Document ID: EPA-HQ-OPP-2010-0122-0012
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-03-09T05:00Z

SEQ CHAPTER \h \r 1 U. S. ENVIRONMENTAL PROTECTION AGENCY

Washington, D.C. 20460	

									                          

	

OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES	

PC Code: 123802

DP Code: 373599, 373601

March 2, 2010

MEMORANDUM

SUBJECT:     Drinking Water Assessment for Fomesafen Use on Pepper

TO:	Michael Walsh

Joanne Miller, PM 23

Registration Division (7505P)           

                       

FROM:	James Lin, Environmental Engineer

	Environmental Risk Branch I

		Environmental Fate and Effects Division (7507P)

                        

APPROVED  Anita Pease, Acting Branch Chief

BY:	Environmental Risk Branch I

	Environmental Fate and Effects Division (7507P)

Summary

This assessment provides estimated drinking water concentrations (EDWC)
of the herbicide fomesafen in surface water and in ground water in
support of the human health risk assessment for assessing of new use on
pepper (DP373599, 373601).  This drinking water exposure memo addresses
the human exposure of fomesafen through ingestion of drinking water from
the new proposed use.  Based on the modeling analysis, the 1- in-10 year
fomesafen concentration in surface-source drinking water is not expected
to exceed 25.53 μg/L for peak (acute) and 2.87 μg/L for annual average
(non-cancer chronic) exposures.  The 30-year annual average
concentration is not expected to exceed 1.20 μg/L (cancer chronic). 
Therefore, the current EDWCs will not supersede the recommended drinking
water values previously performed for this chemical (DP 322213), and the
previous drinking water values should be used.

Estimated Drinking Water Concentrations (DP 322213)

Food uses of fomesafen considered in the previous assessment are cotton
and soybeans. Environmental fate data indicate fomesafen is very mobile
and highly persistent in terrestrial and aquatic environments.  Major
routes of dissipation from the application site are expected to be
runoff and leaching.  These data suggest fomesafen occurrence in surface
water and groundwater should be anticipated.  The 1- in-10 year
fomesafen concentration in surface-source drinking water is not expected
to exceed 34.8 μg/L for peak and 13.1 μg/L for annual average
exposures.  The 30-year annual average concentration is not expected to
exceed 6.5 μg/L.  Although SCI-GROW modeling predicts a fomesafen
concentration in ground water of 11.2 μg/L, a prospective ground water
monitoring study for soybeans on a vulnerable North Carolina site
reported maximum concentrations of fomesafen in ground water of 1 μg/L.
 EFED recommends using the ground water monitoring concentration of 1
μg/L as the benchmark concentration for fomesafen in ground water
source drinking water because it represents actual use conditions of
fomesafen on soybeans on a vulnerable soil.    

Label Use Information

Based on the proposed Reflex ® Herbicide label (EPA Reg. No. 100-993),
application rates and intervals for the new use of fomesafen on pepper
vary based on geographical regions as shown as Table 1. 

Table 1  Label Application Rates and Intervals for Fomesafen Use on
Pepper1

Region	States in Region	App Rate (lbs/A)	Application Interval

1	AL, AR, FL, GA, LA, MS, MO2, NC, OK2, SC, TN, TX2	0.375	1 year

2	DC, DE, IL2, IN2, KY, MD, OH2, PA3, WV, VA, 	0.375	2 year

3	CT, IA, ME, MA, MI3, NH, NJ, NY, PA3, RI, WI, VT	0.313	2 year

4	KS2, MI3, MN2, ND3, NE2 SD3, WI2	0.25	2 year

5	ND3, MN3, SD3	0.1875	2 year

1REFLEX 2.5 Gallon( (EPA Reg. No. 100-993)

2Does not include entire state

3Portions of state are in multiple regions

Among the five regions, region 1 allows the highest application amount
as it has a higher rate and a shorter application interval.  The use on
pepper is specified as a preplant non-incorporated pre-emergence
broadcast application.

Environmental Fate Summary

Major routes of fomesafen dissipation are leaching, runoff, and
microbial degradation.  Because fomesafen is persistent and mobile in
soil, it is expected to move from the application site into groundwater
and surface water.  Additionally, off-site movement of fomesafen is
expected through spray drift from aerial and ground spray.  The high
persistence of fomesafen is expected to contribute to year-to-year
accumulation in terrestrial and aquatic environments. 

