Response to Public Comments on EPA's "Memorandum Supporting Proposed Decision to Approve Registration for the New Active Ingredient: Tiafenacil" Docket ID: EPA-HQ-OPP-2019-0413.
This document summarizes the U.S. Environmental Protection Agency (referred hereafter as EPA or the Agency) responses to public comments received through the public notification of the receipt of application for registration of the new active ingredient tiafenacil, and the announcement of the proposed decision to unconditionally register  tiafenacil, under 3(c)(5) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). 
The Agency, as required by FIFRA section 3(c)(4), published in the Federal Register on September 3, 2019 a Notice of Receipt (NOR) of application for registration of tiafenacil, submitted by ISK Biosciences Corporation, and announced a public comment period for 30 days. During the public comment period, EPA received three comments on the receipt of application for the proposed action; however, none of the comments were relevant to the proposed new uses
EPA announced the proposed decision of the unconditional registration of tiafenacil on July 31, 2020 and held a public comment period for 30 days. Nine comments were received during that period, from the United States Department of Agriculture (USDA), the National Cotton Council (NCC), the National Corn Growers Association (NCGA) the American Soybean Association (ASA), the Kansas Corn Growers Association (KCGA), the South Dakota Corn Growers Association (SDCGA), the Center for Biological Diversity (CBD), one individual from North Dakota, and from one anonymous commenter. The Agency's review and responses are summarized in this document.  
1. Comments Received on the Agency's Proposed Decision to Register Tiafenacil
CBD Comment #1 (presented in summary form): Comply with duties under Section 7 of the Endangered Species Act (ESA), including completion of consultation on all synergistic and cumulative uses.
EPA 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.
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 Federally listed threatened and endangered species (collectively, 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 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.
Since that time, EPA has conducted biological evaluations (BEs) on three pilot chemicals representing the first nationwide pesticide consultations (final pilot BEs for chlorpyrifos, malathion, and diazinon were completed in January 2017). These initial pilot consultations were envisioned to be the start of an iterative process. The agencies are continuing to work to improve the consultation process. For example, after receiving input from the Services and USDA on proposed revisions to the pilot interim method and after consideration of public comments received, EPA released an updated Revised Method for National Level Listed Species Biological Evaluations of Conventional Pesticides (i.e., Revised Method)  in March 2020. During the same timeframe, EPA also released draft BEs for carbaryl and methomyl, which were the first to be conducted using the Revised Method. 
Also, a provision in the December 2018 Farm Bill included the establishment of a FIFRA Interagency Working Group to provide recommendations for improving the consultation process required under section 7 of the Endangered Species Act for pesticide registration and Registration Review and to increase opportunities for stakeholder input. This group includes representation from EPA, NMFS, FWS, USDA, and the Council on Environmental Quality (CEQ). Given this new law and that the first nationwide pesticide consultations were envisioned as pilots, the agencies are continuing to work collaboratively as consistent with the congressional intent of this new statutory provision. EPA has been tasked with a lead role in this group, and EPA hosted the first Principals Working Group meeting on June 6, 2019.  
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, the risk assessment for tiafenacil does not include a complete ESA analysis and effects determinations for specific listed species or their designated critical habitat.
With respect to the evaluation of tiafenacil and as explained in the proposed decision, current data indicate that the ecological risks presented by uses of tiafenacil are generally low. To the extent that the EPA receives new information indicating that tiafenacil may pose a greater risk to listed species than indicated by the existing scientific database for this pesticide, the EPA will reevaluate the terms of registration and determine whether use restrictions to protect listed species are necessary.
CBD Comment #2: Require that the registrant provide all necessary data and studies.
EPA Response: The registrant for tiafenacil (ISK Biosciences Corporation) has satisfied all guideline requirements in their submission in support of registration of tiafenacil. The current database is adequate and supports the human health and ecological assessments. No data gaps were identified for tiafenacil.
CBD Comment #3: Incorporate necessary factors (effects on ESA listed species, effects on pollinators and other beneficial insects, endocrine disruption, and cumulative or synergistic effects) into evaluation and any proposed decision.
