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dithiopyr (Dimension) NYSDEC Letter - Registration of Major Change in Label 9/99

New York State Department of Environmental Conservation 
Division of Solid & Hazardous Materials
50 Wolf Road, Albany, New York 12233-7250 
Phone 518-457-6934 FAX 518-457-0629

September 13, 1999


Mr. James B. Davis
State Regulatory Affairs Manager
Agricultural Chemicals Registration
and Regulatory Affairs Department 
Rohm & Haas Company
100 Independence Mall West 
Philadelphia, PA 19106-2399

Mr. Sandford R. Simon 
Director Technical Services 
Pursell Industries, Inc. 
P.O. Box 540
Sylacauga, AL 35150

Dear Messrs. Davis and Simon:

Re: Registration of a Major Change in Label for Dithiopyr Contained in the Pesticide Products
    Dimension Turf and Ornamental Herbicide (EPA Reg. No. 707-247); Vigoro Crabgrass Preventer
    plus Fertilizer(EPA Reg. No. 8660-154); and KGRO Premium Crabgrass Preventer plus 
    Fertilizer (EPA Reg. No. 8660-159)

  The New York State Department of Environmental Conservation (NYSDEC) has reviewed your 
application (received May 7, 1998) for the registration of dithiopyr for homeowner 
use on lawns and ornamentals in New York State. Dimension was registered for use on 
turf in New York State, as SLN NY-95-0001, only for application by commercial applicators 
and was not registered for use in Nassau and Suffolk Counties. As a result of this 
registration decision, Dimension will no longer need registration under the Special Local
Need provision of FIFRA.

  Application for use of Dimension has a long history with the NYSDEC. The initial application
for use of Dimension (EPA Reg. No. 524-431) in New York State was made by Monsanto 
Company on September 12, 1991. The data reviewers for the initial application indicated 
concerns about potential impacts on groundwater, particularly in vulnerable areas of the
State. The available laboratory and field studies did not adequately define the leaching 
characteristic of dithiopyr and its metabolites. Modeling results and calculations 
(based on field studies) performed by the New York State Department of Health (NYSDOH) 
indicated that groundwater concentrations of dithiopyr and its metabolites could approach 
or exceed the potential groundwater standard of 25 micrograms per liter (ug/L) for dithiopyr 
and 50 ug/L for each metabolite. The metabolites of dithiopyr were expected to be mobile in 
soils and results of California field dissipation studies supported concerns that soil 
sampling alone could not be used to define the leaching potential of soluble chemicals. 
Concerns about the potential impacts on groundwater were heightened by dithiopyr's relatively 
high toxic potency (demonstrated in chronic animal feeding studies) and the lack of chronic 
toxicity studies for its metabolites. On December 30, 1993, the Department approved a 
conditional restricted use registration for Dimension in New York State that prohibited 
use on Long Island, New York and required that Monsanto conduct an approved field lysimeter

  On September 23, 1994, the United States Environmental Protection Agency (USEPA) approved 
the transfer of Dimension Turf Herbicide from Monsanto Company to Rohm & Haas Company. On
January 23, 1995, the Department registered to Rohm & Haas Company, Dimension Turf Herbicide 
(EPA Reg. No. 707-245) conditionally as SLN NY-95-0001; a "Restricted Use" pesticide excluding
use in Nassau and Suffolk Counties. The maximum permitted application rate was 0.5 lb dithiopyr 
per acre per year. As a condition of this registration, Rohm & Haas Company agreed to conduct
an approved lysimeter study using soils typical for Long Island.

  With your May 7, 1998 application for homeowner use of dithiopyr, the Department received the 
results of this two-year lysimeter study. In your cover letter you stated that this lysimeter
study supported the current 0.5 lb active ingredient per season use rate for dithiopyr and
with multi-year use scenarios over the past 40 years, suggests that there is minimal potential
accumulation or adverse risk.

  However, our reviewers pointed out that the lysimeter study results indicated that dithiopyr
metabolites can leach through soil and be present in leachate at concentrations above NYSDEC
guidance values (50 ug per liter). In some cases it may also be present above the NYSDOH 
drinking water standards for the combined residues (100 gu per liter). Model validation 
activities suggest that model predictions are likely to underestimate potential leachate 
concentrations. Nevertheless, the modeling conducted by your company predicted that 
concentrations of the diacid metabolite would exceed guidance values and be close to the 
drinking water standard.

