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Clopyralid - Withdrawl of Application to Register 2/94

New York State Department of Environmental Conservation
50 Wolf Road, Albany, New York 12233
CERTIFIED MAIL                        FEB 01 1994
Mr. Steve A. McMaster
Manager, State Regulatory Affairs
308, 3E
9330 Zionsville Road
Indianapolis, IN  46268-1054
Dear Mr. McMaster:
Re: Applications to Register the following DowElanco Pesticide Products:
     Stinger Herbicide   (EPA Reg. No. 62719-73)
     Transline Herbicide (EPA Reg. No. 62719-73)
     Confront Herbicide (EPA Reg. No. 62719-92)
     Pursuant to your January 10, 1994 correspondence to this office,
the New York State Department of Environmental Conservation acknowledges
DowElanco's decision to withdraw the applications to register the
referenced pesticide products containing the new active ingredient
     The data package submitted by DowElanco on January 17, 1992 to the
New State Department of Environmental Conservation (NYSDEC) for the
referenced products was reviewed by the NYSDEC's Pesticide Product
Registration Section, Division of Water (DOW) and Division of Fish and
Wildlife (DF&W), and by the New York State Department of Health
(NYSDOH). The reviews raised serious concerns about the leaching
behavior of Clopyralid and its potential to impact groundwater. These
concerns, initially expressed in our October 7, 1993 correspondence,
were heightened by the following Environmental Hazards statement on the
product labels which identifies Clopyralid as a leacher and advises
users to avoid application of the referenced products in vulnerable
     "Clopyralid is a chemical which can travel (seep or leach) through
soil and under certain conditions contaminate groundwater which may be
used for irrigation or drinking purposes. Users are advised not to apply
clopyralid where soils have a rapid to very rapid permeability
throughout the profile (such as loamy sand to sand) and the water table
of an underlying aquifer is shallow, or to soils containing sinkholes
over limestone bedrock, severely fractured surfaces, and substrates
which would allow direct introduction into an aquifer. Your local
agricultural agencies can provide further information on the type of
soil in your area and the location of groundwater.~
     Therefore, the Department required DowElanco to provide additional
information, supported by analytical results, to demonstrate that the
use of the referenced products would not impact groundwater quality in
New York State.
     Under the statutory review timeframes in the 1992 pesticide
legislation, the Department registration decisions for the subject
products were due by December 1, 1993. In a submission dated November
23, 1993, DowElanco responded to the Department's concerns expressed in
the October 7, 1993 letter and waived the decision date until February
1, 1994 in order to allow the Department ample time to thoroughly review
the following technical response and three additional studies
accompanying the correspondence:
1. Title:    Response to Issues of New York State Relevant to
             the Registration of Stinger, Transline and Confront
Author:      S.E. Zabik
2. Title:    Dissipation of Clopyralid in Swedish Soils
Dated:       March 1989
Study No.:   GHE-P-2109
3. Title:    Dissipation of Clopyralid from Three Canadian Field Soils
Dated:       November 19, 1991
Study No.:   87069
4. Title:    Behaviour of [2,6-14C] Clopyralid(Lontrel*) in a Sandy
             Pseudogley-Braunerde After Post-Emergence Application to
             Sugar Beet
Dated:       May 1992
Study No.:   GHE-P-2908
     After evaluating the DowElanco November 23, 1993 information, we
continue to have serious concerns about potential impacts from
Clopyralid on groundwater/drinking water resources in New York State.
Overall, the additional field studies shed little light on the
propensity for Clopyralid to leach to groundwater in New York State.
     The studies submitted for our review were performed under
conditions which are not representative of label use directions for the
referenced products and which are not representative of climatic
conditions found in New York State.  Soils in the test plots had low
permeabilities and high organic matter contents, and abnormally dry
weather conditions prevailed at all field study sites during the growing
season.  All studies utilized low application rates intended primarily
for food crop uses.  Maximum label application rates intended for non-
cropland uses and late season or multiple applications were not
considered. Since the Clopyralid products are postemergent herbicides, a
mid-spring application followed by a late summer application is
plausible for New York State.  Despite these limitations, Clopyralid was
measured in soil to a depth of 25 to 50 cm in the Swedish studies and to
a depth of 75 to 90 cm in the Canadian studies, as well as in some
leachate samples.
      Clopyralid dissipated more rapidly in the additional field studies
than indicated by the aerobic soil metabolism and terrestial field
dissipation data submitted previously. As in previous studies, microbial
degradation was the principal dissipation pathway. Laboratory data
previously submitted demonstrated that the rate of microbial degradation
slowed as soil concentrations of Clopyralid were increased. We are
concerned that the application rates used in the additional studies
(120, 240, and 300 g ae/ha) may not accurately predict dissipation rates
when Clopyralid is applied at the maximum rate (560 g ae/ha) allowed on
the Stinger and Transline labels.
     Clopyralid was detected at levels of 0.5 and 6 ug/L on one occasion
in leachate collected from tile drain plots at the Lanna site in Sweden.
