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

	PC Code:  100249
	DP Barcode:  428982
	June 1, 2016

MEMORANDUM

SUBJECT:	Penflufen Drinking Water Assessment for Proposed New Uses on:  bulb onion subgroup 3-07A; green onion subgroup 3-07B; and sugar beet seed treatment associated with products EverGol Prime (EPA Reg. No. 264-1119) and EverGol Energy (EPA Reg. No. 264-1122)

FROM:	Ibrahim Abdel-Saheb, Ph.D, Environmental Scientist
		Environmental Risk Branch VI
      Environmental Fate and Effects Division (7507P) 
      
THRU:	Mark Corbin, Branch Chief
		William P. Eckel, Ph.D., Senior Science Advisor
		Monica Wait, RAPL		
      Environmental Risk Branch VI
      Environmental Fate and Effects Division (7507P)

TO:		Christina Swartz, Branch Chief
		Janet Cowins, Risk Assessor
		Risk Assessment Branch 2
      Health Effects Division (7509P)
       
      Tony Kish, Product Manager Team 22 
      Shaunta Hill, Risk Manager Reviewer
      Fungicide Branch 
      Registration Division (7505 P)
      
      Nancy Keller, Risk Manager Reviewer
      Barbara Madden, Team Leader
      Minor Use and Emergency Response Branch
      Registration Division (7505P)
      
      
This memorandum provides estimates of human drinking water exposure to the fungicide penflufen, (BYF 14182; N-[2-(1,3-dimethylbutyl)phenyl]-5fluoro-1,3-dimethyl-1H-pyrazole-4-carboxamide; CAS#: 494793-67-8; PC code: 100249). Penflufen is a succinate dehydrogenase inhibitor (SDHI) in the pyrazole carboxamide family. It is proposed for use as a fungicide seed treatment for protection against certain soilborne, seedborne, and post-emergence diseases of crops.  Penflufen is currently registered for use on a wide variety of agricultural crop sites.  The proposed registration is for use on bulb onion subgroup 3-07A, green onion subgroup 3-07B, and sugar beets as a seed treatment

The penflufen end-use products associated with the proposed new uses are:  EverGol Prime (EPA Reg. No. 264-1119), and EverGol Energy (EPA Reg. No. 264-1122.  The proposed penflufen application rate on a per acre basis, 0.001-0.06 pounds of active ingredient per acre (lb a.i./A), is lower than the rate which was previously assessed (0.28 lb a.i./A).

Note that this assessment incorporates new models which have been implemented since the previous drinking water assessment was conducted, and therefore a comparison of estimated drinking water concentrations (EDWCs) are shown in Table 1 below.  With the Surface Water Concentration Calculator (SWCC) the graphical user interface (GUI) has replace the PE5 GUI which includes updates to both PRZM and EXAMS. The previous ground water model, SCI-GROW, has been replaced by PRZM-GW.  

The Health Effects Division's (HED) Residues of Concern Knowledgebase Subcommittee (ROCKS) reported that two major transformation products [BYF 14182-3-hydroxybutyl (pen3HB) and BYF 14182-3-pyrazolyl-AAP (AAP)] should be included in the drinking water exposure assessment since they may be of toxicological concern (i.e., they are assumed to be of equal toxicity to the parent in the
absence of toxicological data).  For that reason, EDWCs) were calculated for penflufen plus two degradates assumed to be equally toxic to the parent (BYF 14182-3-hydroxybutyl (pen3HB) and BYF 14182-3-pyrazolyl-AAP (AAP)).  Model outputs are included in Appendix I. 

EFED recommends that HED use the estimated drinking water concentrations for the previously registered potato use which are shaded in Table 1 below, for use in the human health risk assessment.  EDWCs for the potato use were recalculated using the new PRZM-GW model and are higher than EDWCs calculated for the proposed new uses.
Because EDWCs from groundwater modeling (using the PRZM-GW model) are higher than those calculated for surface water (using the SWCC model), ground water is considered the driver for penflufen. As seen in Table 1, the groundwater was also the driver in the previous drinking water assessment.


