Document ID: EPA-HQ-OPP-2015-0554-0014
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2016-09-26T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                                             WASHINGTON, DC  20460

                                                      OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

                                                                 	
Thiabendazole: Response to Public Comments on EPA's Notice of Filing and Notice of Receipt for the proposed Tolerances for the use of Thiabendazole in/on Legume Vegetables (succulent or dried) Crop Group 6 and Foliage of Legume Vegetables Crop Group 7 (Docket ID: EPA-HQ-OPP-2015-0554)

Summary
This document summarizes the U.S. Environmental Protection Agency's (the Agency, EPA) responses to public comments received through the public notification of the receipt of the application for new uses of thiabendazole to treat seeds in the legume vegetable crop group 6; and the establishment of tolerance for foliage of legume vegetables crop group 7.  

On September 9, 2015, EPA published a notice of receipt in the Federal Register for Pesticide Product Registration; Application for New Uses. The Notice for the proposed new use announced a public comment period of 30 days; one comment was received on the notice of receipt. 

The comment was submitted by the Center for Food Safety (CFS) with seven attached abstracts consisting of copyright data; and a copy of a USDA letter sent to the docket previously regarding a proposed rule regarding mitigation of exposure to bees from acutely toxic pesticide products that was published in the Federal Register.  The agency's responses and positions are summarized in this document.  The format of these responses is based on CFS's submission format.  CSF commented about several topics including an endangered species assessment, synergy, pollinators, aggregate risk assessment, environmental persistence, risks to various species, treated municipal wastewater being used for irrigation, widespread contamination and a white-nose syndrome and rabies surveillance program.

The Agency recently completed a risk assessment for the new use of legume vegetables, crop group 6.  The end-use label (EPA Reg No. 100-889) retains the existing maximum seed-treatment rates for pea, chickpea, pigeon pea, and lentil (previously registered), while setting a new maximum seed-treatment rate for all cultivars of bean and other minor legume vegetable crops included in the proposed group.  The newly proposed end-use label also retains the limitation of 0.15 lb a.i./A being applied per year.  

Environmental Assessment Response

OPP's ecological risk assessment process is based on EPA's Guidelines for Ecological Risk Assessment (https://www.epa.gov/risk/guidelines-ecological-risk-assessment) and consists of a comprehensive, robust, and peer-reviewed process that considers extensive environmental fate and ecological effects data used to evaluate the potential ecological exposure and impacts of a pesticide in the environment. This risk assessment is conducted to support the overall decision-making for the proposed pesticidal use.  Exposures and potential risks to plant and wildlife species posed by these uses are expected to be comparable or even less than the existing pesticidal uses of thiabendazole.

The Agency's ecological assessment is conservative as it assumes that 100% of the active ingredient comes off the seed and is available for runoff or leaching.  Seed treatment at the maximum annual rate prescribed on the label is expected to result in minimal risk to aquatic organisms and non-target terrestrial plants.  The new seed treatment uses for legumes do not change the conclusion of low risk to all aquatic organisms and to all plants. 
    
While thiabendazole is highly toxic to fish and freshwater and marine/estuarine aquatic invertebrates on an acute basis in laboratory tests, the new uses are expected to result in very little exposure to aquatic organisms.
    
In tier-1 phytotoxicity tests, plants were exposed to an application rate (0.23 lb a.i./A) which is greater than the maximum annual application rate allowed by the end-use product label (0.15 lb a.i./A). At this higher rate, the observed inhibition of emergence and plant growth was less than the 25% concern trigger for all monocot and dicot plants. Results from the TerrPlant model indicate that the risk quotients (RQs) for non-endangered species are well less than 1, and thus less than the level of concern (LOC). 

For threatened and endangered species, the risks are less certain.  Statistically significant effects were observed in some test species in the seedling emergence and the vegetative vigor studies when conducted at rates three times higher than on the proposed label. As the percent inhibition was no greater than 22% with exposure at 0.23 lb a.i./A, and the proposed new seed-treatment uses are expected to result in nontarget plant exposure at no more than 0.075 lb a.i./A, direct adverse effects to nontarget plants at label rates are expected to be negligible. Additional factors that suggest low risk to nontarget plants are:
    
 Seed treatment uses would result in no spray drift, and thus there would be minimal non-target foliar exposure
 Thiabendazole is highly immobile in soil, and therefore off-site movement from planted fields would be minimal
 The widespread use of thiabendazole as a fungicidal seed treatment and lack of plant incidents suggest that it does not have significant phytotoxicity at the application rates used.
    