This detection was attributed to Clopyralid percolation through
preferential flow paths (macropores) that developed in the clay soil due
to early summer drought. Unfortunately, a tracer was not employed at any
of the study sites to characterize water movement through the soil.
     Using the equation Cw = Ct/tKd+W)/ where Cw is the soil solution
concentration, Ct is the total soil residue concentration, Kd is the
soil/water adsorption coefficient, and w is the gravimetric water
content fraction, DowElanco has estimated Clopyralid concentrations in
pore fluids at the limit of quantitation (LOQ) of field dissipation
studies (Ct= 5ug/kg) and a Kd value of 0.009. This estimate assumes that
leaching occurs only when the concentration of Clopyralid is at the LOQ.
If significant recharge events occur before microbial degradation takes
effect, i.e., within one month of application, it is reasonable to
assume a total soil residue concentration (Ct) of 50 ug/kg or 100 ug/kg
based on an application rate of 560 g ae/ha. The soil solution
concentrations (Cw) for various soil moisture values are calculated in
the following table using the highest reported Kd value (0.12) for
  w (L/kg)                                         Cw  (ug/L)
                              Ct  (ug/kg) = 100         50         5
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
   0.1                                      452        227        23
   0.2                                      312        156        16
   0.3                                      238        119        12
   0.4                                      192         96        10
   0.5                                      161         81         8
     In this case, the concentration of Clopyralid in soil pore water
would be in the range of 8 ug/L to 452 ug/L. The effect of dilution, as
soil pore water enters the saturated zone (groundwater), is calculated
by using the equation Cw (sat) = Cw x DF, where the dilution factor (DF)
= w/0.5 assuming a 50% soil pore space. If maximum dilution is assumed
(DF = 1), the bottom row of values represent the concentration of
Clopyralid in groundwater for total soil residue values of 5, 50, and
100 ug/kg. The calculations show that groundwater concentrations of
Clopyralid may reach 161 ug/L.
     Groundwater simulations were also conducted by this Department
using the LEACHM, and PESTAN models. The PESTAN 4.0 model was used to
simulate the downward movement of Clopyralid (Transline) when applied to
a loamy sand soil at the maximum label rate of 560 g ae/ha. Model
observations were taken at 1, 10, 30, 180, and 360 days post-
application. The soil profile was observed at 12 cm intervals to a depth
of 1.22 m and the recharge rate was 0.003 cm/hr to coincide with the
estimated soil recharge rate for Albany County, New York. The model
estimates the concentration of clopyralid in pore water to be 22 ug/L at
the 1.22 m depth on day 360.
     The LEACHM simulations were conducted from 01/01/65 to 12/31/89 on
sandy soil using Kennedy Airport rainfall data from the same 25-year
period with leachate concentrations measured at a depth of 1100 mm. The
model simulated one annual application of Clopyralid at the maximum
Transline label rate of 56 mg ae/m2. Simulations were performed using
various combinations of Koc (0.4-12.9) and half-life (14-301 days) input
parameters. Estimates show that concentrations of Clopyralid in leachate
may reach peak annual levels of 225 ug/L. The 25-year LEACHM simulations
indicate that the 360-day PESTAN simulation time frame may not be long
enough for Clopyralid to establish a "steady state" leaching pattern.
These estimates raise additional concerns since both modeling efforts
did not consider multiple annual applications.
     The other issue of concern is the enforceability of the groundwater
advisory statement under the Environmental Hazard section of the product
labeling. The Department canvassed Cornell University and the USDA Soil
Conservation Service regarding the availability of information to guide
the user in avoidance of vulnerable sites specified by the advisory
statement. While groundwater vulnerability guidance by soil type and
aquifer location is available to guide users of agronomic pesticides,
there is no integrated mapping available to address such vulnerable
sites as "soils containing sinkholes over limestone bedrock, severely
fractured surfaces, and substrates which would allow direct introduction
into an aquifer."
    Therefore, after reviewing all the information submitted by
DowElanco in support of the registration application for the referenced
pesticide products, the Department has determined that use of the
referenced products in conformance with the label directions could
result in deterioration of groundwater/drinking water resources in New
York State. Clopyralid has high leaching potential and the environmental
fate data does not adaquately define field dissipation and leaching
characteristics. Comprehensive groundwater vulnerability mapping needed
to enforce the Environmental Hazards statement is not available.
     If DowElanco wishes to resubmit an application to register
Clopyralid containing products in New York State, the above- mentioned
issues must be addressed. We suggest you contact Maureen Serafini, of my
staff at (518/457-7446) for protocol guidance prior to initiation of any
new studies aimed at addressing our concerns.
   Please contact Ms. Serafini if you have any questions on this
                                  Norman H. Nosenchuck, P.E.
                                  Division of Hazardous Substances
cc:  N. Kim - Dept. of Health
     D. Rapp - NYS Dept. of Agriculture and Markets
     D. Rutz - Cornell University ~/