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zinc pyrithione
NYS DEC Letter - Denial of Registration Application 9/03

New York State Department of Environmental Conservation
Division of Solid and Hazardous Materials
Bureau of Pesticides Management, 9th Floor
625 Broadway, Albany, New York 12233-7254
Phone: (518) 402-8788     FAX: (518) 402-9024
Website: www.dec.state.ny.us

September 15, 2003

CERTIFIED MAIL
RETURN RECEIPT REQUESTED

Mr. Myles Alex Walsh
President
E Paint Company
25 Research Road
East Falmouth, Massachusetts 02536

Dear Mr. Walsh:

Re: Denial of Application to Register E Paint ZO (EPA Reg. No. 64684-4) and EP 2000 (EPA Reg. No. 64684-6), Both Contain the Active Ingredient Zinc Pyrithione (Zinc Omadine)

    The New York State Department of Environmental Conservation (Department) has completed its technical review of the product applications and data packages received from the initial application submittal (received on 07/11/00) and data package (received on 10/31/00) as well as the second data package (received on 03/14/01) resubmission of the application on 05/15/02, additional data package (Australian Review of zinc omadine) submitted by Arch Chemicals on 08/29/02 and additional data submitted by the applicant on 09/10/02. The information received was deemed complete for purposes of technical review per Department letter dated 11/18/02. A technical review was conducted during which time certain issues of concern to the Department were addressed in a letter to the applicant dated 03/14/03. As detailed in the following history of the products review, the applicant attempted to respond to the Department's issues of concern. Although the concerns with regard to human health were resolved, the modeling of the amount of active ingredient released into the water column (release rate factor) cont nu es to be unacceptable for the protection of aquatic species. Therefore, the application for the registration of these two products has been denied.

    In response to the Department's letter dated 3/14/03, the applicant requested a 90-day extension of the original registration decision date of 04/17/03 in order to respond to the Department's concerns. Arch Chemicals submitted one document, "Aquatic Fate and Toxic Effects of Zinc Omadine and Copper Omadine - Review and Preliminary Risk Assessment of Use in Antifouling Paints" (dated 12/2/02) on 04/08/03, in response to concerns raised by the Department's nontarget organism review. A registration decision date of 07/16/03 was scheduled. Again, the applicant requested an extension (60 days) of the registration decision date in order to address human health concerns raised by the New York State Department of Health human health review of these products. A second document was submitted by International Coatings Limited, at the request of Arch Chemicals. The submitted document entitled, "The In Vitro Percutaneous Absorption of Radiolabelled Zinc Pyrithione in Two Antifouling Paint Test Preparations through Human Skin" was received on 07/22/03.

    The Department has reviewed the additional information submitted in support of the E Paint Company's application to register the pesticide products EP 2000 (EPA Reg. No. 64684-6) and E Paint ZO (EPA Reg. No. 64684-4) in New York State. EP 2000 and E Paint ZO contain the active ingredient zinc pyrithione (zinc-2-pyridinethiol-l-oxide). These two products are anti-fouling paints intended for use on commercial and recreational watercraft. The Department has reviewed the intended use of EP 2000 and E Paint ZO on boat surfaces as a major change in labeled use pattern (MCL) for zinc pyrithione (zinc omadine) in New York State. Pursuant to the review time frame specified in ECL §33-0704.2, a registration decision date of September 15, 2003 was established. The Department conducted the following technical reviews with regard to the registrations of EP 2000 and E Paint ZO for impacts to human health, nontarget organisms, and the environment. Review summaries are provided below:

Nontarget Organism Review. Issues- Referenced in March 14, 2003 Letter to Applicant:

    The Department has repeatedly requested a complete data package regarding environmental exposure, for these products. However, to date, no results or United States Environmental Protection Agency (USEPA) evaluations of the work in question have been submitted. The Department has determined that zinc omadine readily adsorbs to sediments and modeling has determined that zinc omadine concentrations will build over time. Without the additional studies, the Department is left with a modeling scenario that implies a significant toxicity to nontarget organisms in marine and fresh water environments.

    A second point of concern for the Department is the lack of an adequate description of the material balance in the aquatic fate studies. The 1998 USEPA comparative assessment makes a footnote reference to zinc omadine's 2-pyridinethiol-l-oxide moiety's being a "bidentate ligand" that has the capacity to complex with metals other than zinc like copper, iron, mercury, silver, etc. The materials submitted contain very limited data on this point. However, in the Australian summary document, it is suggested that copper omadine toxicity is similar to zinc omadine toxicity. The degree to which the omadine moiety recomplexes with other metals under field conditions needs to be addressed. Again, with only the submitted materials to work with, zinc omadine, as an active ingredient in anti-fouling paint products, poses a significant risk to nontarget aquatic organisms.

