UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 080805

DP Barcode: 357096, 357099

Date: June 19, 2009

MEMORANDUM

SUBJECT: Prometryn (CAS Reg. No. 7287-19-6) Tier I Drinking Water Assessment

for the Proposed New Uses on Carrots, Okra, Parsley, Cilantro, Celeriac, 

and Leafy Petioles

FROM: Silvia C. Termes, Chemist

Environmental Fate and Effects Division

Environmental Risk Branch III

TO: Barbara Madden

Risk Integration, Minor Use & Emergency Response Branch

Registration Division

THRU: Dana Spatz, Branch Chief

Environmental Fate and Effects Division

Environmental Risk Branch III

The Environmental Fate and Effects Division has completed a Tier I Drinking Water 

Assessment for registration of proposed new uses on carrots, okra, parsley, cilantro, 

celeriac and leafy petioles. These proposed new uses have been included in the existing 

labels of two end-use products containing prometryn as the active ingredient:

Caparol 4L ( 44.4% prometryn; EPA Reg. No.100-620; Syngenta )

Prometryn 4L Herbicide (44.4% prometryn by weight; EPA Reg. No.66222-15; 

Makhteshim Agan of North America, Inc). 

The exposure concentrations in drinking water drawn from surface water were estimated 

using the Tier I simulation FIRST (Version 1.1.1). Concentrations of prometryn in 

ground water were estimated using the Tier I SCI-GROW (Version 2.3) regression 

model. This assessment addresses concentrations of parent only; no degradates were 

included.

1
Results of Tier I Estimates (FIRST and SCI-GROW)

Table 1 summarizes the Tier 1 estimated concentrations in surface and ground water. 

Application information was extracted from the proposed labels.

Table 1. Estimated Concentrations of Prometryn in Drinking Water Drawn from 

Surface Water (FIRST) and from Ground Water (SCI-GROW)

Crop Application 

Information

Peak Day (acute)

Concentration, μg/L

Surface water

Annual Average 

(Chronic) Conc.,

μg/L, Surface water

Ground 

Water, 

μg/L

Carrots

3 Applications @ 2 

lb ai/acre, 30 days 

apart, ground

377.4 157.9 23.2

Okra 1 application @ 1.5

lb ai/acre, ground

96.7 40.5 6.0

Cilantro 1 application @ 1.6 

lb ai/acre, ground

103.2 43.2 6.2

Parsley

3 applications at 0.5 

lb ai/acre, 30 days 

apart, ground

94.3 39.5 5.8

Celeriac 1 application @ 4 lb 

ai/acre, ground

257.9 107.9 15.5

Leafy Petioles 1 application @ 2 lb 

ai/acre, ground

129.0 54.0 8.0

Cotton 1 application @ 2.8 

lb ai/acre, aerial, 

0.20 PCA

42.0 17.8 11.2

Table 2 summarizes the exposure modeling input parameters.

Table 2. Model Input Parameters

Physical-chemical Properties and 

Environmental Fate Input parameters

Available Data Selected Value for 

Modeling

Source

Molecular Weight , g/mole 241.35 241.35 Product chemistry

Solubility in Water, mg/L 33 33 Product chemistry

Vapor Pressure (25 deg) 1.6E-6 torr 1.6 E-6 torr Product chemistry

Henry’s Law Constant, atm-m3-mole-1 N/A 9.1 E-9 (est.) Estimated (EPIWin, 

Version 4.0)

Hydrolysis half-life, days Stable 0 MRID495737-04

Photolysis in Water, days Stable 0 MRID495737-04

Aerobic Soil Metabolism half-life. days 270 days (1-soil) 3x 270

810 days (as per 

Input Parameter 

Guidance)

MRID 4833801

Anaerobic Aquatic Metabolism half-life N/A - N/A

Aerobic Aquatic Metabolism Half-life N/A 2x 810

1620 days (as per 

Input Parameter 

Guidance)

N/A

Sorption Coefficients, Koc Sand: 246

Loamy sand: 169

Silt loam: 117

Silty clay loam: 448

244 (as per Input 

Parameter Guidance)

MRID 00148338

2
Summary of the Environmental Fate of Prometryn

Prometryn is a methylthio-(symmetric) triazine. The chemical names (CAS and IUPAC) 

are presented below together with the CAS Registry Number and chemical structure:

U.S. EPA PC Code: 080805

CA DPR Chemical Code: 502

IUPAC: N2

,N4-diisopropyl-6-methylthio-1,3,5-triazine-2,4-diamine

CAS: N2,N4-diisopropyl-6-methylthio-1,3,5-triazine-2,4-diamine

CAS Reg. No.: 7287-19-6

Chemical Formula: C10H19N5S

SMILES: CSc1nc(NC(C)C)nc(NC(C)C)n1

Chemical Structure:

Metabolites of Prometryn

Name: Prometryn aerobic soil metabolite (27% after one year incubation)

CAS Name: 1,3,5-Triazin-2(1H)-one, 4,6-bis((1-methylethyl)amino)-

IUPAC: 2,4-bis(isopropylamino)-6-hydroxy-s-triazine

CAS Reg No. 7374-53-0

3
N

NH2

N

H

S N N

H3C

CH3

CH3

Name: Prometryn aerobic soil metabolite (1.1% after one year incubation)

IUPAC: 2-amino-4isopropylamino-6-methylthio-s-triazine (GS-1154)

The environmental fate properties of prometryn, along with the major and minor 

degradates detected in the submitted environmental fate and transport studies are 

presented in Table 3.

