imazethapyr NYS DEC Letter - Application to Register a Major Change in Label 8/00
New York State Department of Environmental Conservation
Division of Solid and Hazardous Materials
Bureau of Pesticides Management, Room 498
Pesticide Product Registration Section
50 Wolf Road, Albany, New York 12233-7257
Phone: (518) 457-7446 o FAX: (518) 485-8990
July 19, 2000
and CERTIFIED MAIL
RETURN RECEIPT REQUEST
Ms. Rebecca Johnston
(Formerly American Cyanamid Company)
P.O. Box 400
Princeton, NJ 08543-0400
Dear Ms. Johnston:
Re: Application to Register a Major Change in Use for Pursuit DG Herbicide, EPA Reg No 241-350,
to Allow Use in IMI Resistant Corn.
This Department has completed review of your application to register the referenced new
pesticide product in New York State. We have determined that use of the product, if
labeled to exclude sale and use on Long Island, New York, will not pose unreasonable
risks to humans or environmental resources of New York State. Therefore, the label
amendment for Pursuit DG, EPA Reg No 241-350, allowing use in field corn (IMI CornŽseed
hybrids only) will be considered acceptable if the above exclusion is incorporated into
The Department conducted toxicological, ecological effects and environmental fate risk
assessments for imazethapyr and the Pursuit DG formulation for use on field corn. Neither
the ecological risk assessment nor the toxicological risk assessment identified any
concerns that would prevent registration. However, the environmental fate risk assessment
did predict unacceptable impacts to groundwater in sandy soils.
Imazethapyr is persistent and mobile according to laboratory environmental fate studies.
Calculations using data from two aerobic metabolism studies gave the half-life as 33-37
months; absorption/desorption studies with aged parent showed the compound to be very
mobile with Kds of 0.46 to 0.82 for four soils, two sandy loams and two silt loams.
Percentages for sand, silt, clay and organic matter did not appear to have an effect
on sorption. Field dissipation studies with Imazethapyr consistently show persistence
regardless of soil type, agriculture practice and climate effects.
Computer Modeling conducted using the LEACHM model on Riverhead soil (typical for Long Island)
using a Koc of 97, a half-life of three years and an application rate of 1.0 oz. ai/acre/year,
the model projected breakthrough in year one, and consistent peaks of 10-11 ppb. However, on
Howard soil (which is more representative of upstate soils) using a K., of 283 with all other
parameters the same as the Riverhead soil, the model projected peaks of 0.5 ppb after about
Imazethapyr, based on its chemical structure, falls under the 50 microgram per liter NEW YORK
STATE drinking water standard for an "unspecified organic contaminant" (10 NYCRR Part 5 -
Public Water Systems). While model projections for the worst case (Long Island) at I0 - 11
ppb do not approach the trigger value of 1/2 of this Standard, or 25 ppb, there is still
concern for use of imazethapyr on Long Island because of its mobility and persistence.
These impacts were identified in earlier reviews for use of Pursuit on soybeans, dry beans
and alfalfa. At the time of those reviews, the Department did not require a statement
prohibiting use on Long Island, NY as a condition of registration. These crops are not
grown on Long Island and, therefore, product was not expected to be found there. However,
with the addition of field corn, it is expected that there would be some limited use on Long
Island. In order to insure that Pursuit does not get sold or used on Long Island, the
following statement will be required: "In New York State - Not for Sale or Use in Nassau or
Suffolk Counties," or "In New York State - Not for Sale or Use on Long Island." This
statement must be in the general information section of the label to apply to all uses.
Once a label is submitted incorporating the above exclusion, it is expected that approval
can be given within a few days.
If you have any questions, you may contact me at (518)457-7446.
Francis X. Hegener
Pesticide Product Registration Section