Table 1. Estimated Drinking Water Concentrations (EDWCs) for Proposed New Uses and Previously Registered Uses of Penflufen.
                            Surface Water Modeling
                                   (FIRST)*
                        EDWCs Reported in Previous DWA
                            DP Barcode: 386698,2010
                                    (SWCC)
                 Provided as comparison of new and old models.
                                   (SWCC)**
                          EDWCs for Proposed New Uses

                                    Potato
                                       @
                                0.28 lb a.i./A
                            (Idaho potato scenario)
                                    Potato
                                       @
                                0.28 lb a.i./A
                            (Idaho potato scenario)
                                 green onions
                                       @
                                 0.062 a.i./A
                           (CA green onion scenario)
                                  bulb onions
                                       @
                                     a.i./A
                              (GA onion scenario)
                                  sugar beets
                                       @
                                     a.i./A
                         (MN sugar beet     scenario)
Acute (ppb)
                                     11.4
Peak (1-in-10 yr)
                                     5.09
                                     0.870
                                     1.310
                                     0.046
Chronic (ppb)

                                      6.2
365-day Avg (1-in-10 yr)
                                     3.95
                                     0.689
                                     0.273
                                     0.031

                                       
Entire Simulation Mean
                                     2.04
                                     0.304
                                     0.113
                                     0.017
                             Ground Water Modeling





Groundwater
EDWCs (ppb)
                                   SCI-GROW
                           Acute & Chronic (ppb)
                        EDWCs Reported in Previous DWA
                            DP Barcode: 386698,2010
                                    PRZM-GW
                 Provided as comparison of new and old models.
                             (NC coastal scenario)
                                    PRZM-GW
                          EDWCs for Proposed New Uses
                             (NC coastal scenario)

                                       
                                       
                                     16.6
Peak Concentration (ppb)
                                      123
                                     27.3
                                     4.49 
                                     0.428


Post-Breakthrough Mean Concentration (ppb)
                                     84.8
                                     19.7
                                     3.18
                                     0.295


Entire Simulation Mean Concentration (ppb)
                                     65.7
                                     15.5
                                     2.45
                                     0.229
*: Previous DWA used a PCA of 0.87.


For the previously registered use on potato at 0.28 lb a.i./A using the PRZM-GW model, the following available scenarios were modeled:  FL potato, FL citrus, GA coastal, and NC coastal, and WI sand.  
Although the FL potato scenario is more relevant for modeling potato; as well the fact that the state of FL has higher harvested area by acres compared to the other available groundwater scenarios (USDA NASS, 2015), EDWCs resulting from the NC coastal scenario are presented in Table 1 as this scenario yields the highest EDWCs. 


Similarly, using PRZM-GW, for the modeling of penflufen on proposed new use on onion, the following available scenarios were modeled: FL potato, FL citrus, GA coastal, and NC coastal, and WI sand. Although Georgia has higher acreage of onion produced (onions-usa.org), the NC coastal scenario resulted in highest EDWCs (shaded) and are presented in Table 1.

Physical, Chemical, Fate, and Transport Properties of Penflufen

Penflufen is persistent in aerobic and anaerobic conditions, and is moderately mobile based on the FAO soil mobility classifications (mean Koc = 365; MRID 48023546) (USEPA, 2006a). The compound is nonvolatile, lipophilic, and does not bioconcentrate in aquatic organisms. Penflufen is persistent in soil with half-lives ranging from 115 to 433 days in aerobic soil from two studies conducted in six soils (MRID 48023552, 48023553). The compound degrades very slowly in anaerobic soil, with an extrapolated half-life of 886 days (MRID 48023555). There is no evidence of degradation via hydrolysis, which was studied across environmentally relevant pHs (pH 5, 7, and 9 at 50°C; MRID 48023547). Penflufen also degrades slowly by aerobic aquatic metabolism, with half-lives ranging from 267 to 301 days (MRID 48023556). There is no evidence of degradation in anaerobic aquatic systems (MRID 48023557). A potentially major route of degradation may be aqueous photolysis (environmental half-life of 83 days; MRID 48023548); however photolysis is slow and only likely to play a significant role in shallow, clear waters.