Fomesafen is stable to abiotic hydrolysis.  It undergoes slow
photodegradation in water

(t1/2= 49 to 289 days).  Fomesafen is persistent (t1/2=9 to 99 weeks) in
aerobic soil and aquatic environments.  However, it degrades rapidly
(t1/2< 20 days) in anaerobic environments.  The major degradation
product of fomesafen is
5-(2-chloro-(,(,(-trifluoro-p-tolyloxy)-N-methylsulphonyl-panthranilamid
e (fomesafen amine).  A minor degradation product is
5-(2-chloro-(,(,(-trifluoro-p-tolyloxy) anthranilic acid (fomesafen
amino acid).   Neither degradate has been identified as a toxicological
concern. 

Fomesafen is expected to be very mobile in soil.  Simple partitioning
coefficients range from 0.51 in loamy coarse sand to 2.45 in sandy clay
loam soil.  Regression analysis indicates fomesafen sorption is not
dependent on soil organic matter content.  Aged soil column leaching
studies indicate degradation products of fomesafen are not mobile in
soils; less than 0.06% of applied radioactivity was detected in the
leachate samples.

Field dissipation studies in NC, IL, MS, AR, AL, TX, LA, SD, MN, KY, IA
and MO indicate fomesafen is moderately persistent to persistent (t1/2=
50 to 150 days ) in surface soils under actual use conditions. 
Fomesafen was detected at depths up to 30 inches in the soil profile. 
Fomesafen amine was the only degradation product identified in field
dissipation studies.  Prospective ground water monitoring in NC
indicates fomesafen moved through the soil profile into medium and deep
ground water.  

Fomesafen has a low potential for bioaccumulation in fish tissues. 
Bioaccumulation factors for fomesafen were 0.7 for whole fish, 0.2 for
edible tissues, and 5.2 for nonedible tissue.  Bioaccumulated residues
were depurated during a 14-day depuration period.  

Surface Water Assessment

The new proposed pepper use of fomesafen was modeled in the Florida
scenario in PRZM/EXAMS using index reservoir (IR) scenarios with the
default percent crop area (PCA) adjustment factor.  The estimated
drinking water concentrations in surface water were derived from Tier II
PRZM (Pesticide Root Zone Model; Version 3.12.2, May 12, 2005) and EXAMS
(Exposure Analysis Modeling System; Version 2.98.04.06, Apr. 25, 2005). 
PRZM simulates pesticide transport as a result of runoff, erosion, and
off-target spray drift from an agricultural field.  EXAMS estimates
environmental fate and transport of pesticides in surface water. 
Additionally, a graphical interface shell, PE5.pl (dated 7/27/2007), was
employed to facilitate the input of use-specific information in the PRZM
input and the EXAMS chemical files (Table 2).  

Linked crop-specific scenario and meteorological data were used to
estimate exposure as a result of fomesafen use on pepper. Simulations
were done using the index reservoir in EXAMS, which is a surrogate for a
permanent surface water drinking water environment.  Weather and
agricultural practices were simulated over 30 years to estimate the
1-in-10 year exceedance probability at the site.  

Table 2.  Input Parameters for PRZM-EXAMS Modeling of Fomesafen on
Pepper.

Parameter	

Value	

Reference

	Selected Physical/Chemical Properties

Molecular Weight (g/mol)	

420	

EPA 2020220

Water Solubility (mg/L)	

1200 (pH 7, 20oC)	

MRID 45048207

Vapor pressure (25(C)	

<7.5 x10-7 mmHg (50oC)	

HSDB

Henry's Law Constant	

7.5 x 10-13 atm m3/mol (estimated)	