  A meeting with Rohm & Haas Company, Pesticide Product Registration staff and representatives 
of NYSDOH was held on October 30, 1998 to discuss the modeling results and consider the 
available options for continued use of dithiopyr in New York State. At this meeting, Rohm & 
Haas Company indicated that they were willing to continue the use restrictions on their 
professional Dimension product, which is a "restricted use" dithiopyr product applied at the 
maximum rate of 0.5 lbs per acre per year excluding Nassau and Suffolk Counties. However, 
Rohm & Haas Company would like to provide product to a distributor for a homeowner fertilizer 
mix with a reduced rate of dithiopyr for use throughout New York State, including Long Island. 
Therefore, Rohm & Haas Company requested that the Department evaluate, as part of this 
registration decision, distributor products submitted by Pursell Industries, Inc., Vigoro 
Crabgrass Preventer plus Fertilizer (EPA Reg. No. 8660-154) and KGRO Premium Crabgrass 
Preventer plus Fertilizer (EPA Reg. No. 8660-159) with 0.17 % and 0.11 dithiopyr, respectively, 
for homeowner use at less than 0.25 lbs per acre per year. Rohm & Haas Company stated that the 
reduced use rate is efficacious when applied in the granular form in fertilizer mixes.

  Because the Department still had concerns regarding use of dithiopyr on Long Island due to its 
vulnerable aquifer, Rohm & Haas Company agreed to monitoring by Rohm & Haas Company for 
dithiopyr and its metabolites on Long Island to alleviate concerns regarding impacts from use 
of dithiopyr on these vulnerable soils.

  A computer-simulated modeling exercise submitted by Rohm & Haas Company for the homeowner 
use product used several different application rates (0.2, 0.25, and 0.3 pounds per acre per 
year) and the same meteorological data as that used in the Dimension modeling with the 
modification that combined weekly precipitation and irrigation totaled at least two inches 
during the months of June, July, and August. In this modeling exercise, the modeled peak 
(17.6 ug per liter) and annual median peak (8.5 ug per liter) leachate concentrations for 
total mono- and diacid metabolites at an application rate of 0.25 pounds dithiopyr per acre 
per year are below the NYSDEC guidance value (50 ug per liter, which was set at one-half the 
State drinking water standard) and the NYSDOH drinking water standard for these combined 
residues (100 ug per liter). Whether these modeling results reasonably predict leaching from 
use of the homeowner product is difficult to determine from the data provided. If homeowners 
can be expected to irrigate more frequently at higher rates or over a longer period of the 
year, then the modeling results may not reflect the leaching behavior of the product under 
normal use conditions but result in underestimating peak concentrations to a degree similar 
to that found in the lysimeter study modeling.

  While the registrant's modeling results suggest that expected leachate and groundwater 
concentrations would be below the NYSDEC guidance values of 50 ug per liter, some dithiopyr 
metabolites are likely to be present in groundwater/drinking water. In areas with vulnerable 
aquifers, such as Long Island, it can reasonably be expected that, with use of the homeowner 
product, some dithiopyr metabolites will leach to groundwater.

  On December l, 1998, Rohm & Haas Company requested that NYSDEC delay the registration decision 
on this application to allow time for them to amend their data submission to develop an 
acceptable well water monitoring protocol and to evaluate potential background for dithiopyr 
on Long Island. On December 4, 1998 the Department granted this time extension.

  Rohm & Haas Company also decided to handle Dimension Turf Herbicide liquid formulation 
(EPA Reg. No. 707-245) separately by removing it from the scope of a Special Local Need 
registration at the federal level and resubmission to New York State as a label revision. 
This label will remain "restricted use" and will state "Not for Use in Nassau and Suffolk 
Counties" and specify a maximum application rate not to exceed 0.5 lb dithiopyr per acre per 
year. Use on ornamentals will also be added and will not be considered a Major Change in 
Label by the Department. However, if any additional changes are made additional review will 
be required. This revised label stating "Not for use in Nassau and Suffolk Counties" and "the 
maximum application rate in New York State may not exceed 0.5 lbs per acre per year" was 
accepted by the USEPA on August 6, 1999. New product labels consistent with this EPA-stamped
"Accepted" label were received by the Department on August 18, 1999.

  The homeowner label use pattern and the label directions were similar to those of other 
homeowner use lawn and ornamental pesticides and did not pose an unreasonable risk to users. 
The Department continues to have concerns for the groundwater/drinking water contamination 
potential of products containing dithiopyr. However, these concerns are mitigated for use of 
Pursell Industries, Inc. products as labeled, in New York State given the maximum application 
rate for dithiopyr of not more than 0.25 lbs per acre per year and the groundwater monitoring 
program on Long Island that Rohm & Haas Company will conduct.

