|New York State Department of Environmental
Division of Solid & Hazardous Materials
50 Wolf Road, Albany, New York 12233-7254
Phone: (518) 457-6934 FAX: (518) 457-0629
|March 3, 2000|
RETURN RECEIPT REQUESTED
Thomas L. Woods, Ph.D.
Zeneca Ag Products
1800 Concord Pike
P.O. Box 15458
Wilmington, DE 19850-5458
Dear Dr. Woods:
Re: Registration of A Major Change in Label for the Active Ingredient - Sulfosate Contained in the Pesticide Product Touchdown 5 Herbicide (EPA Reg. 10182-429)
The New York State Department of Environmental Conservation (the Department) has completed its review of your application, received October 13, 1999, for the registration of an increase in the seasonal rate of use for Touchdown 5 Herbicide from the current four lbs/ai/acre/year (except for corn) to eight lbs ai/acre/year. We have concluded that use of this product at the higher rate is not likely to pose unacceptable risks to public health or environmental resources in New York State.
Sulfosate was registered on January 20, 1999 for use in New York as a nonselective foliar herbicide for control of a broad spectrum of emerged grass and broadleaf weeds, both annual and perennial, in corn (field, pop and seed), soybeans, bearing and non-bearing crops (berries, fruits, nuts, vegetables, and vines), certain non-crop areas, and fallowland, and for postharvest use. On June 1, 1999 use on wheat and pome fruits was added and on September 3, 1999 use on glyphosate-tolerant soybeans and preharvest use on all soybeans was approved.
In a United States Environmental Protection Agency’s (USEPA) Health Effects Division (HED) review dated September 21, 1998, HED issued a review concluding that there were sufficient data to raise the seasonal application use rate from four to eight lbs/ai/acre/year (except corn). Subsequently, the EPA-stamped accepted label was amended (on June 8, 1999) to reflect this rate increase. The single maximum application rate remains at or below four lbs/ai/acre.
The application was determined complete for purposes of review on November 29, 1999 and the registration decision date was set at April 27, 2000.
No adverse impacts to fish or wildlife resources are anticipated through the labeled increased in use of sulfosate. However, runoff in those cases where rain would follow closely after application was an issue during our review. Sulfosate was previously reviewed (see our January 20, 1999 registration letter) and the reviewers noted that sulfosate is highly soluble in water (4.3 g/L), so the potential would be great for large volumes of sulfosate to be removed from the ground if application were followed shortly by a runoff event.
A new terrestrial field dissipation study and an Environmental Fate Branch (EFB) memorandum were submitted with the application. Although not all of the environmental fate information requested by staff in previous reviews was submitted, memoranda from the USEPA were submitted that summarized the studies and gave the USEPA’s approval of the data generated.
In the new field dissipation studies of a fine sandy loam soil treated with 10.6 lb ai/acre, the half-lives of TMS and its degradate PMG were 56 and 57 days, respectively. Neither of these were found below the seven-inch soil depth. The PMG degradate AMPA was detected only in the 0 to 3.5 inch depth. In a silty clay loam treated with 8.0 lb ai/acre, the TMS and PMG half-lives were 32 and 72 days, respectively. Neither of these were found below the seven-inch soil depth. The PMG degradate AMPA was detected only in the 0 to 3.5 inch depth. In a sandy loam soil in California treated with 8.0 lb ai/acre, the TMS and PMG half-lives were 18 and 13 days, respectively. TMS, PMG and AMA were not found below the three-inch soil depth.
Sulfosate appears to be readily degraded by soil microbes with a t1/2 of 48 to 72 hours to AMPA, which is then further degraded to carbon dioxide. The TMS moiety appears to biodegrade fairly rapidly, also, with a t1/2 of 72 hours.
Computer modeling was done with LEACHP, using sandy Riverhead soil, a kd of 3.67, a half-life of 14 days (from the aerobic metabolism study) and an application rate of 8.0 lb ai/acre/year, applied as two applications. Sulfosate falls under the "unspecified organic contaminants" drinking water standard of 50 micrograms per liter (10 NYCRR Part 5 - Public Water Systems). The model projected cyclical peaks of just under 0.6 ppb which does not project leachate concentrations approaching the trigger value of 25 ppb (or half the drinking water standard).
The USEPA commented in their review that even though sulfosate is highly water soluble, it appears that TMS, PMG and the degradate AMPA have a low potential to move to groundwater due to fairly fast microbial degradation (72 hours) and the adsorptive characteristics as demonstrated in the laboratory and in field studies. Available field data indicate that sulfosate adsorbs fairly strongly to soil and would not be expected to move vertically below the six-inch soil layer. However, sulfosate does have a limited potential to contaminate surface waters if a runoff event were to occur shortly after application. Sulfosate could be readily washed from the application area and transported to local surface waters, where it may either photodegrade to carbon dioxide or persist for some time (up to 77 days at pH 7), depending on light sensitization and water pH.
The Touchdown label warns the user that rain following an application may make reapplication necessary. Therefore, we anticipate that economic considerations would ensure that the average grower is not likely to use this product if rain is expected for the area.
Therefore, the Department accepted for registration the increase in the maximum use rate of Touchdown 5 Herbicide (EPA Reg. No. 10182-429) to 12.8 pints per acre per year (or 8.0 lb ai/acre/year).
Enclosed is a stamped accepted copy of the acceptable label for your records. If you have any questions, please contact Maureen Serafini, Chief of our Pesticide Product Registration Section, at (518) 457-7446.
Stephen Hammond, P.E.
Division of Solid & Hazardous Materials
cc: w/enc.- G. Good/W. Smith, Cornell PMEP
R. Zimmerman/R. Mungari, NYS Dept. of Ag & Mkts.
N. Kim/D. Luttinger, NYS Dept. of Health