Review of Additional Materials Submitted in Support of E Paint ZO and EP 2000 Antifouling Boat Paints:

    The Division of Fish and Wildlife Bureau of Habitat (BoH) completed an assessment of E Paint ZO and EP 2000 and objected to their registration, per the Department's 3/14/03 letter, due to predicted toxicity to aquatic nontarget organisms. Multiple data requests made to E Paint, Inc., over an extended period of time resulted in a marginally sufficient information base from which to conduct the assessment. That review clearly stated that major uncertainties remained due to the poor quality of the supporting submissions. In response to the initial BoH review, the producer of the active ingredient (ai) zinc omadine, Arch Chemicals, Inc., submitted a review and preliminary risk assessment dated December 2002, and a rebuttal of the BoH assessment. BoH reviewers depend on USEPA Data Evaluation Records (DERs) to establish the scientific validity of industry-conducted research studies, and their adherence to USEPA study guidelines. Also acceptable, are peer-reviewed published works.

    The rebuttal authors identify five points in the marina scenario modeled by BoH they feel are incorrect: 1) the release rate of ai from painted surfaces, 2) decomposition of ai by photolysis not considered, 3) transport of ai out of the marina via water exchange was not calculated, 4) an incorrect assumption regarding transport of ai to sediments was made, 5) the water in the marina was unusually shallow. They address each point presenting data or methods that support their position. They then present modeling results that indicate that these products present minimal risk to aquatic organisms.

    The suggested modifications for the latter four points seem reasonable, though they depend on and/or cite a number of studies not seen by BoH. The first point, the release rate of ai from painted surfaces, is more critical and remains as a primary point of contention.

    The Arch authors state that, "It is widely recognized that release rates obtained in the laboratory using methodology based on the ASTM D5108-90 method should not be used for the estimation of environmental PEC (Predicted Environmental Concentration)." Later, they write, "As stated by the USEPA and the CEPS (the European Paint Makers Association) Antifouling Working Group, laboratory tests based on the ASTM method are useful only for comparing relative release rates from different paints...." The USEPA document they cite is a 1987 Tributyltin (TBT) Technical Support Document. The statement regarding the ASTM method attributed to that document is inconsistent with subsequent USEPA use of leach rate values generated by that method. The USEPA October 1998 Comparative Risk Assessment for TBT and its alternatives in Antifoulant Paints contains PECs for TBT and Zinc Omadine generated using the Luttik-Johnson Model, a European model developed to predict the emission of antifoulants in aquatic environments. In that modeling exercise, the USEPA used a leaching rate determined by the ASTM method. In the September 1999 USEPA Zinc Omadine: Reevaluation and Update RE: Human and Environmental Exposures, Risks, and Data Requirements, USEPA reviewers in the Risk Assessment and Science Support Branch (RASSB), Antimicrobials Division, state that, "The risk conclusions reached previously in RASSB's 10/05/98 review for aquatic animal species have not changed." Those conclusions include acute risks to freshwater vertebrates and freshwater and estuarine/marine invertebrates, and chronic risks to freshwater and estuarine/marine fish and invertebrates.

    The leach rate used in the BoH assessment was determined by the ASTM method and is specific to the paints being evaluated. The rate used in the Arch modeling is an estimate calculated using "a simplified generic model of biocide release." The Arch leach rate value is roughly 30% and 18% o of those used by BoH and USEPA reviewers respectively.

    Recently, through direct contact with USEPA staff, BoH acquired all outstanding Ecological Effects (toxicity) study results submitted to and reviewed by USEPA for which DERs are available. The freshwater and marine invertebrate whole sediment acute toxicity study requirements remain unfulfilled and are listed as such on the new time-limited federal registrations issued 3/17/03. Also listed, are newly imposed requirements including a marine diatom toxicity test, a rice seedling emergence study, and a rice vegetative vigor study. Except for a microcosm study currently under review (cited in the Arch rebuttal document) USEPA staff was not aware of any recent environmental fate study submissions. In their rebuttal document, the Arch authors refer to supplemental aerobic and anaerobic aquatic metabolism studies that were submitted after the aerobic study BoH has results for. Additional studies are referred to or cited but were not submitted to the Department: a seawater die away study, zinc and copper photolysis in pond water and numerous others.

    The ai leaching rate issue needs to be resolved. Arch needs to provide documentation that the ASTM leach rate method produces results inconsistent with the leach rates that occur during actual labeled use conditions.

