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1). Data Waiver Request for Aquatic Field Dissipation Study (835.6200)

BCS comments (pages 26 and 27): 

 Mesosulfuron-methyl has no registered use in aquatic systems. 

 While water soluble, mesosulfuron-methyl degrades fast both under aerobic soil and 

aerobic aquatic conditions, and it is not persistent.

 Mesosulfuron-methyl and major degradates have intermediate or immobile 

characteristics, and in field dissipation studies quantifiable residues were not detected 

below 7.5 to 30 cm depths. 

 Mesosulfuron-methyl has been extensively studied in environmental fate studies and data 

indicate it will not likely persist or move to aquatic environments. 

EFED response: EFED acknowledges BCS’s presentation on environmental fate profile of

mesosulfuron-methyl (page 5 – 22). The submitted data showed that mesosulfuron-methyl is 

persistent with aerobic soil DT50 up to 199 days (MRID 45386425) and with DT50 up to 100 

days in aerobic aquatic system (MRID 45386430). The FAO mobility classification showed 

mesosulfuron-methyl (Koc = 93) and its major degradate, AE F145851, (Koc = 78) (Page 14) are 

highly mobile, which are likely entering the aquatic environments through runoff, erosion or

leaching. EFED concurs that “mesosulfuron-methyl has no registered use in aquatic systems”. 

Not having a direct application to water registered does not automatically exclude a chemical 

from needing this study. EFED is concerned about what happens when the chemical gets into 

water. However, in considering mesosulfuron-methyl has relatively low toxicity to aquatic fish 

and invertebrates and the annual application rate is low, the aquatic field dissipation study will 

not be needed for Registration Review. Therefore, EFED recommends the aquatic field 

dissipation study (835.6200) to be waived.

2). Data Waiver Request for Environmental Chemistry Method (ECM) and Independent 

Laboratory Validation (ILV) Study (850.6100)

BCS comments (page 2): 

 BCS is requesting the data requirements for all degradates except for parent 

mesosulfuron-methyl, and metabolite AE-F092944 be waived (Option 9). Justification 

for this request is included in this package. BCS intends to conduct the study for the 

parent, mesosulfuron-methyl (Option 1; time frame: 12 months). Additionally, as AEF092944 is a common metabolite with foramsulfuron, BCS will submit this data with the 

foramsulfuron DCI data package (Option 4; time frame: 12 months, with foramsulfuron 

data). 

EFED response: BCS’s justification for the ECM/ILV data waiver request was not found from 

the submitted package. EFED reviewed two previous submitted ECM/ILV (MRIDs 46451701 

and 46451702) and concluded that they can only be used for monitoring parent mesosulfuronmethyl in water. A new ECM/ILV, with the major degradates to be included, is recommended. 

Each ECM should be able to analyze both the parent and the major degradates at the same time. 

It is not acceptable for mesosulfuron DCI to have one common degradate AE F092944 to be 

included in the foramsulfuron DCI data package However, foramsulfuron ECM/ILV may 

include parent mesosulfuron-methyl and its major degradates listed below (e.g.: an analytical
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method for multiple chemicals and their degradates). Based on a recent review of newly

submitted aquatic plant toxicity data (USEPA 2014, DP 422361), two major degradates, BCSCV14885 (benzoic acid with guanidine), and BCS-CO60720 (methyl ester of benzoic acid with 

guanidine), are not recommended to be included in the ECM/ILV (water) study. EFED reiterates 

the previous recommendation (USEPA 2013, DP 414767) that the ECM/ILV (850.6100) studies 

(water and soil), including the major degradates, should not to be waived (see below).

1) ECM/ILV (water) (850.6100) - to include the major degradates observed in aquatic 

environments (AE F160459, AE F160460, AE F140584, AE F147447, AE F092944, 

2) ECM/ILV (soil) (850.6100) - to include the major degradates observed in soil 

environments (AE F154851, AE F099095, and AE F092944). 

References

USEPA. 2013. Response to Public Comments on the Mesosulfuron-methyl RegistrationReview Problem Formulation. DP 414767. 6pp

USEPA. 2014. Review of BCS –CO60720 (Degradate of Mesosulfuron-methyl) Vascular 

Aquatic Plant Toxicity Study (MRID 49447202) in Support of Registration Review and 

EFED responses to Registrant’s Data Waiver Request for Vascular Aquatic Plant 

Toxicity Testing with BCS-CV 14885, a Degradation Product of Mesosulfuron methyl. 

DP 422361. 2pp.

Bayer CropScience. 2014. Mesosulfuron-methyl: (EPA Reg Nos. 264-694, 264-802, 264-847, 

and 264-801); 90-Day Response to Generic Data Call-In for Mesosulfuron-methyl 

Generic ID: DCI-122009-1369. MRID 49447200. 42pp.