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Halosulfuron-Methyl - Withdrawal of SLN Application for Sandea™ 11/01

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
E-Mail: ppr@gw.dec. state.

November 8, 2001


Ms. Jean Warholic
Executive Secretary
New York State Vegetable Growers Association, Inc.
P.O. Box 4256
Ithaca, NY 14852-4256

Dear Ms. Warholic:

Re: Withdrawal of Application for Special Local Needs (SLN) Labeling for Sandea™
    Herbicide (EPA Reg. No. 10163-254) Use on Cucumbers

The New York State Department of Environmental Conservation (Department) acknowledges
withdrawal of your application, received May 23, 2001, to register a Special Local Needs
(SLN) label for Sandea™ Herbicide (EPA Reg. No. 10163-254) for use on cucumbers. As
requested in your withdrawal letter, dated August 21, 2001, options for remedying the
reservations for products containing the active ingredient halosulfuron-methyl are
outlined below.

Herbicides with the active ingredient halosulfuron-methyl were originally registered for
use in New York State over the objections of the Bureau of Habitat (BoH) of the Division
of Fish, Wildlife & Marine Resources. The BoH objected to the registration of these herbicides
because of the potential for toxicity to nontarget aquatic plants.

According to the United States Environmental Protection Agency (USEPA) Data Evaluation
Record (DER) of the 14-day toxicity test using Lemna gibba (duckweed), the EC50 for
halosulfuron-methyl was 0.042 μg/L (42 parts per trillion). The no observed effects
concentration was found to be 0.023 μg/L (23 parts per trillion). The BoH normally does
not put much confidence in the USEPA-mandated 14-day Lemna laboratory toxicity test,
because the endpoint for the test is statistically significantly reduced growth compared
to the growth of Lemna in controls. While this test can demonstrate the potential for
reduced growth by exposed plants, it ordinarily does not show that any significant long-term
ecological impacts actually result, or that exposed nontarget plants will not fully recover
and resume normal growth as soon as the exposure is terminated. However, in the case of
halosulfuron-methyl, the USEPA reviewer made the notation under the heading: Other
Significant Results, that: "Abnormal plant division was observed after day 9 in the
0.046, 0.091, 0.18, and 0.37 μg ai/L concentrations. Colony breakup and root destruction
was apparent by day 9 in the 0.18 ug ai/L treatment." That statement suggests that actual
damage beyond simple growth inhibition actually might occur from exposure of aquatic
macrophytes to halosulfuron-methyl.

Besides nontarget aquatic macrophyte toxicity, BoH is also concerned about the persistency
of halosulfuron-methyl. The solubility of halosulfuron-methyl is 1630 mg/l, and the Kow is
46.8. These characteristics indicate that halosulfuron-methyl can persist in solution in
the water column. According to USEPA DERs:

1)  Hydrolysis of halosulfuron-methyl is pH dependent, with a hydrolytic half-life of
    27 days at pH 5, 14 days at pH 7, and 0.75 days at pH 9.

2)  Photolysis of halosulfuron-methyl occurred with an average half-life of 24 days.

3)  The anaerobic metabolic degradation half-life for halosulfuron-methyl was 18-27 days.

4)  Preliminary results of a field study showed that the levels of halosulfuron-methyl
    dropped to < 0.5 ppb and remained at that level for 60 days, when the study was
    apparently terminated. The use of "<" suggests that 0.5 ppb is the detection limit.
    However, the 14-day LC50 for Lemna gibba is 0.042 ppb, which is an order of magnitude
    below the above-stated detection limit.

5)  No data regarding the aerobic metabolic degradation half-life are available.

The BoH is concerned that halosulfuron-methyl is persistent and toxic at labeled rates to
nontarget aquatic macrophytes exposed via runoff. The concerns identified by BoH regarding
the potential for adverse impacts to nontarget aquatic vegetation have never been
satisfactorily addressed. To resolve concerns, an applicant could:

1)  Conduct a microcosm test with halosulfuron-methyl that showed after the compound had
    dissipated from the water, normal growth of exposed aquatic plants resumed; or

2)  Conduct a field surface water monitoring study in areas where halosulfuron-methyl
    is used that examines impacts on growth of aquatic macrophytes as well as the
    dissipation of halosulfuron-methyl in the aquatic environment.

The Department will classify an application to register an additional use of
halosulfuron-methyl as a major change in labeled (MCL) use pattern. Such an
application must include information which addresses the unanswered questions regarding
the potential for adverse impacts to nontarget aquatic vegetation. According to the BoH,
the best possible demonstration of the safety of halosulfuron-methyl is a microcosm test,
as described above.

If you have any questions, please contact me, at (518) 402-8788.


Maureen P. Serafini
Director, Bureau of Pesticides Management
Division of Solid & Hazardous Materials

cc:  J. Bashford, Gowan Company