Penflufen is expected to persist in both terrestrial and aquatic environments. The degradate Pen3HB is much more mobile than the parent, but the AAP degradate is comparatively immobile.  Under aerobic conditions, AAP can be slowly metabolized, but it is stable to anaerobic metabolism. AAP persists, with half-lives ranging from 116-260 days (there are no metabolism data for Pen-3HB). Penflufen was detected in submitted terrestrial field dissipation studies above the level of quantitation (LOQ) at depths up to 60 cm, however the majority of reported detections were from the upper soil layers (0-15 cm).

The two major degradates observed in laboratory and field studies are summarized in Table 2.  The table also shows the environmental fate studies in which these degradates were identified and the maximum formation in each study. HED reported in the Residues of Concern Knowledge Base Committee (ROCKS) that the parent penflufen, and the metabolites penflufen-hydroxybutyl (Pen-3HB) and penflufen-pyrazolyl-AAP (AAP) were identified as potential residues of concern in drinking water. Since the structures of the metabolites are similar to the parent, they are assumed to have similar toxicities (D387299, June 15, 2011).


Table 2. Table of Transformation Products Formed in Environmental Fate Studies.





Modeling

The Tier 1 (FIRST) was used in the 2010 drinking water assessment (DP Barcode 386698) and resulted in the following estimated drinking water concentrations (EDWCs) for surface water: 11.4 for acute, and 6.2 ppb chronic.  For groundwater, the model SCI-GROW gave acute and chronic EDWCs of 16.6 ppb.  Since the previous drinking water assessment was conducted in 2010, EFED has introduced new surface water and groundwater models [i.e., Surface Water Concentration Calculator (SWCC), and PRZM-GW, respectively]. 

This current assessment includes residues from both the parent, penflufen, and the metabolites
penflufen-hydroxybutyl (Pen-3HB) and penflufen-pyrazolyl-AAP (AAP), assumed to be equally toxic to the parent. The input parameters presented below are for total toxic residues (TTR).

Application rates were calculated based on the best available data for seeding rates for particular uses, (USDA, 2015; and EPA 2011).


Table 3. SWCC Input Parameter Values for Penflufen (Total Toxic Residues values presented, where appropriate).

                                Input Parameter
                                     Value
                                    Source
                                   Comments
Application Rate in lbs a.i./A 

Potato 
Green onions 
Bulb onions 
Sugar beets 
                                       
                                       
                                     0.280
                                     0.062
                                     0.010
                                     0.001
                                       
                                       
                             EPA Reg. No. 264-1122
                             EPA Reg. No. 264-1119
                             EPA Reg. No. 264-1119
                             EPA Reg. No. 264-1122
                                       

Molecular Mass (g/mol)
                                    317.41
Foot Print Pesticide Properties Database; parent data used as default for degradate@ http://sitem.herts.ac.uk/aeru/iupac/Reports/1655.htm

Spray Drift Fraction
                                       0
                                       
Seed treatment; no spray drift
Application efficiency


                                       1
Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 
Transport of Pesticides. 2009

Vapor Pressure (Torr)
                                    9.0E-9
                                 MRID 48023537

Solubility in Water at 20°C (mg/L)
                                     10.9
Foot Print Pesticide Properties Database; parent data used as default for degradate@ http://sitem.herts.ac.uk/aeru/iupac/Reports/1655.htm

Soil-Water Partition Coefficient (KFOC)
                                     47.8
                                 MRID 48023546
                                 MRID 48023544
                                 MRID 48023545
Sorption based on pen-3HB which has a lower sorption coefficient compared to the parent.
Aerobic Soil Metabolism Half-life (days)
                                     1513
                                 MRID 48023552
                                 MRID 48023553
TTR. 

Aerobic Aquatic Metabolism Half-life (days)
                                      978
                                 MRID 48023556
TTR
Anaerobic Aquatic Metabolism Half-life (days)
                                    Stable
                                       
                                       
                                 MRID 48023557
                          No evidence of degradation
Hydrolysis Half- life (days)
                                    stable
                                 MRID 48023547

Aqueous Photolysis -Half-life (days)
                                      83
                                 MRID 48023548



Table 4. PRZM-GW input parameters.

