### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF CHEMICAL SAFETY

AND P OLLU T ION P REVENTION



### PC Code: 118602

DP Barcode: 402305

Date : August 16

, 201 2

MEMORANDUM

SUBJECT: Tier I Drinking Water Assessment for the Section 3 Proposed Registration of

Imazosulfuron on Melon Subgroup 9A and Tuberous and Corm Subgroup 1C

TO: Andrew Ertman

, Risk Manager Reviewer

Barbara Madden , Risk Manager

Herbicide Branch
Registration Division

FROM: Faruque Khan

, Ph.D., Senior Scientist

Environmental Risk Branch I

Environmental Fate and Effects Division

APPROVED

BY : Nancy Andrews

, Ph.D., Branch Chief
Sujatha Sankula, Ph.D.

, Lead Biologist

Environmental Risk Branch I

Environmental Fate and Effects Division

A Tier I screening

- level drinking water assessment was conducted to support the human health
risk assessment for the Section 3 proposed new use registration of imazosulfuron

. Modeled
application rates represent the maximum application rates o n the proposed label for use on the
melon subgroup 9A and the tuberous subgroup IC (EPA Reg. No. pending )

. F oliar ground spray application ( ground spray ) is proposed for new uses. Tier 1 surface water and groundwater
modeling was conducted for two ground spray applications with 45 days interval for the tuberous
and corm subgroup 1C at a rate of 0.15 lb a.i./A

. In addition, Tier 1 surface water modeling was

also conducted for one gr ound spray application for melon subgroup 9A use at a rate of 0.3 lb
a.i./A per year

.

The estimated drinking water concentrations (EDWCs) for tier 1 models are listed in Table 1

. These values are lower than the previously reported EDWC of 27 8.9 μg/L for acute and chronic

exposure s for surface water based on rice scenario and 4.8 μg/L for acute and chronic exposure s

for ground water based on turf scenario (USEPA 2010a , DP 362654 )

. Therefore, the previous ly

### recommended EDWCs should be retained for drink ing water exposure assessment for human

health risk assessment purposes.

Table 1 . Tier I EDWCs for Imazosulfuron for Melon Crop Subgroup 9A and Tuberous and C orm Subgroup 1C uses

Drinking

Water Source Model s Application

rate (lbs

a

. i

. /A/year) Application

Frequency Acute ( μ g/L ) Chronic ( μ g/L )

Surface water F IRST 0.15 2 27.0 8.9

0.30 1 25.1 8.2

Groundwater SCI

- GROW 0.15

0.30 2

1 0.4

0.4 0.4

0.4



### 1.1 Drinking Water Exposure Modeling

The EDWCs were generated using EFED’s standard suite of models. Since there is no
modification of input parameters for FIRST and SCIGROW models, detailed description of
models and inputs parameters can be obtained from the previous assessment (USEPA, 2010 a

,. However, i nputs for FIRST in Table A

- 1 and for SCIGROW in Table A

- 2 as well as output s of

FIRST and SCIGROW models for proposed uses were provided in the Appendix A.
Descriptions of all executable versions of current models used in drinking water expos ure can be

obtained from URL link ( http://www.epa.gov/oppefed1/models/water/ ).

Standard percent cropped areas (PCA) were used for proposed uses as estimates of the extent of
watershed on which crops is grown. The default agricultural PCA of 1.0 was used for the
proposed uses because imazosulfuron can be used for agricultural and non

- agricultur al settings

(USEPA 2010b).

1.2 Monitoring Data

There were no national

- scale monitoring data available for this new chemical assessment.

1.3 Drinking Water Treatment

There is no available information on the drinking water treatment effects on imazosulfuron.

2 C onclusion s

The estimated drinking water concentrations (EDWCs) for surface water and groundwater are

lower t han the previously reported EDWC of 278.9 μg/L for acute and chronic exposure s for

surface water based on rice scenario and 4.8 μg/L for acute and chronic exposures for ground

water based on turf scenario (USEPA 2010a, DP 362654)

. Therefore, the previously
recommended EDWCs should be retained for drinking water exposure assessment for human
health risk assessment purposes.

### The estimated concentrations provided in this assessment are conservative estimates of

imzosulfuron concentrations in untreated drinking water. A major source of uncertainty is the

nature of the non

- extractable residues formed during degradation in soils. Non

- extractable

residues were identified at maximums of 33

- 88 % of applied radioactivity in aerobic soil, aerobic
and ananerobic aquatic metabolism studies. The non

- extractable residues are uncharacterized and
it is uncertain whether they consist of degradates of risk concern. Under sterile conditions these

non

- extractables were not formed suggesting that the formation of them is microbia lly mediated.