EPA does not expect the proposed seed treatment uses of thiabendazole to result in effects to nontarget terrestrial plants.

Acute RQs for risk to birds are all less than 0.1, indicating that the acute risk is below the LOC for both listed and unlisted species of birds.  However, the chronic RQ of 1.38 is slightly above the chronic LOC of 1.0, indicating that all crops within these crop groups 6 and 7 pose potential minor chronic risk to birds.  This conclusion of potential chronic risk to birds is uncertain because the available avian reproduction studies only tested up to 400 mg a.i./kg-diet, which is lower than the estimated exposure values for beans. However, this RQ falls within the range of that previously determined for other existing seed treatment uses of thiabendazole.  
    
Because birds serve as a surrogate for reptiles and terrestrial phases of amphibians, the conclusion that the proposed uses of thiabendazole pose risk to birds also apply to terrestrial reptiles and amphibians with terrestrial phases. However, reptiles and amphibians are generally insectivorous or herbivorous, and therefore determining risks to these taxa is less precise.
    
Acute RQs for risk to mammals are less than 0.1 indicating that acute risk is below the LOC for both listed and unlisted species of mammals. Chronic RQs (2.43-5.31), however, exceed the chronic risk LOC (1.0) for all weight classes of mammals. Therefore, all crops within these crop groups 6 and 7 pose potential chronic risk to mammals.  The chronic risk conclusions for mammals are based on studies in which toxic effects were observed and thus both the no observed adverse effect concentration (NOAEC) and the lowest observed adverse effects concentration (LOAEC) values were established. These RQs fall within the range of those previously determined for other existing seed treatment uses of thiabendazole. Additionally, the conclusions of risk to terrestrial wildlife are based on exposure through direct consumption of treated seeds. Exposure would be much less for species that do not consume seeds, or for which seeds comprise only a small portion of their diet. Additionally, after planting treated seeds, they are always buried with top soil which minimizes them as an easy food source for mammals.

The Agency is reviewing each registered pesticide at least every 15 years to determine whether it continues to meet the FIFRA standard for registration.  Thiabendazole is currently undergoing registration review.  Use sites for thiabendazole that will be assessed as part of this review are listed in Table 3 (pages 8-10) of the Preliminary Work Plan.  Use on mushroom, injection into trees and antimicrobial uses in paints and textiles will be assessed. Data gaps are identified in the Data Call In (DCI) ID#GDCI-060101-1453.  The identified data gaps are generic for all current uses for thiabendazole and are not specifically related to the new uses discussed herein. The data gaps that have been identified for thiabendazole can be found in the Thiabendazole DCI, available in the Thiabendazole Registration Review docket available at: https://www.regulations.gov/docket?D=EPA-HQ-OPP-2014-0175 .

The CFS comment also mentioned their concerns for aggregate exposure.  Consistent with FQPA, EPA did conduct a dietary and aggregate risk assessment was conducted by the agency's Health Effects Division (HED).  These assessments included livestock medicinal uses.  Thiabendazole is used medicinally as a chelating agent to bind metals.  In addition, it is administered to treat several helminthes species such as roundworms in livestock and humans.  These medicinal uses of thiabendazole are regulated by FDA.  The dietary risk assessment considered residues incurred in livestock commodities from the use of thiabendazole as an animal drug regulated by FDA.  Under 21 CFR §556.730, tolerances are established at 0.1 ppm for negligible residues of thiabendazole in uncooked edible tissues of cattle, goats, sheep, pheasants and swine, and at 0.05 ppm for negligible residues in milk.  These tolerances are established for the prescribed dosing and intervals of pre-slaughter withdrawal and milk discard specified under 21 CFR §558.600, §520.2380a, §520.2380b and §520.2380c.  