    The Department is aware that the Zinc Omadine Reregistration Eligibility Decision document (RED), in which all relevant valid study results should be included, is on the 2003 USEPA Office of Pesticide Programs work schedule, but is not progressing at this point as efforts are focused on wood preservatives. A draft version of the RED will be sent to Arch for comment, at which point their December 2002 risk assessment that was submitted to BoH, or a revision, will likely be submitted to USEPA. The leach rate issue, among others, will be debated arid, at some point thereafter, resolved. Until such time as the active ingredient leaching rate estimate can be resolved, the Department cannot support registration of these products for use in marine environments in New York State.

Human Health Review:

    In our letter dated 03/14/03, we indicated that there were several aspects of the USEPA occupational risk assessment for these products that are either problematic or create uncertainty. We also indicated that we would be willing to review any additional toxicological and occupational risk assessment information that the registrant submitted in support of registering these two products. Specifically, we suggested that the registrant submit a revised occupational risk assessment that considers developmental toxicity endpoints, the use of personal protection equipment (PPE), and actual use patterns for these products.

    Additional information was submitted and two occupational risk assessments were included. One assessment was conducted by the United Kingdom's (U.K.) Health and Safety Executive Committee (HSE); the other assessment was performed by Arch Chemicals, Inc. The HSE assessment is based on a number of different shipyard investigations in the U.K. and evaluates exposures to workers performing various tasks associated with applying anti-fouling paints. The assessment assumed that workers weighed 60 kilograms and wore personal protective clothing including gloves and respirators. Exposures were calculated for both a four percent and a one percent clothing penetration factor, and a dermal absorption factor of one percent was assumed. Workers operating the spray apparatus had the highest exposure among the various workers involved in the application of anti-fouling paints. Combined dermal and inhalation exposures for sprayers were 0.006 and 0.04 milligrams per kilogram body weight per day (mg/kg/day) for average and worst-case exposures, respectively, for the four percent clothing penetration scenario. For the one percent clothing penetration scenario, combined exposures of sprayers were 0,002 and 0.02 mg/kg/day, respectively for average and worst-case situations. When these exposure estimates are compared to the no-observed-effect level (NOEL) of 0.5 mg/kg/day from an oral rabbit developmental toxicity study, margins of exposure (MOEs) ranging from about 12 to 250 can be calculated. Generally, the USEPA considers MOEs of 100-fold or greater to provide adequate worker protection.

    The occupational risk assessment prepared by Arch Chemicals, Inc., is based on measurements made of shipyard workers in Singapore. This risk assessment, like the HSE risk assessment, assumed a one percent dermal absorption factor. However, unlike the HSE risk assessment, the Arch assessment assumed a clothing penetration factor of ten percent and involved worker exposure to copper pyrithione, rather than zinc pyrithione. The Arch assessment also did not quantify inhalation exposures, though they did provide measured air concentrations of copper pynthione from spray operations. Overall, this assessment calculated a worst-case worker exposure estimate to be 0.0000063 mg/kg/day for a 70 kilogram worker. Comparing this estimate to the NOEL of 0.5 mg/kg/day, an MOE of about 80,000 can be calculated.

    The registrant also submitted the results of a study on the in vitro penetration of zinc pyrithione from paint residues through human skin. This study demonstrated that about 0.13 percent of the applied zinc pyrithione was absorbed by the skin over a 24-hour period, with about 0.08 percent of this chemical penetrating to the assay receptor fluid. The zinc pyrithione in the receptor fluid represents the material that is available for systemic circulation. Because the risk assessments assumed a dermal absorption/penetration value of one percent, the absorbed dose estimates should be adjusted to account for the measured value of 0.08 percent. So, modifying the exposure estimates from the HSE assessment results in MOEs ranging from 77 to 960. The MOE from the Arch assessment would then become 1,000,000. Of these worker exposure scenarios, the only MOE that is less than the 100-fold or above level generally considered to be acceptable by the USEPA is the HSE estimate for worst-case sprayers with a clothing penetration factor of four.

    The HSE assessment contains several assumptions that should be considered when evaluating the MOEs that were calculated for workers. In the HSE assessment, all zinc pyrithione that was inhaled was assumed to be absorbed. Because these products are paints (and would be a viscous liquid), it may not be valid to assume that all of the inhaled active ingredient will be absorbed from the paint droplets, even if the droplets were small enough to be respirable. Also, zinc pyrithione has a low vapor pressure (2.0 x 10-6 mm Hg), indicating that it is not volatile. Consequently, direct inhalation and absorption of vapor-phase zinc pyrithione from air is expected to be minimal under the conditions that these products would be used, particularly when these applications take place outdoors in a shipyard or marina. The Arch assessment presents measured air concentrations of copper pyrithione that range from less than 0.0003 to 0.041 mg/m3 for personal airspace monitoring. The HSE assessment assumed zinc pyrithione air concentrations of 0.24 mg/m3 or 2.6 mg/m3 for median and worst-case exposures, respectively. Assuming equivalency between these two pynthione compounds, the air levels assumed in the HSE assessment were considerably greater than those measured in the study that forms the basis of the Arch assessment. For the above reasons, the estimates of inhalation exposure may be conservative in the HSE assessment as may be the MOEs that were calculated. Given the information presented in the risk assessments, the dermal absorption data, the chemical-physical properties of zinc pyrithione, and the application practices for anti-fouling paints, we do not expect that the use of the E Paint products will pose significant risks to workers who comply with the labeled PPE requirements. Consequently, all issues regarding human health have been adequately addressed. There is no further need to review these product formulations and use pattern for impact to human health.