HSDB

	Persistence

Hydrolysis t1/2 @	pH 7

	

stable	

Acc No. 071059

Photolysis t1/2 in Water	

289 days in pH 7 buffer solution	

MRID 40451101

Soil metabolism	

Aerobic t1/2

24-25(C (days)	

loamy sand (Frensham) 187. 6 and 630

sandy loam/loam (18 acres) 57 and 693

Calcareous silty clay loam (Gore) 349.3 and 527.1 

silty clay loam (Wisborough green) 207

upper 90th percentile of mean= 428.8 days

mean=387.84 days and SD=242.90 days 	

Acc No.  071059 and 00135660

Aquatic metabolism  Aerobic t1/2 (days)	

loamy sand (Frensham)  139.3 

sandy loam/loam (18 acres)  60.9

Calcareous silty clay loam (Gore)  92.4  

silty clay loam (Wisborough green) 115.5  

upper 90th percentile of mean= 115.71 days

mean=102.02 days and SD=33.44 days	

Acc No. 72158

Aquatic metabolism  Anaerobic t1/2	

Silt loam soil from Illinois half-life in the total system:	4.0 days

Loam soil from Mississippi half-life in the total system:	3.6 days 

Sand soil from North Carolina half-life in the total system:	5.1 days 

upper 90th percentile of mean= 5.08 days

mean= 4.233 days and SD= 0.777 days	

MRID 47865308

	Mobility/Adsorption-Desorption

Mobility - Adsorption/Desorption Aged

(Guideline 163-1)	

Blount silt loam-0.68.   This value represents  the lowest non-sand Kd. 
The Koc partition model was not used because there was no correlation
between  SOC and Kf . 	

Acc No 259413

Application Parameters

Application Efficiency	Aerial (0.95);  Ground (0.99)	Input Guidance
Document

Spray Drift Amount	Aerial (0.15); Ground (0.064)

	

The application rate used is the recommended maximum label application
rate. The standard scenarios were developed by EFED to represent
nationwide crop coverage and high-end vulnerability sites to runoff and
erosion and, therefore, pesticide transport. The application information
used in the PRZM/EXAMS modeling is provided in Table 3. 

Table 3.  Standard EFED modeling scenario for fomesafen pepper use

PRZM 

Crop 

Scenario	Application Date

dd-mm	Maximum Single Application

Rate (lb ai/A)

Pepper

Florida Pepper	20-08	0.375 / year

The modeling results of estimated drinking water concentrations (EDWC)
are listed in Tables 4 (before PCA adjustment) and 5 (after PCA
adjustment).  The default PCA value of 0.87 is adjusted for pepper use. 
The complete PE5 outputs are included in the Appendix. 

Table 4.  Estimated Drinking Water Concentrations before Percent Crop
Area (PCA) Adjustment 

PRZM 

Crop 

(unit: μg/L; ppb)

Florida Pepper: aerial	29.349	3.294	1.376

Florida Pepper: ground	29.253	3.257	1.259

Table 5.  Estimated Drinking Water Concentrations after Percent Crop
Area (PCA) Adjustment 

PRZM 

Crop 

Scenario	1 in 10 year annual peak concentration (acute) 	1 in 10 year
annual mean concentration (non-cancer chronic)	30 year annual mean
concentration (cancer chronic).  

Pepper                                                          (unit:
μg/L; ppb)

Florida Pepper: aerial	25.534	2.866	1.197

Florida Pepper: ground	25.450	2.834	1.095

The aerial application has the higher estimated drinking water
concentrations.  The 1 in 10 year annual peak concentration of 25.53
µg/L should be used to assess acute concerns; the 1 in 10 year annual
mean concentration of 2.87 µg/L should be used for non-cancer chronic
assessment; and the 30 year annual mean concentration of 1.20 µg/L
should be used for assessing cancer chronic concerns. 



Appendix 

stored as frflpdwa.out

Chemical: Fomesafen

PRZM environment: FLpeppersSTD.txt	modified Thuday, 24 May 2007 at
09:44:22

EXAMS environment: ir298.exv	modified Tueday, 26 August 2008 at 05:14:08

Metfile: w12844.dvf	modified Tueday, 26 August 2008 at 05:14:22

Water segment concentrations (ppb)