Potential Impacts on Pollinators Response

In 2014, EPA wrote risk assessment guidance for assessing pesticide risks to bees. The assessment described in this guidance relies upon some toxicity data that were not previously required for honey bees. As EPA OPP assesses the ecological risks of currently registered pesticides through the registration review process, EPA has been requiring the new data for pesticides as appropriate. In cases where the full battery of Tier 1 data was not part of an issued Registration Review DCI, the agency will prioritize the chemical based on the chemical's potential for both bee exposure and effects and then make a decision on when another DCI will be issued. The regulations which establish he data requirements for bee testing have not yet been put in place.  However, during this transitional time between the formalization of new data requirements and when data are available, EPA assesses the risks of pesticides to bees based on the available data. For thiabendazole, a DCI was issued which included bee studies.  These required bee studies are listed in the Thiabendazole DCI, available in the Thiabendazole Registration Review docket available at: https://www.regulations.gov/docket?D=EPA-HQ-OPP-2014-0175 .

Risk is based on hazard and exposure, and use of thiabendazole as a seed treatment is not likely to result in contact exposure to non-soil dwelling terrestrial invertebrates, such as honey bees. On an acute basis, thiabendazole is classified as practically nontoxic to the honey bee (LD50 > 34 ug a.i./bee).  

Based on available information, the Agency holds the position that the acute toxicity data available, combined with the relatively minimal pollinator exposure to treated seeds and negligible pesticide systemic uptake from thiabendazole treated seeds supports a determination that the use of this pesticide according to label directions is unlikely to adversely affect pollinator populations.  Further, the approach confirms to the position in the Label Review Manual.  

Regarding synergistic effects, the Agency does not routinely include a separate evaluation of mixtures of active ingredients, rather the focus is on assessment of individual chemicals. Tank mixing is a common practice in agriculture and the most restrictive label limitations and precautions on the label must be followed by the applicator.  If effects data are available for a formulated product for non-target organisms containing more than one active ingredient, they may be used qualitatively or quantitatively in accordance with the agency's Overview Document and the Services' Evaluation Memorandum (USEPA 204; USFWS/NMFS/NOAA 2004).  The end-use label (EPA Reg No. 100-889) associated with this new use action contains thiabendazole only and is for seed treatment only.  

Endangered Species Act Response

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS) (collectively, the Services), and the U.S. Department of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks to listed species from pesticides. The Interim Approaches were developed jointly by the agencies in response to the National Academy of Sciences' (NAS) recommendations and reflect a common approach to risk assessment shared by the agencies as a way of addressing scientific differences between the EPA and the Services. The NAS report outlines recommendations on specific scientific and technical issues related to the development of pesticide risk assessments that EPA and the Services must conduct in connection with their obligations under the Endangered Species Act (ESA) and FIFRA. 
The joint Interim Approaches were released prior to a stakeholder workshop held on November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues Research and Evaluation Group (SFIREG) meetings, and held a stakeholder workshop in April 2014, allowing additional opportunities for stakeholders to comment on the Interim Approaches. As part of a phased, iterative process for developing the Interim Approaches, the agencies will also consider public comments on the Interim Approaches in connection with the development of upcoming Registration Review decisions. The details of the joint Interim Approaches are contained in the white paper "Interim Approaches for National-Level Pesticide Endangered Species Act Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report," dated November 1, 2013. 

Given that the agencies are continuing to develop and work toward implementation of the Interim Approaches to assess the potential risks of pesticides to listed species and their designated critical habitat, risk assessments for thiabendazole do not contain a complete ESA analysis that includes effects determinations for specific listed species or designated critical habitat. As previously stated, thiabendazole is undergoing registration review.  Thiabendazole Registration Review docket is available at: https://www.regulations.gov/docket?D=EPA-HQ-OPP-2014-0175 . In the ecological problem formulation document for thiabendazole, the Agency described the screening-level risk assessment to determine the potential effects of thiabendazole on all taxa of non-target wildlife and plants, which will assume that listed species and their designated critical habitats may be present in the vicinity of the application of thiabendazole.  That screening-level assessment will allow EPA to focus its future evaluations on the types of species where the potential for effects exists once the scientific methods being developed by the agencies have been fully vetted.  While the agencies continue to develop a common method for ESA analysis, the planned screening level risk assessment for the registration review of thiabendazole will describe the level of ESA analysis completed for this particular registration review case.  Once the agencies have fully developed and implemented the scientific methods necessary to complete risk assessments for endangered and threatened (listed) species and their designated critical habitats, these methods will be applied to subsequent analyses for thiabendazole as part of EPA's actions relative to existing chemicals, under the registration review program.