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dimethomorph NYS DEC Letter - Registration of the New Pesticide Product, Acrobat 50WP Fungicide (EPA Reg. No. 241-410) 3/05

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

March 31, 2005


Ms. Judy Fersch
State Registration Specialist
BASF Corporation
P.O. Box 13528
Research Triangle Park, North Carolina 27709-3528

Dear Ms. Fersch:

Re: Registration of the New Pesticide Product, Acrobat 50WP Fungicide (EPA Reg. No. 241-410), Which Contains the New Active Ingredient Dimethomorph

    The Department has reviewed your application, received June 17, 2004, and additional information, received October 4, 2004, to register one new product Acrobat 50WP Fungicide (EPA Reg. No. 241-410) in New York State. The product contains the new active ingredient dimethomorph (chemical code 268800).

    Acrobat 50WP is a wettable powder recommended for disease control in potatoes, tomatoes, fruiting vegetables, leafy vegetables, leafy brassica greens, taro, bulb vegetables, cucurbit vegetables, hops, lettuce and tobacco. Acrobat 50WP was previously registered in New York State during the 2001 and 2002 growing seasons under a Section 18 for cucurbits.

    The maximum application rate is 6.4 ounces of product (0.2 pound dimethomorph) per acre per application with a total maximum of 32 ounces of product (1.0 pound dimethomorph) per acre per season.

    The application was deemed complete for purposes of review on November 22, 2004 and a registration decision is due by April 21, 2005.

    The Department has reviewed the information supplied to date in support of registration of the new product Acrobat 50WP Fungicide (EPA Reg. No. 241-410).

    The New York State Department of Health (DOH) stated that neither the active ingredient dimethomorph nor the formulated Acrobat 50WP product was very acutely toxic to laboratory animals by the oral, dermal or inhalation routes of exposure. In addition, both the active ingredient and formulated product were not very irritating to the eyes or skin (tested on rabbits), nor were they skin sensitizers (tested on guinea pigs).

    In a subchronic feeding study in dogs, dimethomorph caused a decrease in absolute and relative prostate gland weights at a dose of 43 milligrams per kilogram body weight per day (mg/kg/day); the no-observed-effect level (NOEL) was 15 mg/kg/day. In a subchronic feeding study in rats, no effects were observed, even at the highest doses of dimethomorph tested, which were 73 and 82 mg/kg/day for males and females, respectively.

    Dimethomorph caused some toxicity in chronic animal feeding studies. In a one-year dog feeding study, a decrease in prostate gland weights was observed at a dose of 44.6 mg/kg/day; the NOEL was 14.7 mg/kg/day. In a chronic feeding/oncogenicity study in rats, lesions of the liver and blood vessels, and decreased body weights were observed at 94.6 and 46.3 mg/kg/day for male and female animals, respectively. The respective NOELs were 33.9 and 11.3 mg/kg/day. In a chronic feeding/oncogenicity study in mice, dimethomorph caused decreased body weight gain in males at a dose of 1,000 mg/kg/day with a NOEL of 100 mg/kg/day. No effects were reported in females, at a dose of 1,000 mg/kg/day, which was the highest dose tested. The United States Environmental Protection Agency (USEPA) Office of Pesticide Programs calculated an oral reference dose (RfD) for dimethomorph of 0.1 mg/kg/day based on the NOEL of 11.3 mg/kg/day in the chronic feeding/oncogenicity study in rats and an uncertainty factor of 100. This RfD value has not yet been adopted by the USEPA Integrated Risk Information System (IRIS).