Input parameter
Value
Source
Comments
Soil-Water Partition Coefficient (KFOC)
40
MRID 47443206
Median of five values of degradate with highest
mobility
Aerobic Soil Metabolism  Half-life (days)
642
MRID 47443210-13

Median of six TTR half-lives 
Hydrolysis Half-life (days)
stable
MRID 48023547



Monitoring Data for Penflufen

No monitoring data are available for penflufen; the USGS NAWQA database was searched (http://waterqualitydata.us/portal/).


References

 Crop Production 2014 Summary. 2015. USDA. National Agricultural Statistics Service @
      http://www.usda.gov/nass/PUBS/TODAYRPT/cropan15.pdf. Accessed February 10, 2016.
      
 Acres Planted per Day and Seeding Rates of crops grown in the United States. 2011. Office of Chemical Safety and pollution Prevention. Biological and Economic Analysis.

                                  Appendix I
                                       
                                  SWCC Model

CA onion

Table 1. Estimated Environmental Concentrations (ppb) for penflufen.
Peak (1-in-10 yr)
0.870
4-day Avg (1-in-10 yr)
0.867
21-day Avg (1-in-10 yr)
0.856
60-day Avg (1-in-10 yr)
0.833
365-day Avg (1-in-10 yr)
0.689
Entire Simulation Mean
0.304

Table 2. Summary of Model Inputs for penflufen.
Scenario
CAonion_WirrigSTD
Cropped Area Fraction
1.0
Koc (ml/g)
47.8
Water Half-Life (days) @ 25 °C
978
Benthic Half-Life (days) @ 25 °C
0
Photolysis Half-Life (days) @ 40 °Lat
83
Hydrolysis Half-Life (days)
0
Soil Half-Life (days) @ 22 °C
1513
Foliar Half-Life (days)
35
Molecular Wt
317.41
Vapor Pressure (torr)
9E-9
Solubility (mg/l)
10.9

Table 3. Application Schedule for penflufen.
Date (Mon/Day)
Type
Amount (kg/ha)
Eff.
Drift
1/6
Incorporated to 1.27 cm
0.07
1
0




GA onion

Table 1. Estimated Environmental Concentrations (ppb) for penflufen.
Peak (1-in-10 yr)
1.31
4-day Avg (1-in-10 yr)
1.28
21-day Avg (1-in-10 yr)
1.15
60-day Avg (1-in-10 yr)
1.01
365-day Avg (1-in-10 yr)
0.273
Entire Simulation Mean
0.113

Table 2. Summary of Model Inputs for penflufen.
Scenario
GAOnion_WirrigSTD
Cropped Area Fraction
1.0
Koc (ml/g)
47.8
Water Half-Life (days) @ 25 °C
978
Benthic Half-Life (days) @ 25 °C
0
Photolysis Half-Life (days) @ 40 °Lat
83
Hydrolysis Half-Life (days)
0
Soil Half-Life (days) @ 22 °C
1513
Foliar Half-Life (days)
35
Molecular Wt
317.41
Vapor Pressure (torr)
9E-9
Solubility (mg/l)
10.9

Table 3. Application Schedule for penflufen.
Date (Mon/Day)
Type
Amount (kg/ha)
Eff.
Drift
9/5
Incorporated to 1.27 cm
0.0112
1
0


MN sugar beet

Table 1. Estimated Environmental Concentrations (ppb) for penflufen.
Peak (1-in-10 yr)
0.460E-01
4-day Avg (1-in-10 yr)
0.457E-01
21-day Avg (1-in-10 yr)
0.451E-01
60-day Avg (1-in-10 yr)
0.429E-01
365-day Avg (1-in-10 yr)
0.313E-01
Entire Simulation Mean
0.168E-01

Table 2. Summary of Model Inputs for penflufen.
Scenario
MNsugarbeetSTD
Cropped Area Fraction
1.0
Koc (ml/g)
47.8
Water Half-Life (days) @ 25 °C
978
Benthic Half-Life (days) @ 25 °C
0
Photolysis Half-Life (days) @ 40 °Lat
83
Hydrolysis Half-Life (days)
0
Soil Half-Life (days) @ 22 °C
1513
Foliar Half-Life (days)
35
Molecular Wt
317.41
Vapor Pressure (torr)
9E-9
Solubility (mg/l)
10.9