EPA Response: Effects on ESA listed species is addressed above (see EPA response to CBD comment #1).
Furthermore, the ecological risk assessment conducted in support of the registration of tiafenacil evaluated potential risks to pollinators. In estimating risk to bees associated with the proposed uses of tiafenacil, the Agency followed OPP's published guidance entitled "Guidance for Assessing Pesticide Risks to Bees." This guidance presents an iterative, tiered process for assessing risks that considers multiple lines of evidence related to exposure and effects of pesticides to bees. 
There is no evidence in the available data of endocrine disruption for tiafenacil (all available toxicity data is summarized in the toxicity profile table of the human health risk assessment). Furthermore, EPA prioritizes chemicals undergoing registration review for screening under the Endocrine Disruptor Screening Program. 

Cumulative effects were considered in the human health risk assessment. EPA has not made a common mechanism of toxicity finding as to tiafenacil and any other substances and tiafenacil does not appear to produce a toxic metabolite produced by other substances. 
For EPA's response to comments on synergistic effects, see response to CBD Comment #7 under this section.
CBD Comment #4: Place appropriate restrictions on uses to avoid and minimize adverse effects.
EPA Response: Based on all available data, the Agency has determined that use of this pesticide according to the label directions on the final stamped label will not result in unreasonable adverse effects to human health or the environment. Resistance management language has been incorporated into the precautionary label language to not only help maximize the effectiveness of tools available for growers but to reduce pesticide loading in the environment and non-target exposure to pesticides and to minimize adverse effects. Any restrictions necessary to protect human health and the environment from unreasonable adverse effects are included on the final labels.
CBD Comment #5: The EPA must support any assertion that products with new active ingredients are "safer" or that they will actually replace older pesticide use.
EPA Response: 
The Agency does not permit use of the word "safe" on labels or in labeling. EPA's regulation, in 40 CFR 156.10(a)(5) provides examples of statements that are considered to be misbranded, which includes "claims as to the pesticide, or its ingredients, including statements such as "safe" ... without such a qualifying phrase as "when used as directed." It is the Agency's position that, though some pesticides hold more or less risk than others, none are completely without risk. The word "safe" has potential to lull users into a sense of complacency about taking the appropriate measures to protect themselves and the environment. 
The EPA identified registered alternative herbicides for each individual crop and completed a comparison of the toxicity (i.e., hazard) of tiafenacil. These alternative herbicides include glyphosate for use in corn; glyphosate for use in cotton as an herbicide during preplant or active growth stages; glyphosate, 2,4-D, and dicamba for use in fallow; glyphosate for use in grapes; glyphosate for use in soybeans; 2,4-D, glyphosate, fluroxypyr, and bromoxynil for use in wheat; and paraquat for use in cotton as a desiccant.
In its analysis, the Agency conducted a chemical-by-chemical comparison based on the most recent toxicity data available to the Agency. Generally, tiafenacil is less toxic to aquatic animals, birds and mammals than bromoxynil and paraquat; however, the other alternatives are similar or lower in toxicity. For birds and based on acute oral exposure, tiafenacil is less toxic than 2,4-D, dicamba, bromoxynil and paraquat. Similarly, for mammals, tiafenacil is less toxic than 2,4-D, bromoxynil and paraquat on an acute oral exposure basis; however, as with aquatic animals, the remainder of the alternatives have lower or comparable toxicity to that of tiafenacil. Generally, for both aquatic and terrestrial plants, the identified alternatives have lower or comparable toxicity to that of tiafenacil; however, tiafenacil is less toxic to aquatic nonvascular plants than paraquat. In addition, there will be an overall lower environmental loading with tiafenacil because the application rates are well lower than the alternative herbicides.  The Agency's benefits assessment has not determined tiafenacil to be a replacement to older pesticides but has identified this chemical as an additional weed control and resistance management tool.
CBD Second Comment #6: The EPA must take into account real-world scenarios.
