By Timothy D. Backstrom and James V. Aidala
On December 18, 2019, the Office of Pesticide Programs (OPP) of the U.S. Environmental Protection Agency (EPA) issued for comment a Proposed Interim Decision (PID) in the ongoing registration review process for each of the three registered triazine herbicides: atrazine, propazine, and simazine. EPA will allow 60 days for comment on each of these triazine PIDs, but the specific comment deadline will only be established after EPA has published notice concerning the proposed interim decisions in the Federal Register. EPA can utilize an “interim registration review decision” under 40 C.F.R. Section 155.56 whenever it is not yet ready to complete the registration review process, but EPA has nonetheless completed sufficient review to determine that new or interim risk mitigation measures are needed or that additional data or information should be submitted to complete the review. For each of the three triazine herbicides, EPA is proposing to impose specific risk mitigation measures for particular registered uses to mitigate potential health and environmental risks. For each triazine herbicide, EPA is not yet ready to make a final registration review decision because EPA has not made findings in the Endocrine Disruptor Screening Program (EDSP) or an effects determination under the Endangered Species Act (ESA). Several key factors that will affect the final registration review decision for each of the triazine herbicides are discussed below.
Common Factors for Triazine Risk Assessment
There are several common factors to consider with regard to the triazines risk assessment. These include:
- Atrazine, propazine, and simazine are all included in the chlorotriazine chemical class. EPA has determined that these three herbicides, along with three specific chlorinated metabolites, share a common mechanism of toxicity, so human health risks from all of these substances are being assessed by EPA together through one cumulative triazine risk assessment. The contribution of each product to aggregate human risk differs because of somewhat dissimilar use patterns. The combining of risks resulting from use of each triazine means, however, that it may be necessary for EPA to coordinate the ultimate registration review decisions for the three active ingredients.
- As part of the ecological risk assessment for each triazine herbicide, EPA plans to make an effects determination for potentially vulnerable species under the ESA, which in turn will determine whether it is necessary for EPA to consult with the Fish and Wildlife Service or the National Marine Fisheries Service (the Services) concerning potential impacts of each active ingredient and relevant metabolites on endangered or threatened species. Atrazine, propazine, and simazine are all included in a stipulated settlement between the parties in Center for Biological Diversity et al. v. EPA et al. No. 3:11 cv 0293 (N.D. Cal.), and EPA agreed in that stipulated settlement to set August 14, 2021, as the deadline for EPA to make a nationwide effects determination for each active ingredient, and to request any required consultation with the Services, under ESA Section 7(a)(2).
- EPA states that the predominant human health effect of concern for all three of the triazine herbicides and their chlorinated metabolites is potential suppression of the luteinizing hormone (LH) surge, which is considered to be both a neuroendocrine and a developmental effect. Atrazine and simazine were both included on List 1 for screening testing under the EDSP required by the Food Quality Protection Act (FQPA) amendments. All of the required Tier 1 screening assays for each of these substances are complete and have been evaluated by EPA, but EPA has not yet made human health or environmental findings under the EDSP. The EDSP screening testing has not been completed yet for propazine.
Risk Mitigation Measures
Each PID proposes specific risk mitigation measures intended to address potential human and environmental risks identified by the EPA risk assessments.
For atrazine, the PID includes the following measures to mitigate aggregate human risk:
- Reduce the permissible application rates for use of granular and liquid formulations on residential turf.
- Require additional personal protective equipment (PPE) and engineering controls for certain uses.
- Restrict aerial applications to liquid formulations only.
- Limit backpack sprayer applications to landscape turf to spot treatment only.
- Prohibit pressurized handgun application to certain commodities.
To mitigate ecological risks, the atrazine PID proposes to require various spray drift reduction measures, to add a non-target advisory statement to labeling, and to adopt a nationwide stewardship program.
For propazine, the PID proposes to cancel the greenhouse use to mitigate aggregate human risk. Ecological risks would be mitigated by proposing to require various spray drift reduction measures and by adding a non-target advisory statement to labeling.
For simazine, the PID includes the following measures to mitigate aggregate human risk:
- Cancel simazine use on residential turf.
- Require additional PPE and engineering controls for certain uses.
- Limit pressurized handgun applications to certain commodities to spot treatment only.
Ecological risks would be mitigated by proposing to require various spray drift reduction measures and by adding a non-target advisory statement to labeling.