Table 3. Application Schedule for penflufen.
Date (Mon/Day)
Type
Amount (kg/ha)
Eff.
Drift
5/6
Incorporated to 1.27 cm
0.00112
1
0

ID Potato

Table 1. Estimated Environmental Concentrations (ppb) for penflufen.
Peak (1-in-10 yr)
5.09
4-day Avg (1-in-10 yr)
5.06
21-day Avg (1-in-10 yr)
5.02
60-day Avg (1-in-10 yr)
5.25
365-day Avg (1-in-10 yr)
3.95
Entire Simulation Mean
2.04

Table 2. Summary of Model Inputs for penflufen.
Scenario
IDNpotato_WirrigSTD
Cropped Area Fraction
1.0
Koc (ml/g)
47.8
Water Half-Life (days) @ 25 °C
978
Benthic Half-Life (days) @ 25 °C
0
Photolysis Half-Life (days) @ 40 °Lat
83
Hydrolysis Half-Life (days)
0
Soil Half-Life (days) @ 22 °C
1513
Foliar Half-Life (days)
35
Molecular Wt
317.41
Vapor Pressure (torr)
9E-9
Solubility (mg/l)
10.9

Table 3. Application Schedule for penflufen.
Date (Mon/Day)
Type
Amount (kg/ha)
Eff.
Drift
5/21
Incorporated to 5.08 cm
0.314
0.99
0.135




                                    PRZM-GW
      Post breakthrough averages to be used as chronic and cancer EDWCs.
                                     Crop 
                                  Scenario *
                                       
                               Peak Conc. (ppb)
                      Post-Breakthrough Mean Conc. (ppb)
                      Entire Simulation Mean Conc. (ppb)
Potato
                              Delmarva sweet corn
                                     91.3
                                     68.3
                                     56.0

                                  FL potato 
                                      49
                                      40
                                      35

                       Florida Citrus - FL Central Ridge
                                     82.3
                                      67
                                     61.0

                          GA - Southern Coastal Plain
                                     36.3
                                     29.2
                                     25.1

                           NC Eastern Coastal Plain
                                      123
                                     84.8
                                     65.7








Table 1. Groundwater Results for Penflufen and the NC Eastern Coastal Plain - Norfolk loamy sand - Cotton Scenario.
Peak Concentration (ppb)
     123
Post-Breakthrough Mean Concentration (ppb)
    84.8
Entire Simulation Mean Concentration (ppb)
    65.7
Average Breakthrough Time (days)
2322.608
Throughputs
4.718833

Table 2. Chemical Properties for Groundwater Modeling of Penflufen.
Koc (ml/g)
40
Surface Soil Half Life (days)
642
Hydrolysis Half Life (days)
0
Diffusion Coefficent Air (cm2/day)
0.0
Henry's Constant
0.0
Enthalpy (kcal/mol)
0.0

Table 3. Pesticide application scheme used for Penflufen.  This application scheme was applied every year of the simulation.
Application Date
(Month/Day)
Application Method
Application Rate
(kg/ha)
5/21
Ground application with mass distribution increasing proportionally with depth to 4 cm
0.314











Green onion

Table 1. Groundwater Results for Penflufen and the NC Eastern Coastal Plain - Norfolk loamy sand - Cotton Scenario.
Peak Concentration (ppb)
    27.3
Post-Breakthrough Mean Concentration (ppb)
    19.7
Entire Simulation Mean Concentration (ppb)
    15.5
Average Breakthrough Time (days)
2322.608
Throughputs
4.718833

Table 2. Chemical Properties for Groundwater Modeling of Penflufen.
Koc (ml/g)
40
Surface Soil Half Life (days)
642
Hydrolysis Half Life (days)
0
Diffusion Coefficint Air (cm2/day)
0.0
Henry's Constant
0.0
Enthalpy (kcal/mol)
0.0

Table 3. Pesticide application scheme used for Penflufen.  This application scheme was applied every year of the simulation.
Application Date
(Month/Day)
Application Method
Application Rate
(kg/ha)
1/6
Ground application with mass distribution increasing proportionally with depth to 4 cm
0.07