EPA Response: The Agency accounts for real-world scenarios from both ecological and human health perspective. Estimated environmental concentrations are generally conservative where aquatic exposure estimates are based on a reasonably conservative conceptual model of a standard ecological water body that was reviewed by a Scientific Advisory Panel. Monitoring data sometimes detect or report values that are above estimated exposure modeling values used in risk assessment, supporting the environmental relevance of the modeling results. Terrestrial exposure estimates are based on measured pesticide residue data and, therefore, represent real-world exposure values. They also represent high-end values from the distribution such that higher exposure values are expected to be rare. However, misuse or accidental exposures resulting from not following pesticide labels are not specifically assessed.
Additionally, as a part of every human health risk assessment, the Agency considers a large variety of consumer subgroups according to well-established procedures. In line with the Agency policy, risks to population subgroups from pesticide exposures are estimated based on patterns of that subgroup's food and water consumption, and activities in and around the home that involve pesticide use in a residential setting. Extensive data on food consumption patterns are compiled by USDA's National Health and Nutrition Examination Survey, What We Eat in America, (NHANES/WWEIA) and are used in pesticide risk assessments for all registered food uses of a pesticide. These data are analyzed and categorized by subgroups based on age and ethnic group. Moreover, the Agency is able to assess dietary exposure to smaller, specialized subgroups and exposure assessments are performed when conditions or circumstances warrant. Whenever appropriate, non-dietary exposures based on home use of pesticide products and associated risks for adult applicators and for toddlers, youths, and adults entering or playing on treated areas post-application are evaluated.
CBD Comment #7: The EPA must assess the enhanced toxicity of pesticide mixtures.
EPA Response: The EPA has developed an interim process to evaluate effects of mixtures of active ingredients based on patents granted by the U.S. Patent and Trademark Office (U.S. PTO) on the basis of the applicant showing the combined effects of the mixture are synergistic (i.e., the effect of a mixture of pesticides is greater than the sum of the individual effects). To ensure that effects data on the mixture that may be relevant to ecological risk assessments are considered, the EPA requests that registrants of new chemicals submit toxicity data for mixtures that were provided to the U.S. PTO to support patents. The EPA has provided guidance to assist registrants in identifying relevant data for such submissions. In response to the request and guidance ISK Biosciences Corporation completed a search of U.S. patent data to identify any claims of synergy (or greater than additive (GTA) effects) with other currently registered pesticides and these data were submitted to EPA.  EPA's review of these patents did not identify any that met all of the established criteria as described by the Agency's approaches for GTA review. Therefore, the EPA does not have any risk concerns about environmental effects relating to GTA effects of pesticides with tiafenacil at this time.  
Anonymous Comment (presented in summary form): This commenter requested that EPA not approve tiafenical based on concerns that the compound would have "long-term consequences for freshwater organisms and will degrade ecosystems". In support of their request, they cited various elements of the ecological risk assessment regarding potential hazards to fish and invertebrates.  
EPA Response: The Agency appreciates the concerns expressed in the comment. The ecological risk assessment concluded that acute risk for fish and invertebrates and chronic risk for invertebrates are below levels of concern and indicate that likelihood of adverse effects on these taxa from the proposed uses of tiafenacil is low. The assessment indicates that chronic exposure for fish to tiafenacil could result in reduced survival of fish in clear shallow water, based on an adjusted toxicity value for chemicals which are light-dependent peroxidizing herbicides. Ecological risk assessments are intended to be conservative in terms of the toxicity and the exposure values used to estimate risk.
In terms of exposure, modeling for tiafenacil residues in surface water utilized a range of standard and non-standard scenarios representative of vulnerable area where crops are grown to generate Estimated Environmental Concentrations (EECs) protective of potential exposure. Part of this conservatism is to base the assessment on the no-observed-adverse effect concentration rather than a concentration at which effects actually occurred under laboratory conditions. In this case an additional safety factor was applied to account for potential enhanced sensitivity to light. Also, tiafenacil degrades rapidly in the environment; however, to provide a conservative estimate of hazard, the risk assessment assumed that the chemical would remain toxic for a longer period as it degrades and that these exposure levels would remain constant over 60 days. In an estuarine/marine environment though, there are tidal fluxes where exposure is likely to be diluted by influx of water without tiafenacil residues. 