Groundwater Review:

    E Paint ZO contains 4.7% zinc omadine and the equivalent of 30.8% metallic zinc. EP2000 contains 4.8% zinc omadine and 28.9% metallic zinc. The inerts do not appear to be solvent carriers. No DERs were submitted; however, a July 8, 1998 USEPA Environmental Fate Science Review memorandum was submitted. This memorandum indicates that the registrant had satisfied all environmental fate data requirements with the exception of the anaerobic aquatic sediment metabolism. The following studies were submitted to the USEPA and found to be acceptable: hydrolysis, aqueous photolysis, aerobic aquatic metabiolism, and adsorption/desorption.

    USEPA indicated that, in general, it appears that zinc omadine is not likely to persist and accumulate in the water phase. Since zinc omadine has a high adsorption coefficient to sediments and low desorption, it is likely to be adsorbed to sediments. Trans metallation (with metals present in the sediment) to form complexes, such as copper omadine, of even higher adsorption coefficient are likely to reduce the aqueous availability even further.

    Zinc omadine should degrade rapidly (half-life of 15 days) in sediments under aerobic conditions as demonstrated by the aerobic aquatic metabolism study. In the aerobic metabolism study, only 6.6% of the zinc omadine was found in the water on day 0 due to trans metallation and adsorption to the sediment. Zinc omadine photodegrades rapidly when exposed to sunlight. Degradation under aerobic conditions resulted in 14 products of which omadine disulfide was clearly the major metabolite. Further oxidation led to sulfur oxidation products in the fresh water, leading to the formation of 11.9% carbon dioxide after 30 days. Mineralization was essentially nonexistent in the salt water experiment.

    In the absence of a good anaerobic aquatic metabolism study, it is difficult to assess the stability of zinc omadine when adsorbed to sediments at high depths where sunlight penetration and oxygen are lacking.

    Also submitted, was an October 2001 Australian review of zinc pyrithione in the product International Intersmooth 360 Ecoloflex Antifouling Paint. Australia reviewed information on the active ingredient. According to this document, hydrolysis was slight in sterile buffers with half-lives of 96-123 days. Two degradates exceeded ten percent, pyrithione disulfide and pyrithione sulfinic acid. The aqueous photolysis half-life was very rapid at 13-18 minutes. Degradates greater than ten percent included pyridine sulfinic acid, pyridine sulfonic acid, pyridine disulfide and pyridine/pyrithione mixed disulfide. Batch equilibrium studies on two soils and two sediments indicated Kocs of 780-2350 in soils and 3600-10600 in the sediments. Desorption values ranged from 870-3290 and 6520-21800, respectively. Australia concluded that much of the zinc pyrithione released to the environment was likely to degrade in the water column before reaching the sediment.

    The registrant also submitted an Evaluation Report from the State of California dated September 21, 2001. Most of the information was in agreement with that presented above in the Australian review. However, California felt that the second phase of the biphasic aerobic aquatic metabolism was 19 days, and they could not determine the first phase timing. California also felt that the aqueous photolysis degradates pyridine sulfinic acid and pyridine sulfonic acid were present in excess of 70% of the applied over the life of the study. They felt that these degradates should be evaluated in the aquatic environment.

    Given that this product is painted onto water craft its labeled use and method of application indicate that it will not be available to impact groundwater resources in New York State.

Summary:

    It is the Department's understanding that the basic registrant (Arch Chemical) is continuing to work with USEPA to resolve the active ingredient release factor model with respect to the marine environment. At the point where this issue is suitably resolved, the applicant may submit a new MCL application for a limited nontarget organism review, in order to register your products in New York State. As the Department is required to operate under legislatively mandated time frames, failure to resolve this outstanding issue by the deadline has resulted in termination of the review process.

    You are reminded that the application fee is nonrefundable. If you wish to reapply, you must submit a complete new application for registration with all required documents and new application fee to register the above-mentioned products.


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