.56
                                     2.97
                                   PA Apple
                                     7.08
                                     6.70
                                     5.69
                                     4.89
                                     4.70
                                     3.99
                                     3.01
                                   ME Potato
                                     10.25
                                     9.93
                                     8.89
                                     7.95
                                     7.59
                                     6.62
                                     5.38
[1] Bolded values are the highest concentrations observed in modeled scenarios