    Dimethomorph caused some developmental toxicity in the offspring of pregnant rats, but not pregnant rabbits, administered this chemical during organogenesis at doses that also caused maternal toxicity. In rats, an increased incidence of fetal post-implantation loss was reported at a maternal dose of 160 mg/kg/day; the NOEL was 60 mg/kg/day. Maternal toxicity (decreased body weight, body weight gain and food consumption) was reported at 160 mg/kg/day with a NOEL of 60 mg/kg/day. In rabbits, no developmental toxicity was reported at the highest dose tested (650 mg/kg/day). Maternal animals showed a decrease in body weights and body weight gains at this dose of 650 mg/kg/day; the NOEL was 300 mg/kg/day. In a rat multi-generation reproduction study, a delay in tooth development in rat pups was reported at doses of 69 and 79.3 mg/kg/day for males and females, respectively. The respective NOELs were 20.8 and 24 mg/kg/day. Parental toxicity, characterized by a decrease in body weights and body weight gains occurred at the same doses (69 and 79.3 mg/kg/day) as reported for the above noted developmental effects in this multi-generation reproduction study. The respective NOELs were 20.8 and 24 mg/kg/day.

    Dimethomorph did not cause oncogenic effects in either rat or mouse chronic feeding studies. This chemical also gave negative results in several genotoxicity studies. Based on the lack of evidence for carcinogenicity in rats and mice, the USEPA classified dimethomorph as "not likely to be a human carcinogen."

    The USEPA established tolerances for dimethomorph residues in or on leafy Brassica greens at 20 parts per million (ppm); fruiting vegetables (1.5 ppm); lettuce (10 ppm); hops (60 ppm); bulb vegetables (2.0 ppm); cucurbit vegetables (0.5 ppm); tomatoes (0.5 ppm); potatoes (0.05 ppm); taro leaves (6.0 ppm); and taro corm (0.5 ppm). The chronic population adjusted dose (cPAD) for dimethomorph is 0.1 mg/kg/day and has the same basis as the RfD. The USEPA estimated that chronic dietary exposure to dimethomorph would be seven percent of the cPAD for the general U.S. population, 0.8 percent for all infants less than one year old and 16 percent for children one to two years old. This chronic exposure analysis is based on the conservative assumptions that 100 percent of the crops are treated and contain tolerance level residues of dimethomorph.

    The USEPA conducted a risk assessment for short- and intermediate-term combined dermal and inhalation exposures of workers to dimethomorph. For mixers/loaders/applicators, the combined margins of exposure (MOE) for short-term dermal and inhalation exposures ranged from 1,200 to 190,000. For intermediate-term dermal and inhalation exposures, the combined MOEs ranged from 290 to 47,000. The USEPA used a dermal absorption factor of five percent and assumed 100 percent absorption for inhalation exposure. For these exposures, it was assumed that workers for ground applications wore a single layer of clothing and gloves (the Acrobat label requires long-sleeved shirt, long pants, shoes plus socks and chemical-resistant gloves). For aerial applicators it was assumed that these workers did not wear gloves. The NOEL used for estimating the short-term dermal and inhalation MOEs was 60 mg/kg/day from the rat developmental toxicity study for maternal effects (decreased body weight, body weight gain and food consumption). For the intermediate-term dermal and inhalation MOEs, the NOEL used was 15 mg/kg/day from the subchronic dog feeding study in which the toxicity endpoint was a decrease in absolute and relative prostate gland weights. Generally, the USEPA considers MOEs of 100-fold or greater to provide adequate worker protection. For post-application exposures of workers involved in field maintenance, the MOEs ranged from 5,800 to 23,000.

    There are no chemical-specific federal or State drinking water/groundwater standards for dimethomorph. Based on its chemical structure, dimethomorph falls under the 50 microgram per liter New York State drinking water standard for "unspecified organic contaminants" (10 NYCRR Part 5, Public Water Systems).

The available information on dimethomorph and Acrobat 50WP Fungicide indicates that neither the active ingredient nor the formulated product is very acutely toxic in laboratory animal studies. Furthermore, dimethomorph was not carcinogenic in rats or mice. Although data from subchronic, chronic and developmental/reproductive studies showed that this chemical has the potential to cause some toxicity, the estimated risks to workers from use of Acrobat 50WP Fungicide are within the range that is generally considered acceptable. In addition, dietary exposure of the general public to dimethomorph on currently labeled crops is not expected to pose significant health risks. Given the above, the DOH does not object to the registration of Acrobat 50WP Fungicide in New York State.