As noted in the ecological risk assessment, while chronic risk estimates exceed levels of concern for fish based on total residues (i.e., parent plus degradates) and an adjusted toxicity value, risk estimates drop below levels of concern when the parent compound alone is considered. The extent to which a sensitive fish would be in shallow, clear water for the protracted period of time modeled in the assessment is uncertain; however, when looking at the parent compound alone (i.e. assuming that the degradates are less toxic than the parent or differ in the mode of action), risk estimates across all of the aquatic animals assessed are below agency levels of concern.
USDA comment: 
The USDA Office of Pest Management Policy (OPMP) commented in favor of the registration of tiafenacil. The USDA strongly supports EPA's proposal to register tiafenacil and expressed confidence that U.S. growers will derive great value from the new active ingredient and its proposed uses. The USDA believes tiafenacil offers a new herbicide that provides equivalent weed control as currently registered herbicide options and will serve as an important resistance-management tool for many growers throughout the United States. OPMP stated that, in light of the high benefits and low risks associated with the proposed uses, they strongly support the proposed registration allowing growers to have access to tiafenacil's additional flexibility as a component in integrated weed management programs and its valuable option to growers resistance management strategies. 
EPA Response: The Agency acknowledges USDA's comment and considered the information as part of the decision to register tiafenacil. 
The National Cotton Council (NCC) comment: NCC commented in favor of the registration of tiafenacil and notes that the new active ingredient will increase weed control program options in cotton and other crops. 
EPA Response: The Agency acknowledges NCC's comment and considered the information as part of the decision to register tiafenacil.
The National Corn Growers Association (NCGA) comment: NCGA expressed support for the registration of tiafenacil. Most notably to NCGA, the new active ingredient has the ability to be tank mixed with a long list of other herbicides approved for corn production. Farmers' ability to tank mix products that target weeds multiple modes of action is another critical component of managing existing and preventing future herbicide resistance. 
EPA Response: The Agency acknowledges NCGA's comment and considered the information as part of the decision to register tiafenacil.
The American Soybean Association (ASA) comment: ASA commented in support of registering tiafenacil. ASA notes that the registration of tiafenacil for preplant and preemergent uses would provide U.S. soybean growers with another meaningful tool to improve yields and operations, control herbicide-resistant weed pressures, and maintain conservation practices.
EPA Response: The Agency acknowledges ASA's comment and considered the information as part of the decision to register tiafenacil.
The Kansas Corn Growers Association (KCGA) comment: KCGA commented in support of the registration of tiafenacil and stressed the importance of tools such as tiafenacil in Kansas where a vast majority of farms utilize reduced and no-till crop management systems. KCGA believes that new tools such as tiafenacil are invaluable for allowing these environmental practices to continue and that if these tools are not available, farmers will be forced to revert to full tillage methods.
EPA Response: The Agency acknowledges KCGA's comment and considered the information as part of the decision to register tiafenacil.
The South Dakota Corn Growers Association (SDCGA) comment: SDCGA commented in favor of the tiafenacil registration and welcomes the new active ingredient's option for early season management of weeds. SDCGA also notes another advantage of tiafenacil being that it can be tank-mixed with many other herbicides that are approved for corn production to target various weed problems.
EPA Response: The Agency acknowledges SDCGA's comment and considered the information as part of the decision to register tiafenacil.
The Individual from North Dakota's comment: This individual voiced their support for the tiafenacil registration, stating that, with broadleaf weed resistance to glyphosate and other herbicides is moving into their region, farm managers are always in need of additional tools to help combat the growing threat of pesticide resistance. This individual believes that federal registration of tiafenacil will provide such support.
EPA Response: The Agency acknowledges the individual from North Dakota's comment and considered the information as part of the decision to register tiafenacil.