If dietary risks require refinement, higher tiered models and modeling scenarios can be utilized

to characterize EDWCs upon request. Appendix A

Table 3. FIRST (v 1.1) input parameter values for total residue a of imazosulfuron applied by ground spray



### Parameter Value Source Comments

Application Rate (lb a.i./A) 0.3 As per V

- 10142 label

Direction ---

Number of Applications 2 ( Crop subgroup

1C) )

1 ( Crop subgroup

9A ) As per V

- 10142 label

Direction ---

Minimum Application
Intervals (days) 45 ( Crop subgroup

1C) ) As per V

- 10142 label

Direction For Ground Application

Soil Partitioning Coefficient

(K f oc ; ml/g

oc ) 98 MRID 47305122 lowest non

- sand value b

Aerobic Soil Metabolism t 1/2 (d) 2 07.15 MRID 473051

- 17

MRID 477668

- 01 90 th percentile upper confidence

bound on the mean half

- life of

total toxic residue of

imazosulfuron

Wetted in? No foliar applied As per V

- 10142 label Direction

Depth of Incorporation

(inches) 0 foliar applied As per V

- 10142 label Direction

Method s of Application Ground spray As per V

- 10142 label

Direction As per V

- 10142 label Direction

Percent Cropped Area 0.87 National default Input parameter guidance

(USEPA, 2002)

Solubility in Water (mg/L) 419 Product chemistry data Input parameter guidance

(USEPA, 200 9 )

Aerobic Aquatic Metabolism

t 1/2 (d) 192.03 MRID 476397

- 02

MRID 476791

- 05 90 th percentile upper confidence

bound on the mean half

- life of

total toxic residue of

imazosulfuronTable 3. FIRST (v 1.1) input parameter values for total residue a of imazosulfuron applied by ground spray



### Parameter Value Source Comments

Hydrolysis t 1/2 at p H 7 .0
(days) 0 MRID 473051

- 19 Stable to hydrolysis @ pH 7.0

Aquatic Photolysis t 1/2 (d) 61.69 MRID 473051

- 20 90 th percentile upper confidence

bound on the mean of IM and
PM rings of imazosulfuron

a = Residues of concern (Parent plus degradates, i.e., HMS, IPSN, UDPM, ADPM and SDPM) recommended by
Residues of Concern Knowledgebase Subcommittee (ROCKS)

b

= A ccording to Guidance for selecting input parameters in modeling for environmental fate and tr ansport of
pesticides. Version II. October , 200 9

.

Table 4 . SCIGROW 2.3 input parameter values for total residue of Imazosulfuron applied by ground spray.

Parameter Value Source Comments

Maximum Application
Rate (lb a.i./A/application) 0. 67 Ground Application As per V

- 10142 label Direction

Maximum Number of
Applications per Year 2 Ground Application As per V

- 10142 label Direction

Aerobic Soil Metabolism

Half

- life (d) 94.3 MRID 473051

- 22 Mean Value a

Organic Carbon Partition

Coefficient (K f

oc , ml/g

oc ) 98 MRID 473051

- 17 Lowest non

- sand value a

a = A ccording to Guidance for selecting input parameters in modeling for environmental fate and transport of

pesticides. Version II. October , 200 9

.

### References

Environmental Fate and Effects Division. 200 9 . Guidance for Selecting Input Parameters in
Modeling the Environmental Fate and Transport of Pesticides, Version II. U. S. Environmental
Protection Agency. Washington, D.C. http://ww w.epa.gov/oppefed1/models/water/

US EPA . 20 10a. 2010. Tier I Drinking Water Assessment for the Section 3 Proposed
Registration of Imazosulfuron on T urf, Tomato, Peppers (Bell and Non

- bell) and Rice (DP

362654 )

US EPA

. 20 10b

. Guidance on development and use of the index reservoir in drinking water

exposure assessment. http://www.epa.gov/oppefed1/models/water/index_reservoir_dwa.html

### Appendix A

Surface water (FRIST)

**Ground Application** 

RUN No. 1 FOR Imazosulfuron ON Melon * INPUT VALUES *

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

RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .300( .300) 1 1 98.0 419.0 GROUND( 6.4) 100.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

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

207.20 2 N/A 61.69

- 7649.56 192.03 187.33

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

------------------------- ------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

--------------------------------------------------------------------
26.972 8.863

RUN No. 2 FOR Imazosulfuron ON Tuberous * INPUT VALUES *

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

RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROP PED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .150( .279) 2 45 98.0 419.0 GROUND( 6.4) 100.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

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

207.20 2 N/A 61.69

- 7649.56 192.03 187.33

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

----------------------------------------------------------- --------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

-------------------------------------------------------------------- 25.082 8.241

### Ground water

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:Imazosulfuron

time is 8/15/2012 10:57:46

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

Application Number of Total Use Koc Soil Aerobic

rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------
0.150 2.0 0.300 9.80E+01 94.3

------------------------------------------------------------------------ groundwater screening cond (ppb) = 3.99E

- 01

************************************************************************

SciGrow version 2.3

chemical:Imazosulfuron

time is 8/15/2012 10:58: 0

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

Application Number of Total Use Koc Soil Aerobic

rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------- -----------------------------------------------------------------
0.300 1.0 0.300 9.80E+01 94.3

------------------------------------------------------------------------ groundwater screening cond (ppb) = 3.99E

- 01

************************************************************************