Table 3. Environmental Fate and Transport Behavior of Prometyrn

Study Value Major Degradates

Minor Degradates

MRID # Study 

Classification

Abiotic 

Hydrolysis

Stable at pH 5, 7, and 9 None 49573704 Acceptable

Direct Aqueous 

Photolysis

Stable None 49573705 Acceptable

Soil Photolysis Stable None 49573706 Acceptable

Aerobic Soil 

Metabolism

t 1⁄2 270 days; (One soil)

Sandy Soil

2,4-bis(isopropylamino)-6-

hydroxy-s-triazine (GS11526, 27% of the applied 

radioactivity after 360 days

2-amino-4isopropylamino6-methylthio-s-triazine 

(GS-1154); 1.1% at 30 days

00148338 Acceptable

Anaerobic Soil 

Metabolism

t 1⁄2 90 days

Stable

41155509 Acceptable

Anaerobic 

Aquatic 

Metabolism

No data submitted No data - N/A

Aerobic Aquatic 

Metabolism

No data submitted No data - N/A

163- Mobility in 

Soil, Batchequilibrium 

Adsorption/

Desorption

K Freundlich, Adsorpotion

0.86 (agricultural sand) to 

3.18 (silty clay loam); 

add other soils

GS 11526 mobile to very 

mobile (Freudlich Kads 7.1 

to 0.5)

GS-11354 very mobile 

(Freudlich Kads 0.63-1.9)

49573713

41875901

41875902

41875903

41875904

41875905

Acceptable

4
Study Value Major Degradates

Minor Degradates

MRID # Study 

Classification

163-2 Volatility 

from Soil 

(Laboratory)

Sand soil

Volatility was minimal, 

0.99% prometryn 

volatilized by 30 days

No 41875906 Acceptable

Terrestrial Field 

Dissipation

t 1⁄2 Cotton CA, 105 days

t 1⁄2 Cotton CA 71 days

t 1⁄2 Cotton TX 14-30 

days

t 1⁄2 Cotton TX 14 days

Prometryn was not detected 

below 45 cm

CS-11354 detected at 120 

cm soil depth

Acceptable (for 

flowable 

concentrate)

Aquatic Field 

Dissipation

No data Not applicable Not 

applicable

N/A

According to the submitted physical-chemical and environmental fate data, the 

degradation of prometryn is driven by microbial (biotic) activity and not by abiotic 

processes; however, biotransformation is slow. The major biotransformation product is 

GS-11526. The low Freundlich adsorption coefficient of prometryn suggests that the 

chemical has the potential to run off and/or leach to ground water. Prometryn is stable to 

hydrolysis and direct photolysis in aqueous media.

Prometryn and its degradates are very mobile to mobile in soil. Potential transport 

mechanisms include runoff to surface water, leaching to ground water, spray drift, and 

secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or 

more distant ecosystems. 

The US Geological Survey (USGS) has reported data on the presence of pesticides in rain 

and wet deposition in four USA agricultural watersheds. Among other pesticides, 

prometryn was detected in rain and wet deposition in California.

5
Modeling Outputs - FIRST

CARROTS

A. 3 applications 30 days apart @ 2 lb ai/acre

RUN No.1330 FOR Prometryn ON Carrots * INPUT VALUES *

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

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

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

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

.000( 5.849) 3 30 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

 377.368 157.873

B. One application @ 2 lb ai/acre

RUN No. 12 FOR Prometryn ON Carrot * INPUT VALUES *

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

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

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

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

2.000( 2.000) 1 1 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

 810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

128.977 53.952

6
C. Two applications@ 2 lb/acre, 30 days apart

RUN No. 122 FOR Prometryn ON Carrots * INPUT VALUES *

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

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

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

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

2.000( 3.949) 2 30 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

 810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

254.740 106.565

OKRA

A. One application at 1.5 lb ai/acre

RUN No. 21 FOR Prometryn ON Okra * INPUT VALUES *

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

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

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

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

.500( 1.500) 1 1 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

96.733 40.464

7
b. Two applications @ 0.75 lb ai 30 days apart

RUN No. 22 FOR Prometryn ON Okra * INPUT VALUES *

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

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

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

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

.750( 1.481) 2 30 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

95.527 39.962

CILANTRO

Single application @ 1.6 lb ai/acre

RUN No. 31 FOR Prometryn ON Cilantro * INPU

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

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

 ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) ARE

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

.600( 1.600) 1 1 244.0 33.0 GROUND( 6.4) 87.

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.)

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

810.00 2 N/A .00- .00 ******

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 J

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

103.182 43.161

8
PARSLEY

A. Single application @ 0.5 lb ai/acre

RUN No. 41 FOR Prometryn ON Parsley * INPUT VALUES *

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

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

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

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

.500( .500) 1 1 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

32.244 13.488

B. Two appications @0.5 lb ai/acre, 30 days apart

RUN No. 42 FOR Prometryn ON Parsley * INPUT VALUES *

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

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

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

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

.500( .987) 2 30 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

63.685 26.641

9
C. Three applications @ 0.5 lb ai/acre, 30 days apart

RUN No. 43 FOR Prometryn ON Parsley * INPUT VALUES *

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

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

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

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

.500( 1.462) 3 30 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

94.342 39.468

CELERIAC

Single application @ 4 lb ai/acre

RUN No. 51 FOR Prometryn ON Celeriac * INPUT VALUES *

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

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

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

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

4.000( 4.000) 1 1 244.0 33.0 GROUND( 6.4) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

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

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

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

 810.00 2 N/A .00- .00 ****** 1620.00

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

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

 257.954 107.903

10