In each of the PIDs for the triazine herbicides, EPA has focused its efforts on adopting mitigation measures which should be efficacious in reducing human and ecological risks without materially impairing the availability of the products in question for key agricultural uses. In some instances, the PID documents explicitly state that the product registrants have agreed to proposed changes. An EPA Pesticide Program Update dated December 19, 2019, that discusses the interim decision for atrazine includes statements of support from several grower groups.
By Lynn L. Bergeson and Carla N. Hutton
On August 26, 2019, the National Institute of Environmental Health Sciences (NIEHS) announced that the results of an NIEHS-funded study show that graphene could provide alternatives to chemicals in insect repellant and protective clothing. The study, “Mosquito Bite Prevention through Graphene Barrier Layers,” was published in the Proceedings of the National Academy of Sciences. According to the abstract, the researchers hypothesized that graphene films may provide mosquito bite protection for light, fiber-based fabrics. The researchers investigated the fundamental interactions between graphene-based films and the mosquito species Aedes aegypti through a combination of live mosquito experiments, needle penetration force measurements, and mathematical modeling of mechanical puncture phenomena. The abstract states that “the results show that graphene or graphene oxide nanosheet films in the dry state are highly effective at suppressing mosquito biting behavior on live human skin. Surprisingly, behavioral assays indicate that the primary mechanism is not mechanical puncture resistance, but rather interference with host chemosensing.” The researchers propose that the interference is “a molecular barrier effect that prevents Aedes from detecting skin-associated molecular attractants trapped beneath the graphene films and thus prevents the initiation of biting behavior.” According to the abstract, placing water or human sweat on the external film surface circumvents the molecular barrier effect. In this scenario, the abstract states, “pristine graphene films continue to protect through puncture resistance -- a mechanical barrier effect -- while graphene oxide films absorb the water and convert to mechanically soft hydrogels that become nonprotective.”
By Lynn L. Bergeson and Carla N. Hutton
On October 19, 2018, the U.S. Environmental Protection Agency (EPA) posted the Final Work Plan (FWP) for the nanosilver registration review process under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The FWP explains what the Office of Pesticide Programs (OPP) “knows about nanosilver generally, highlighting anticipated data and assessment needs for each unique nanosilver chemistry, identifying the types of information that would be especially useful to the Agency in conducting the review, and providing an anticipated timeline for completing review of the nanosilver case.” According to the FWP, EPA has identified the following use patterns to date: swimming pool/spa treatments; and material preservative products for coatings, textiles, and plastics. The FWP states that people may be exposed to nanosilver through inhalation and dermal exposures while applying the products to swimming pools and from incidental oral exposures during swimming. Further exposures may come from material preservative uses either while applying or from nanosilver that leaches out when textiles and plastics are washed. Nontarget organisms can be exposed when swimming pool water is released or when nanosilver used as a material preservative leaches.
According to the FWP, EPA “anticipates the need to require generation and submission of human health hazard and exposure data and to conduct a human health risk assessment for nanosilver during registration review.” The FWP states that EPA plans to conduct an environmental risk assessment for the nanosilver uses, “particularly focusing on materials preservative uses, such as plastics and textiles if the particular nanosilver chemistries are shown to leach, and swimming pool uses.” Any of the other use patterns may also be subject to ecological assessment if the fate and product chemistry profiles indicate the potential for environmental exposures. According to the FWP, the risk assessment integrates the environmental fate and effects data to determine if any uses pose risks to nontarget organisms. Potential risks to fish, aquatic invertebrates, aquatic plants, and birds and mammals will be assessed after the data gaps specified in the FWP are satisfied and the relevant data are available.
EPA invites any label amendments that could be considered to eliminate the anticipated need to require certain data, reduce the possibility that EPA’s planned risk assessments overestimate risk due to reliance on conservative assumptions, and/or improve label clarity. EPA anticipates issuing in 2018 a DCI requiring the data set out in Table 7 of the FWP, “Studies Anticipated as Needed for Nanosilver Registration Review.”
By Lynn L. Bergeson and Carla N. Hutton
On May 19, 2015, the U.S. Environmental Protection Agency (EPA) announced that it issued a conditional registration for a nanosilver-containing antimicrobial pesticide product named “NSPW-L30SS,” or “Nanosilva.” This is the second nanosilver registration issued by EPA and reflects the Agency’s growing expertise in addressing, processing, and approving nanopesticide registration applications. According to EPA, the product will be used as a non-food-contact preservative to protect plastics and textiles from odor- and stain-causing bacteria, fungi, mold, and mildew. Items to be treated include household items, electronics, sports gear, hospital equipment, bathroom fixtures, and accessories. EPA based its decision “on its evaluation of the hazard of nanosilver after reviewing exposure data and other information on nanosilver from the applicant, as well as data from the scientific literature.” EPA states that these data show that treated plastics and textiles release “exceedingly small amounts of silver.” Based on this evaluation, EPA “determined that NSPW-L30SS will not cause unreasonable adverse effects on people, including children, or the environment and that it would be beneficial because it will introduce less silver into the environment than competing products.” EPA notes that it is requiring the company “to generate additional data to refine the Agency’s exposure estimates.” According to EPA, it will post a response to comments received on its 2013 proposed registration decision document, as well as the current decision document, in the rulemaking docket.
