DUPONT SULFOMETURON METHYL

EPA FOCUS MEETING

ENVIRONMENTAL FATE AND EFFECTS

AQUATIC AND AVIAN SPECIES TESTING

September 26, 2012
Guideline 835.6100 Terrestrial Field Dissipation Study: 

Supporting ECM & ILV

 We concur with EPA comment. Separate soil/water 

analytical methods are available for parent compound and 

metabolites IN-X0993, IN-D5803 and IN-581. If requested, 

DuPont will refine current methods to single parent + 

metabolites method, and provide method ILV.
Guideline 835.4100 – Aerobic Soil Metabolism 

Acceptable laboratory data (route and rate of degradation) for 

aerobic soil metabolism of SMM is available for Keyport soil. 

DuPont is of the position that additional rate data may be obtained 

from available field data because for all SUs, field data are very 

consistent with laboratory data :

SU

Lab Rate Range (DegT50,

days) [Number of Soils]

Field Rate Range (DT50, days) 

[Number of SItes]

Sulfometuron 23, 29 [1]1 12 – 23 [4]2

Thifensulfuron 0.5 – 7 [6] 1 – 10 [12]

Metsulfuron 9 – 90 [14] 37 – 68 [4]

Flupyrsulfuron 8 – 22 [6] 8 – 23 [4]

Chlorsulfuron 12 – 71 [5] 3 – 70 [5]

Rimsulfuron 21 – 40 [4] 6 – 18 [8]

1. Two separate studies run on Keyport soil

2. Field soil types characterized as silty clay loam (2 sites), clay (1 site) and sandy loam (1 site)
Guideline 835.4100 – Aerobic Soil Metabolism 

(continued) 

For sulfometuron methyl, field data on multiple soil types are 

consistent with laboratory data; overall data set includes 4 distinct 

soil types

SU

Laboratory DegT50 

(days); Soil Type

Field Data

Field DT50 

(days) Soil Type Soil pH Soil %OC

Sulfometuron 23, 291; silty loam, 

pH 6.4, 1.6% OC

12 silty clay loam 6.7 0.6

14 silty clay loam 6.8 1.0

13 clay 7.9 1.3

23 sandy loam 7.8 0.7

1. Two separate studies run on Keyport soil
Guideline 850.1025 – Acute toxicity estuarine/marine 

invertebrate (bivalve); 

Guideline 850.1035 – Acute toxicity estuarine/marine 

invertebrate (mysid); 

Guideline 850.1075 – Acute toxicity estuarine/marine 

fish

We accept that the variability in these studies leads to 

their classification as supplemental instead of core
Guideline 850.1350 – Estuarine/marine invertebrate life cycle

We agree with EFED to characterize toxicity to estuarine/ 

marine invertebrates using toxicity data for freshwater 

invertebrates

Study Sulfometuron Chlorsulfuron Metsulfuron Rimsulfuron

Acute Daphnia magna

(LD50) (freshwater)

>150 mg/L >112 mg/L >120 mg/L >243 mg/L

Acute Crassostrea 

virginica (LD50) 

(estuarine/marine)

>38.2 mg/L 385 mg/L - >120 mg/L

Acute Mysidopsis 

bahia (LD50) 

(estuarine/marine)

>44.8 mg/L 89 mg/L - >110 mg/L

Chronic Daphnia 

magna (NOEC) 

(freshwater)

97 mg/L 20 mg/L 150 mg/L 26 mg/L

Life Cycle Daphnia 

magna (NOEC) 

(freshwater)

- - 100 mg/L -
Guideline 850.1400 – Estuarine/marine and freshwater 

fish early-life stage

We agree with the suggestion from EFED to characterize 

toxicity to estuarine/marine and freshwater fish using toxicity 

data for other sulfonylureas with a similar toxicity profile and 

the same mode of action

Study Sulfometuron Chlorsulfuron Metsulfuron Rimsulfuron

Acute Lepomis 

macrochirus

(LD50) (freshwter)

>150 mg/L >128 mg/L >119 mg/L >250 mg/L

Acute 

Oncorhynchus 

mykiss (LD50) 

(freshwater)

>148 mg/L >122 mg/L >113 mg/L >180 mg/L

Acute Cyprinodon 

variegatus (LD50) 

(saltwater)

>45 mg/L >980 mg/L - >110 mg/L

Early life stage 

Oncorhynchus 

mykiss (NOEC) 

- 32 mg/L 4.5 mg/L 125 mg/L
Guideline 850.2100 – Avian oral toxicity, passerine species

SMM Mallard Duck Acute Oral Toxicity – LD50 >5000 mg/kg

SMM Mallard Duck Dietary Toxicity – LD50 >5000 mg/kg, NOEC – 5000 mg/kg

SMM Northern Bobwhite Dietary Toxicity – LD50 >5620 mg/kg, NOEC – 5620 mg/kg

The maximum dose-based EEC calculated by T-REX is 76.88 mg/kg- bw (small bird with short grass diet)

Passerine species would need to have an LD50 an order of magnitude 

more sensitive than ducks and quails in order to be of concern

Sulfometuron Methyl is practically non-toxic to birds and we 

request that this study be waived
Guideline 850.2300 – Avian reproduction, upland game 

and waterfowl species

We agree with EFED to characterize avian reproduction toxicity 

using data for other sulfonylureas with a similar toxicity profile 

and the same mode of action

Study Sulfometuron Chlorsulfuron Metsulfuron Rimsulfuron

Acute Mallard 

(LD50)

>5000 mg/kg >5000 mg/kg >2510 mg/kg >2250 mg/kg

Acute Bobwhite 

(LD50)

- >5000 mg/kg - >2250 mg/kg

Dietary Mallard 

(LC50)

>5000 mg/kg >5000 mg/kg >5620 mg/kg >5620 mg/kg

Dietary Bobwhite 

(LC50)

>5620 mg/kg >5620 mg/kg >5620 mg/kg >5620 mg/kg

Reproduction 

Mallard (NOEL)

- 961 mg/kg 1000 mg/kg 1250 mg/kg

Reproduction 

Bobwhite 

(NOEL)

- 907 mg/kg 1000 mg/kg 1250 mg/kg
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Additional Information: Comparison of SU Aerobic Soil Metabolism