Year	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

1961	6.432	6.115	4.997	3.413	2.653	0.7136

1962	5.081	4.832	3.954	2.807	2.204	0.6318

1963	9.879	9.391	7.947	5.392	4.171	1.154

1964	29.92	28.45	23.31	15.58	12.06	3.325

1965	2.658	2.527	2.06	1.383	1.069	0.4647

1966	14.91	14.19	12.38	8.472	6.569	1.787

1967	2.639	2.514	2.16	1.513	1.177	0.4084

1968	7.881	7.602	6.291	4.719	3.734	1.029

1969	6.786	6.458	5.457	3.819	2.988	0.8661

1970	13.64	12.97	10.58	7.066	5.467	1.516

1971	7.031	6.824	5.768	3.987	3.125	0.9179

1972	5.502	5.285	4.378	2.942	2.267	0.6455

1973	3.152	3.004	2.813	2.005	1.559	0.4464

1974	5.754	5.482	4.548	3.126	2.435	0.6757

1975	4.053	3.865	3.432	2.365	1.833	0.5246

1976	3.421	3.258	2.926	2.313	1.836	0.5224

1977	7.529	7.16	6.392	4.376	3.41	0.9471

1978	3.662	3.509	2.916	2.239	1.79	0.535

1979	6.78	6.452	5.369	3.644	2.962	0.8417

1980	39.62	37.68	31.34	21.05	16.25	4.405

1981	24.21	23.02	19.72	13.37	10.33	3.016

1982	3.988	3.793	3.122	2.147	1.66	0.5832

1983	4.413	4.194	3.529	2.462	1.919	0.5384

1984	18.6	17.9	15.49	10.56	8.175	2.219

1985	7.165	6.874	5.716	3.884	3.058	0.9352

1986	5.706	5.425	4.619	3.314	2.575	0.7341

1987	3.081	2.962	2.496	2.077	1.655	0.483

1988	81.19	77.2	62.89	41.6	31.98	8.55

1989	8.825	8.388	7.167	4.949	3.833	1.411

1990	3.137	2.982	2.622	1.954	1.526	0.4598

Sorted results

Prob.	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

0.032258064516129	81.19	77.2	62.89	41.6	31.98	8.55

0.0645161290322581	39.62	37.68	31.34	21.05	16.25	4.405

0.0967741935483871	29.92	28.45	23.31	15.58	12.06	3.325

0.129032258064516	24.21	23.02	19.72	13.37	10.33	3.016

0.161290322580645	18.6	17.9	15.49	10.56	8.175	2.219

0.193548387096774	14.91	14.19	12.38	8.472	6.569	1.787

0.225806451612903	13.64	12.97	10.58	7.066	5.467	1.516

0.258064516129032	9.879	9.391	7.947	5.392	4.171	1.411

0.290322580645161	8.825	8.388	7.167	4.949	3.833	1.154

0.32258064516129	7.881	7.602	6.392	4.719	3.734	1.029

0.354838709677419	7.529	7.16	6.291	4.376	3.41	0.9471

0.387096774193548	7.165	6.874	5.768	3.987	3.125	0.9352

0.419354838709677	7.031	6.824	5.716	3.884	3.058	0.9179

0.451612903225806	6.786	6.458	5.457	3.819	2.988	0.8661

0.483870967741936	6.78	6.452	5.369	3.644	2.962	0.8417

0.516129032258065	6.432	6.115	4.997	3.413	2.653	0.7341

0.548387096774194	5.754	5.482	4.619	3.314	2.575	0.7136

0.580645161290323	5.706	5.425	4.548	3.126	2.435	0.6757

0.612903225806452	5.502	5.285	4.378	2.942	2.267	0.6455

0.645161290322581	5.081	4.832	3.954	2.807	2.204	0.6318

0.67741935483871	4.413	4.194	3.529	2.462	1.919	0.5832

0.709677419354839	4.053	3.865	3.432	2.365	1.836	0.5384

0.741935483870968	3.988	3.793	3.122	2.313	1.833	0.535

0.774193548387097	3.662	3.509	2.926	2.239	1.79	0.5246

0.806451612903226	3.421	3.258	2.916	2.147	1.66	0.5224

0.838709677419355	3.152	3.004	2.813	2.077	1.655	0.483

0.870967741935484	3.137	2.982	2.622	2.005	1.559	0.4647

0.903225806451613	3.081	2.962	2.496	1.954	1.526	0.4598

0.935483870967742	2.658	2.527	2.16	1.513	1.177	0.4464

0.967741935483871	2.639	2.514	2.06	1.383	1.069	0.4084

0.1	29.349	27.907	22.951	15.359	11.887	3.2941

