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Foramsulfuron - Registration of Option Corn Herbicide 5/03

New York State Department of Environmental Conservation
Division of Solid & Hazardous Materials

Bureau of Pesticides Management
Pesticide Product Registration Section
625 Broadway, Albany, New York 12233-7257
Phone 518-402-8768     FAX 518-402-9024

May 2, 2003


Ms. Linda Aschbrenner
State Registration Specialist
Bayer CropScience
PO Box 12014
Research Triangle Park, North Carolina 27709

Dear Ms. Aschbrenner:

Re: Registration of One New Pesticide Product, Option Corn Herbicide (EPA Reg. No. 264-685), Which Contains the New Active Ingredient Foramsulfuron

    The New York State Department of Environmental Conservation (Department) has reviewed your application, received July 12, 2002, and additional information, received October 21, 2002, to register one new pesticide product, Option Corn Herbicide (EPA Reg. No. 264-685), in New York State. The product contains the new active ingredient foramsulfuron (chemical code 122020).

    The application was deemed complete for purposes of review on December 11, 2002 and a registration decision is due by May 9, 2003.

    Option Corn Herbicide (EPA Reg. No. 264-685) is a sulfonylurea herbicide which is labeled for ground application as a foliar spray in field corn for the control of annual and perennial grass and broadleaf weeds. The maximum application rate is 0.08 pounds of foramsulfuron per acre per year.

    The Department has reviewed the information supplied to date in support of registration of the new product Option Corn Herbicide (EPA Reg. No. 264-685).

    The New York State Department of Health (DOH) stated that neither foramsulfuron nor Option Corn Herbicide was very acutely toxic in animal studies by the oral, dermal or inhalation routes of exposure. The formulated product was slightly irritating to the skin and eyes (tested on rabbits) and had dermal sensitizing properties (tested on guinea pigs), whereas the active ingredient was not irritating to skin or eyes, and was not a dermal sensitizer.

    Foramsulfuron did not cause effects in any of the subchronic, chronic, developmental and reproductive toxicity studies. All of these toxicity studies were tested at the limit dose of 1,000 milligrams per kilogram body weight per day (mg/kg/day) or greater, except the rabbit developmental toxicity study where the highest dose tested was 500 mg/kg/day. The United States Environmental Protection Agency (USEPA) designated foramsulfuron as "not likely to be carcinogenic to humans" based on a lack of evidence of carcinogenicity in rats and mice, as well as a lack of effects in a number of genotoxicity studies.

    The USEPA did not conduct either worker or dietary risk assessments for foramsulfuron because no significant adverse effects were reported for the subchronic, chronic, developmental and reproductive toxicity studies. In addition, the USEPA exempted foramsulfuron from the requirement of a tolerance.

    There are no chemical specific federal or State drinking water/groundwater standards for foramsulfuron. Based on its chemical structure, this compound falls under the 50 microgram per liter (_g/L) New York State drinking water standard for "unspecified organic contaminants" (10 NYCRR Part 5, Public Water Systems).

    The available information on foramsulfuron and Option Corn Herbicide indicate that they are not very acutely toxic in laboratory animal studies. In addition, foramsulfuron did not cause toxicity in subchronic, chronic, reproductive and developmental toxicity studies at the highest doses tested. The USEPA did not conduct dietary or worker risk assessments on foramsulfuron due to its demonstrated low toxicity. Because the formulated product has shown skin sensitization properties, the product's label cautions that "Prolonged or frequently repeated skin contact may cause allergic reaction in some individuals." To further mitigate exposure, the Option Corn Herbicide label requires the use of personal protective equipment including long-sleeved shirt, long pants and chemical-resistant gloves. Given the above, Option Corn Herbicide use should not pose a significant risk to workers or the general public.

    The Department's Division of Fish, Wildlife & Marine Resources' Bureau of Habitat (BOH) reviewed the information submitted in support of registration of Option Corn Herbicide and stated that they have no objection to registration.

    The Department's groundwater staff stated the following:

Hydrolysis: Hydrolysis of this acidic compound was highly sensitive to pH and temperature, slowing dramatically above pH 5 and with decreasing temperature. The USEPA-calculated half-life was 4.5 days at pH 4, 10.6 days at pH 5, 156 days at pH 7 and 176 days at pH 9. At pHs 4 and 5, degradates AE F153745 and AE F092944 were found at a maximum of 74.7% and 83.3%, respectively. At pHs 7 and 9, degradates AE F130619, AE F092944, AE F148003 and AE 0001082 were found at a maximum of 29.6%, 33.3%, 15.6% and 10.7% respectively. AE F130619 was the only degradate that retained the sulfonylurea bridge.

Photolysis: Foramsulfuron is stable to aqueous and soil photolysis.

Aerobic Soil Metabolism: The combination of this study and several other aerobic soil metabolism studies in different soils and under different experimental conditions of temperature and relative soil moisture satisfy the data requirement for aerobic soil metabolism. Foramsulfuron is relatively short-lived and degradation is bi-phasic. In three soils, the two-compartment DT50 day value was 1.2, 3.5 and 9.5. The two-compartment DT90 day value was 40, 13 and 51 days, respectively. Two major organic metabolites were identified and quantified. AE F130619 was found at 31% of applied radioactivity at day one, and AE F092944 reached 27% of applied at 22 days. AE F130619 appeared to decline rapidly in a few days, and AE F092944 appeared to be persistent in all soils ("half-lives" hundreds of days). The USEPA Pesticide Fact Sheet for Foramsulfuron, dated March 27, 2002, indicates that the parent has an aerobic soil metabolism half-life of 40 days.