  The groundwater monitoring study protocol as submitted intends to sample and analyze water 
from 30 wells in Suffolk County and ten wells in Nassau County twice annually for a minimum 
period of five years. Samples will be collected and analyzed for dithiopyr and its mono- and 
di-acid degradates in compliance with GLP. The Department relayed concerns regarding the 
length of the proposed study because it may take several years for dithiopyr residues to 
reach groundwater and to be detectable. The Department also requested submission of dithiopyr 
sales data in the areas selected for monitoring so as to ensure the collection of meaningful 

  A meeting was held with Rohm & Haas Company, NYSDOH staff and the Pesticide Product 
Registration staff on April 13, 1999 to discuss these remaining issues. At this meeting, 
Rohm & Haas Company agreed to extend the monitoring program based on mutual agreement between 
Rohm & Haas Company and the Department. Extension of the monitoring program will be reevaluated
in five years and will be dependant upon sales and use data, weather data and analytical 
results. Rohm & Haas Company also agreed to supply all available data on the distribution 
and/or sales of dithiopyr on Long Island. Additionally, Rohm & Haas agreed that they and all 
of their distributors would voluntarily remove product from use on Long Island upon 
notification that a significant pattern of groundwater contamination was appearing in the 
test results.

  Data collected will be compared to guidance values of 12.5 ppb for dithiopyr, 25 ppb for each 
metabolite and 50 ppb for the total metabolites. The trigger points for removal of dithiopyr 
products from Long Island will include confirmed, increasing analytical results which 
approach, not exceed, these guidance values; several confirmed scattered data points which 
approach, not exceed, these values and persist; or a single confirmed area of high concentration
which approaches or exceeds these guidance values. Analytical results will be confirmed 
through resampling of the data point and evaluation of the integrity of its well site. 
However, a single exceedence, which is the result of a confirmed spill, will not be 
considered a trigger point. Once a trigger point analysis is confirmed, Rohm & Haas Company 
will immediately implement voluntary withdrawal of all dithiopyr products from Nassau and 
Suffolk Counties in New York State. This agreement was discussed in correspondence from Rohm 
& Haas Company, dated April 26, 1999.

  Therefore, the NYSDEC accepts for general use registration the dithiopyr homeowner use 
products Vigoro Crabgrass Preventer plus Fertilizer (EPA Reg. No. 8660-154) and KGRO 
Premium Crabgrass Preventer plus Fertilizer (EPA Reg. No. 8660-159) with the reduced 
use rate of less than 0.25 lbs dithiopyr per acre per year in New York State. As a condition
of this registration decision for these homeowner use products, Rohm & Haas Company will:

  1.	Conduct the agreed-upon groundwater monitoring program dated April 13,1999 and amended 
        May 25,1999. Collection of background samples for this monitoring program was initiated
        on July 7, 1999. Actual sample collection will begin in March 2000 and continue through
        September 2005. At that time, the monitoring program will be reevaluated based on 
        mutual agreement between Rohm and Haas Company and the NYSDEC. Continuation of the New 
        York State registration for all dithiopyr containing products will be dependent upon 
        monitoring results and the continuation of the groundwater monitoring program should 
        the NYSDEC deem it necessary. 
  2.	Withdraw all use of any dithiopyr containing product registered for use in New York 
        State should any confirmed monitoring hit reach 12.5 ppb for dithiopyr or 25 ppb for 
        a metabolite.
  3.	Maintain a maximum use rate of 0.25 lbs per acre per year of active ingredient for 
        these products.

  The NYSDEC has based this registration decision and classification of products on a thorough
evaluation of application rates. As part of the negotiations for this decision, the NYSDEC
will accept use of dithiopyr on ornamentals for both the homeowner and professional use 
products, while Rohm & Haas Company has added the New York State restrictions to the federal 
label for Dimension Turf Herbicide (EPA Reg. No. 707-245) eliminating the need for a Special 
Local Need Registration in New York State for this product.

  Any deviations from the following for the professional use product, Dimension Turf Herbicide
(EPA Reg. No. 707-245), containing 12.7% dithiopyr or from this negotiated agreement will 
be considered a Major Change in Labeling and require additional review:

  1.	Not for use in Nassau and Suffolk Counties.
  2.	For use by professional applicators only.
  3.	Maximum use rate of not more than 0.5 lbs per acre per year of active ingredient.
  4.	Continue to pursue an educational program informing potential users of 
        the "Not For Use on Long Island" restriction.

  This registration decision reflects the NYSDEC's analysis of the active ingredient 
dithiopyr and its metabolites, not just the application for the fertilizer mix; therefore, 
this decision also extends to all contractual agreements with distributors or formulators. It
will be the responsibility of Rohm & Haas Company to evaluate all customer labels for 
dithiopyr to ascertain compliance with this New York State negotiated registration decision.

  If you have any questions on this matter, please contact Maureen Serafini, Chief of our
Pesticide Product Registration Section, at (518) 457-7446.

  Enclosed for your records are stamped-accepted labels and a Certificate of Registration
for Vigoro Crabgrass Preventer plus Fertilizer (EPA Reg. No. 8660-154) and KGRO Premium
Crabgrass Preventer plus Fertilizer (EPA Reg. No. 8660-159) and a stamped-accepted label and
Certificate of Registration for Dimension Turf and Ornamental Herbicide 
(EPA Reg. No. 707-245).

Stephen Hammond, P.E. 
Division of Solid & Hazardous Materials

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