					Average of yearly averages:	1.37622

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: frflpdwa

Metfile:	w12844.dvf

PRZM scenario:	FLpeppersSTD.txt

EXAMS environment file:	ir298.exv

Chemical Name:	Fomesafen

Description	Variable Name	Value	Units	Comments

Molecular weight	mwt	420	g/mol

Henry's Law Const.	henry	7.5e-13	atm-m^3/mol

Vapor Pressure	vapr	7.5e-7	torr

Solubility	sol	1200	mg/L

Kd	Kd	0.68	mg/L

Koc	Koc		mg/L

Photolysis half-life	kdp	289	days	Half-life

Aerobic Aquatic Metabolism	kbacw	115.71	days	Halfife

Anaerobic Aquatic Metabolism	kbacs	5.08	days	Halfife

Aerobic Soil Metabolism	asm	428.8	days	Halfife

Hydrolysis:	pH 7	0	days	Half-life

Method:	CAM	1	integer	See PRZM manual

Incorporation Depth:	DEPI	0	cm

Application Rate:	TAPP	0.42	kg/ha

Application Efficiency:	APPEFF	0.95	fraction

Spray Drift	DRFT	0.16	fraction of application rate applied to pond

Application Date	Date	20-08	dd/mm or dd/mmm or dd-mm or dd-mmm

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)

stored as frflpdwg.out

Chemical: Fomesafen

PRZM environment: FLpeppersSTD.txt	modified Thuday, 24 May 2007 at
09:44:22

EXAMS environment: ir298.exv	modified Tueday, 26 August 2008 at 05:14:08

Metfile: w12844.dvf	modified Tueday, 26 August 2008 at 05:14:22

Water segment concentrations (ppb)

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4.199	4.048	3.374	2.261	1.744	0.5008

0.645161290322581	4.01	3.813	3.113	2.123	1.671	0.4831

0.67741935483871	3.214	3.054	2.577	1.755	1.375	0.4327

0.709677419354839	2.764	2.631	2.352	1.648	1.28	0.3859

0.741935483870968	2.716	2.584	2.196	1.59	1.279	0.3806

0.774193548387097	2.659	2.529	2.093	1.516	1.235	0.3702

0.806451612903226	2.507	2.388	2.034	1.425	1.105	0.3665

0.838709677419355	2.196	2.122	1.808	1.359	1.104	0.3299

0.870967741935484	2.09	1.994	1.74	1.275	0.9979	0.3092

0.903225806451613	1.906	1.812	1.543	1.227	0.969	0.3057

0.935483870967742	1.465	1.402	1.173	0.812	0.6343	0.2902

0.967741935483871	1.214	1.155	1.024	0.7555	0.5924	0.2473

0.1	29.253	27.814	22.879	15.318	11.833	3.2577

					Average of yearly averages:	1.25894333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: frflpdwg

Metfile:	w12844.dvf

PRZM scenario:	FLpeppersSTD.txt

EXAMS environment file:	ir298.exv

Chemical Name:	Fomesafen

Description	Variable Name	Value	Units	Comments

Molecular weight	mwt	420	g/mol

Henry's Law Const.	henry	7.5e-13	atm-m^3/mol

Vapor Pressure	vapr	7.5e-7	torr

Solubility	sol	1200	mg/L

Kd	Kd	0.68	mg/L

Koc	Koc		mg/L

Photolysis half-life	kdp	289	days	Half-life

Aerobic Aquatic Metabolism	kbacw	115.71	days	Halfife

Anaerobic Aquatic Metabolism	kbacs	5.08	days	Halfife

Aerobic Soil Metabolism	asm	428.8	days	Halfife

Hydrolysis:	pH 7	0	days	Half-life

Method:	CAM	1	integer	See PRZM manual

Incorporation Depth:	DEPI	0	cm

Application Rate:	TAPP	0.42	kg/ha

Application Efficiency:	APPEFF	0.99	fraction

Spray Drift	DRFT	0.064	fraction of application rate applied to pond

Application Date	Date	20-08	dd/mm or dd/mmm or dd-mm or dd-mmm

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)

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