Degradate Aerobic Soil Metabolism: Radiolabeled AE F130619 was short lived in the four soils tested in this study. Most striking was the rapid formation of large fractions of unextracted soil residues (up to approximately 100% near the end of the 120 day test period). The major identified metabolite was AE F092944.

Aerobic Aquatic Metabolism: In two different laboratory sediment/water systems, the registrant-calculated two-compartment values at DT50 were 34 and 55 days for non-sterile samples and 87 days and 190 days for sterile samples; the DT90s were 110 and 180 days for non-sterile and 290 days and 634 days for sterile samples. Two major degradates were formed: AE 0338795 up to 25%, and AE F153745 up to 25%. Five minor degradates were formed.

Anaerobic Aquatic Metabolism: Five minor degradates were formed, but no major degradates. The USEPA Pesticide Fact Sheet for Foramsulfuron, dated March 27, 2002, indicates that it has an anaerobic aquatic metabolism half-life of 76 days.

Adsorption/Desorption: Kocs for foramsulfuron were 151 for a silty clay loam, 89 for a loamy sand, 51 for a loamy sand, 38 for sand and 63 for clay. The USEPA Pesticide Fact Sheet for Foramsulfuron, dated March 27, 2002, indicates that it is weakly sorbed to soils.

Degradate Adsorption/Desorption: Kocs for AE F153745 were 63 for a sand soil, 35 for a clay loam soil, 50 for a sandy loam soil, and 48 for a loam soil.

Degradate Adsorption/Desorption: Desorption Phase 2 of the bi-phasic desorption Kocs for AE F130619 were 199 for a sandy loam soil, 186 for a sand soil, 132 for a clay loam soil and 465 for a loam soil.

Degradate Adsorption/Desorption: Kocs for AE F092944 were 211 in a sand, 89, 625 and 663 in loamy sands, 696 and 395 in sandy loams, 11289 in a silt loam and 917 in a silty clay. This degradate was previously know as Hoe 092944.

Lysimeter Study: The mobility of foramsulfuron was studied in an English sand soil. Two lysimeters were prepared and planted with maize the first year, and wheat subsequently. Precipitation was augmented with irrigation. Bromide tracer broke through approximately 4 months after the first application. The maximum amount of tracer occurred at 5 months and 8 months. Collected leachate in the first two years accounted for 42-50% of the total water input. Degradate AE F130619 was present in the leachate at a maximum of 0.005 g ai equivalents/L. No parent or other degradate was detected in the leachate. When the final soil columns were tested, foramsulfuron, AE F099095, AE F 092944 and AE F130619 were present down to the 0-10 cm depth at 0.01-0.15%, 0.74-0.85%, 0.5-0.61% and 0.37-0.53% of the applied respectively, and each were present in the 10-20 cm depth at 0.20% of the applied. Unextracted residues present in the 10-20 cm and 20-30 cm depths were 5.54-10.06% and 1.43-2.95% of the applied, respectively. Total residues present in the maize, wheat and weeds were 0.44-1.67%, 0.01% and 0.61-1.02% of applied, respectively.

Field Dissipation: USEPA found this study to be supplemental and in partial fulfillment of the requirements. Parent foramsulfuran was not found at the four study sites with reviewer-calculated first-order kinetics regression half-lives ranging from 11-18 days.

Label Statements: The following statements appears on the label:
Computer Modeling: Modeling by the Department on Riverhead sand, using 0.08 lb ai/a/yr, a Koc of 89 for both the parent and the degradate (27%) and an aerobic half-life of 40 days projected breakthrough for the parent in the second year, and peaks starting in the second year ranging between 0 and less than 0.03 ppb. The model predicted the degradate AE F092944 had breakthrough at about 4 months, and peaks ranging from less than 0.1 to less than 0.3 ppb. Changing to the field dissipation half-life of 18 days, the model projected breakthrough for the parent in the second year, and peaks starting in the second year ranging between 0 and less than 0.02 ppb. For the degradate, the model projected breakthrough in four months, and peaks starting in the second year ranging from between 0 and 0.2 ppb.

    While this active ingredient has fairly low Kocs and is mobile, the application rate is low and the half-lives are not long. The soil insecticide interaction information indicates that the degradation rate will be slower if the product is used with OP insecticides, which if modeled would indicate persistence and accumulation. However, even if the product is used in conjunction with the above-referenced OP products, it is staff's opinion that the leaching rate would still be very low.

    The Department concludes that Option Corn Herbicide should not have an adverse effect on the health of workers or the general public, the fish and wildlife resources, or the ground and surface water of New York State when used as labeled.

    Therefore, the Department hereby accepts for registration the new product Option Corn Herbicide (EPA Reg. No. 264-685).

    Enclosed are your New York State stamped "ACCEPTED" label and a copy of the Certificate of Registration.

    Bayer CropScience is reminded that if New York State registration is requested for this product or for any other product which contains foramsulfuron with an increased application rate and/or expanded use sites, the product will be considered a Major Change in Labeling and the Department will require an extensive review.

    If you have any questions, please contact Mr. Samuel Jackling, Chief of our Pesticide Product Registration Section, at (518) 402-8768.


Maureen P. Serafini
Bureau of Pesticides Management

cc: w/enc.: N. Kim/D. Luttinger - NYS Dept. of Health
R. Zimmerman/ R. Mungari - NYS Dept. of Ag. & Markets
G. Good/W. Smith - Cornell University, PMEP