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Chlorsulfuron Focus Meeting Summary

December 6, 2012 

11:00am - 12:30pm

Attendees

E.I. DuPont de Nemours and Company (DuPont): Aldos Barefoot, Dave W. Saunders, Craig 

M. Alford, Cecilia Much Hirata, Richard J. Ambrose

Environmental Protection Agency (EPA or Agency): Kaitlin Keller (PRD), Patricia Parrott

(PRD), Monica Hawkins (HED), Sheila Piper (HED, Christine Olinger (HED), Mary Clock-Rust 

(EFED), Ed Scollon (EFED), Katrina White (EFED), Cynthia Doucoure (BEAD), Stephen 

Smearman(BEAD)

Objective

The purpose of the meeting was for members of the EPA’s Pesticide Re-evaluation Division 

(PRD), Environmental Fate and Effects Division (EFED), Biological and Economic Analysis 

Division (BEAD), and Health Effects Division (HED) to meet with DuPont, a technical 

registrant for chlorsulfuron, for the following reasons: 1) discuss European Union studies on 

chlorsulfuron degradates that EPA requested be submitted for review; 2) discuss annual usage 

information needed for the registration review human health and ecological risk assessments; 3)

discuss use of chlorsulfuron on uncultivated areas and intermittently flooded areas as well as 

potential label clarifications for these uses; 4) discuss label language to reduce spray drift. 

Discussion

Degradate and Metabolite Information

On October 25, 2012, EPA provided DuPont with a list of degradate studies submitted to the 

European Union (EU) to support European registrations of chlorsulfuron and requested that 

DuPont submit these studies for review. On November 29, 2012, DuPont submitted six EU 

studies on chlorsulfuron degradates as requested for the registration review of chlorsulfuron. 

DuPont provided an overview of the findings in these studies in the meeting as well as an 

overview of the environmental fate and physical chemistry properties of chlorsulfuron. EPA 

indicated it would be useful to have the foreign soil classifications on studies submitted that were 

conducted on foreign soils using the guidance available at: 

http://www.epa.gov/oppfead1/international/naftatwg/projects/regulatory/soil-crosswalks.pdf.

Use/Usage Information

DuPont provided a list of active registrations for the EPA to cross-check with those EPA 

believes are active registrations. DuPont also provided usage information in terms of amounts 

used in pounds per year nationally and regionally by product and use category (in terms of cereal 

products, range and pasture products, and vegetation management), noting that this information 

can be broken down by state and will be submitted to the Agency. EPA agreed that a breakdown 

of the data by state would be helpful. DuPont also indicated that they are working toward 

standardizing placement of application use information on all DuPont chlorsulfuron labels and 

will provide EPA with a master spreadsheet that tabulates all chlorsulfuron use information, such 

as use sites, application timing, application methods, single maximum and seasonal maximum 

uses rates and minimum retreatment intervals.
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Label Clarifications

DuPont provided an overview of chlorsulfuron products used and the intended use definition for 

uncultivated areas. EPA and DuPont agreed that DuPont products are not intended for use in 

residential settings. EPA explained that unless products specifically prohibit residential use, 

EPA would conduct a residential assessment because certain chlorsulfuron uses, such as 

ornamentals and various uncultivated area sites, could be used by residential homeowners. 

DuPont agreed to work with EPA to develop appropriate language for labels that would prohibit 

residential use prior to the risk assessment phase of registration review. 

Additionally, DuPont further clarified the intermittently flooded areas use of chlorsulfuron. 

DuPont stated that the intended use is primarily in the Western United States as a spot treatment 

in areas that would flood during spring snow melt and runoff. Moisture in these areas makes 

them prone to noxious weeded which landowners are required by state regulators to control. 

Based on the intended use for flooded areas, EPA and DuPont agreed that label language could 

be better defined. EPA also explained that more descriptive use sites could help reduce 

conservative assumptions in ecological risk assessments. Additionally, EPA requested more 

information on the size of the spot treated for intermittently flooded areas. DuPont agreed to 

work with the Agency to develop label language that more accurately defines this use and to 

provide information on the size of a spot treatment for this use. 

Spray Drift

DuPont reviewed spray drift requirements and recommendations required by the 2005 

Reregistration Eligibility Decision (RED) and indicated that most products do have all 

appropriate spray drift mitigation on the labels. Two products are missing the requirement for a 

maximum boom height of 10 feet above target vegetation for aerial applications. However, 

DuPont noted that this is the default height in practice. DuPont committed to ensuring that the 

two product labels without this language are updated prior to the registration review risk 

assessment phase. 

Follow-up

 DuPont will provide the foreign soil classification for studies submitted that were 

conducted on foreign soils.

 DuPont will provide EPA with overall annual chlorsulfuron usage by product broken 

down by state and EPA Region.

 DuPont will provide EPA with a master spreadsheet of all DuPont chlorsulfuron product 

use information. 

 DuPont will provide EPA with the size of a typical spot application of chlorsulfuron on 

intermittently flooded areas.

 DuPont will ensure that spray drift label language is updated on the two DuPont products 

currently missing the 10 ft. aerial application maximum boom height restriction.

 EPA will work with DuPont to develop revised label language to clearly prohibit 

residential use of chlorsulfuron and better define intermittently flooded areas.