    The Department's Division of Fish, Wildlife & Marine Resources' Bureau of Habitat (BOH) stated that the primary route of dimethomorph environmental dissipation will be via microbial metabolism. Overall the environmental fate section of the data package is weak. The submitted anaerobic soil, aerobic aquatic and anaerobic aquatic metabolism studies are all classified as supplemental. No acceptable terrestrial field dissipation studies have been conducted. Highly conservative assumptions were used in exposure modeling to compensate for the poor fate data quality.

    Dimethomorph is practically nontoxic to birds and mammals on an acute basis but can cause chronic mammalian toxicity at food-item residue levels slightly higher than the highest levels predicted by BOH exposure modeling. It is moderately toxic to aquatic test species.

Post-application runoff modeling using highly conservative screening assumptions indicates there may be potential for chronic fish toxicity to occur in waters adjacent to Acrobat use areas. When degradation rates for fate pathways are minimized and the highest application rate is applied in the shortest allowed time interval, the Rainbow Trout Early Life Stage study Lowest Observable Effect Concentration (LOEC) threshold is exceeded in the shallowest modeled depth following the fourth application.

    The submitted aerobic and anaerobic aquatic metabolism studies were both classified as supplemental by USEPA reviewers due to an unexplained, large (2 orders of magnitude) increase in biomass within the incubation vessels, and incomplete descriptions of test conditions. The increase in biomass may have been responsible for the observed uncharacteristically rapid dimethomorph metabolism. Both studies yielded a dimethomorph half-life (T1/2) of less than one day which is inconsistent with aerobic soil metabolism study results. Aquatic metabolism T1/2s are generally shorter than those in soil but do not typically differ to the degree seen in this case. When the current studies are repaired with submission of additional data, or new studies are conducted, the T1/2s will probably be revised upward. While the rate of aquatic degradation is ill-defined, dimethomorph does in fact degrade and will have a relatively short water column T1/2 making chronic exposures unlikely.

    The BOH stated that when used according to its label Acrobat 50WP Fungicide should not adversely impact fish or wildlife resources.

    The Department's groundwater staff stated that dimethomorph has a solubility of 17 mg/liter and is stable to hydrolysis at pH 4,7 and 9. Dimethomorph had an aqueous photolysis half-life of 50-56 days in a pH 5 sterile aqueous solution and a soil photolysis half-life of 150 days. The aerobic soil metabolism half-life was 117 days in a silty clay loam with 1.6% organic content and a pH of 5.8. Dimethomorph was shown to be of moderate mobility in three standard German soils with kocs of 566, 402 and 290 in sand, humus sand and sandy loam soils, respectively. In a second study of four German soils, kocs were 469, 319, 330 and 274 in silt loam, loam, sand and sandy loam, respectively. In a study with U.S. soils, Kocs were 787 in a sandy loam, and 1588 in a sandy clay loam.

    Modeling was done on Riverhead sand, using an application rate of 1.0 lb. active ingredient per acre per year, a Koc of 290 and an aerobic half-life of 117 days. The model projected peaks starting in the first year and ranging between 0.2 and 0.5 ppb.

    Based on the Koc, application rate, half-life and modeling results, the Department's groundwater staff stated that they have no objection to the registration of Acrobat 50WP Fungicide.

    The Department concludes that Acrobat 50WP Fungicide should not have an adverse effect on the health of workers or the general public, the fish and wildlife resources, or the ground and surface water of New York State when used as labeled.

    Therefore, the Department hereby accepts for registration the new product Acrobat 50WP Fungicide (EPA Reg. No. 241-410).

    The Certificate of Pesticide Registration and a copy of the New York State stamped "ACCEPTED" labeling for Acrobat 50WP Fungicide are enclosed for your records.

    BASF Corporation is reminded that if New York State registration is requested for this product or for any other product which contains dimethomorph with an increased application rate and/or expanded use sites, the product will be considered a Major Change in Labeling and the Department will require an extensive review.

    If you have any questions, please contact Samuel Jackling, Chief of our Pesticide Product Registration Section, at (518) 402-8768.


Maureen P. Serafini
Bureau of Pesticides Management

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