By Lynn L. Bergeson and Carla N. Hutton
Almost seven years ago, the International Center for Technology Assessment (ICTA) filed a petition for rulemaking requesting that the U.S. Environmental Protection Agency (EPA) regulate products containing nanosilver as pesticides and for related other forms of relief. On March 19, 2015, EPA responded to the petition. In general, the response does not alter EPA’s legal position with regard to nanosilver and its regulation under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), or otherwise contribute any new interpretations of existing EPA pesticide registration or enforcement policy.
Briefly, the key decisions articulated in EPA’s response to the petition are:
* EPA will treat products containing nanosilver as pesticides under FIFRA if intended for pesticidal purposes, even in the absence of explicit pesticidal claims.
* EPA rejected ICTA’s claim that all products containing nanosilver are categorically pesticides and should be regulated as such.
* EPA will continue to apply its statutory and regulatory criteria as to what is a pesticide on a case-by-case basis. The determination “would be fact specific, typically based upon information on the use patterns intended, the claims or other advertising used to distribute or sell the ingredient or product, and any other information or knowledge made known to or known by the distributor or seller.”
* Importantly, EPA disagrees with ICTA’s claim that the treated article exemption should not apply to any nanosilver pesticide product because nanosilver specifically is not the registered pesticide active ingredient. According to EPA, application of the treated article exemption is available if a registered pesticide product is used, consistent with any terms and conditions of use of the registered product.
* EPA granted ICTA’s request to review the health and safety impacts from use of a nanosilver ingredient in a pesticide product based on nanosilver data for the portion released as nanosilver and based on macro-scaled silver for the portion released as silver ions, and agrees that FIFRA Section 3(c)(7)(C) is the appropriate authority for review of applications for registration of products containing nanosilver ingredients.
* EPA rejected ICTA’s claim that EPA must comply with the National Environmental Policy Act (NEPA) to assess the environmental impacts of EPA’s decision regarding nanopesticides, citing EPA’s well-settled view that it is exempt from NEPA requirements under FIFRA under Merrell v. Thomas, 807 F.2d 776 (9th Cir. 1986).
* EPA denied ICTA’s request to use a particular enforcement strategy to address unregistered pesticides sold or distributed in the U.S., believing that EPA lacks a factual basis to conclude that all nanosilver products are pesticides and thus does not have the legal basis upon which to conclude that all products are illegally sold or distributed.
By Lynn L. Bergeson and Timothy D. Backstrom
On December 16, 2014, the Center for Food Safety (CFS) and its affiliate the International Center for Technology Assessment (ICTA), along with a coalition of other non-governmental organizations, brought suit in the U.S. District Court for the District of Columbia. The suit concerns a May 1, 2008, petition by these organizations requesting that the U.S. Environmental Protection Agency (EPA) take regulatory action concerning nanoscale silver (nanosilver) products, including classifying nanosilver as a pesticide under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Since receiving the CFS/ICTA petition, EPA has taken a number of incremental steps to regulate nanosilver. After inviting comment concerning the petition, EPA referred scientific issues concerning risks from and exposure to nanosilver to the FIFRA Scientific Advisory Panel (SAP), announced that it would treat nanoscale pesticides (including nanosilver) as a separate pesticidal active ingredient, established new registration requirements for several specific nanosilver products, and initiated the registration review process for registered nanosilver products.
Notwithstanding these actions, EPA has not formally responded to the 2008 CFS/ICTA petition, and the petitioners have characterized the steps taken by EPA to date as “toothless.” Rather than contesting the suit, EPA may seek an agreement requiring EPA to respond formally to the petition by a specified date. Perhaps EPA will characterize the regulatory actions taken to date as a partial grant of the petition. On the other hand, many of the nearly 400 nanosilver products that CFS/ICTA claim EPA should regulate under FIFRA have no pesticidal claims or purpose or are being sold and distributed outside of the U.S. With respect to these products, EPA will likely respond that it has no authority to provide the relief sought by the petitioners.