U.S. EPA announces proposed new mitigation measures for rodenticides

On November 29, 2022, the U.S. Environmental Protection Agency (EPA) announced proposed new mitigation measures for 11 rodenticides, including measures to reduce potential exposures to three federally listed endangered and threatened species and one critical habitat. The mitigation measures are part of EPA’s goals outlined in its April 2022 Endangered Species Act (ESA) Workplan and one of the ESA pilots described in its November 2022 update.

Comments on the proposed interim decisions (PIDs) are due on or before February 13, 2023, in the following pesticide registration review dockets:

• Brodifacoum, EPA-HQ-OPP-2015-0767;
  

• Bromadiolone, EPA-HQ-OPP-2015-0768;
  

• Bromethalin, EPA-HQ-OPP-2016-0077;
  

• Chlorophacinone, EPA-HQ-OPP-2015-0778;
  

• Cholecalciferol, EPA-HQ-OPP-2016-0139;
  

• Difenacoum, EPA-HQ-OPP-2015-0769;
  

• Difethialone, EPA-HQ-OPP-2015-0770;
  

• Diphacinone (and its sodium salt), EPA-HQ-OPP-2015-0777;
  

• Strychnine, EPA-HQ-OPP-2015-0754;
  

• Warfarin (and its sodium salt), EPA-HQ-OPP-2015-0481; and
  

• Zinc Phosphide, EPA-HQ-OPP-2016-0140.
  

As background, in 2008, EPA issued a risk mitigation decision (RMD) for 10 rodenticides that set forth mitigation measures to reduce risks to human health and non-target organisms, including implementing minimum packaging size requirements for products on the consumer market (must be in packages one pound or less), prohibiting products intended for general consumers (i.e., homeowners or residential consumers) from containing second-generation anticoagulant rodenticides (SGAR), and requiring tamper- and weather-resistant bait stations for outdoor, above-ground placements where children, pets, and wildlife may be present. The 2009 RMD represented EPA’s final decision on the reregistration eligibility of rodenticide products at that time and constituted EPA’s final action.

The PIDs cover three first-generation anticoagulant rodenticides (FGAR), four SGARs, and four non-anticoagulant rodenticides. Strychnine (the 11th rodenticide) was not part of the 2008 RMD but is now included as part of EPA’s registration review of the rodenticide group.

The PIDs propose additional mitigation measures based on findings in the 2020 draft human health and ecological risk assessments (DRA) and comments submitted on the DRA. According to EPA, these measures are intended to reduce exposure to non-target organisms. Proposed measures include requiring bait to be placed in tamper-resistant bait boxes to ensure it is contained and requiring users to collect carcasses of rodents that may have consumed rodenticides to prevent further exposures to non-target organisms that could consume the carcasses. In addition, in its PIDs EPA proposes that all products, excluding those registered solely for use by homeowners, include label language directing users to access the web-based Bulletins Live! Two and follow the measures contained in any Endangered Species Protection Bulletin(s) for the area in which the user is applying the product.

EPA states the ESA workplan describes how it is developing early mitigation for a subset of species where EPA predicts a likelihood of a jeopardy or adverse modification finding for one or more of the registration review pilot pesticides if mitigation is not undertaken. One of these pilots is for rodenticides, which will focus on addressing effects to mammals and birds that consume rodenticide bait (primary consumers) and to birds, mammals, and reptiles that consume primary consumers (secondary consumers).

According to EPA, as part of its registration review ESA pilot for the rodenticides, EPA evaluated their potential effects on individuals and populations of Stephens’ kangaroo rat, Attwater’s prairie chicken, and the California condor and its designated critical habitat. EPA states it chose these three listed species because they represent species that may be affected by rodenticides through different routes of exposure (e.g., primary consumption by Stephens’ kangaroo rat and Attwater’s prairie chicken, secondary consumption by California condor). EPA’s draft evaluation determined that rodenticide use is ″likely to adversely affect″ these three species but predicted the proposed mitigations will protect them from likely ″jeopardy″ (i.e., potential impacts to the survival of listed species) and ″adverse modification″ of critical habitat. A ″likely to adversely affect″ determination means EPA reasonably expects that at least one individual animal of any of the three species may be exposed to one or more of the rodenticides at a sufficient level to have an adverse effect. While EPA has made predictions about the likelihood of jeopardy and adverse modification, the U.S. Fish and Wildlife Service (USFWS) is responsible for making the actual jeopardy/adverse modification findings for these species and has the sole authority to do so.

To focus the mitigations where they are most needed while retaining options for rodenticide users, EPA states the proposed mitigation measures for the three listed species would be targeted in specific geographic areas most relevant to the species. The PIDs include proposed mitigation measures to be included on the Bulletins Live! Two website for the species and the critical habitat of the California Condor. The draft evaluation for the three species and one critical habitat and associated mitigation measures are pilots for other listed species that may be similarly exposed and affected by rodenticides. In developing and applying mitigation measures for these species, EPA stated that it recognized that not all rodenticides have the same effects.

In addition to describing the pilot and the mitigation measures for the selected species, the PIDs also describe EPA’s plans for expanding those mitigation measures to the other approximately 90 listed species potentially affected by rodenticides. When this plan is issued in final, it will be known as the Rodenticide Strategy that EPA described in its November 2022 update to its ESA Workplan.

EPA also announced it intends to make effects determinations for all listed species available in a draft biological evaluation (BE), which EPA anticipates making available for public comment in November 2023. The BEs will contain EPA’s draft analysis of the potential effects of the rodenticides on listed species and their designated critical habitats and will identify mitigation measures for these species and critical habitats to avoid or minimize exposure from the rodenticides. EPA expects to complete the final BE for the rodenticides in November 2024.

If EPA’s final BE continues to find that rodenticide use is likely to affect adversely listed species or adversely modify their critical habitats, then EPA will initiate formal consultation and share its findings with the USFWS, which in turn can use the information in EPA’s BE to inform its biological opinions. If the USFWS determines in its final biological opinions that additional mitigations are necessary to address any jeopardy or adverse modification determination, or to address any incidental take, then EPA will work to ensure that any necessary registration or labeling changes are made.

Additional information on EPA’s rodent control pesticide safety review is available here.

Commentary

The proposed interim decisions cover the full ″rodenticide cluster″ -- seven anticoagulant rodenticides and four non-anticoagulant rodenticides. Strychnine (the 11th rodenticide) was not part of the 2008 Risk Management Decision but is now included as part of EPA’s registration review of the rodenticide group.

EPA has determined that rodenticide use is ″likely to adversely affect″ three representative species but also predicts that the proposed mitigations will protect them from likely ″jeopardy.″ Note that while EPA has made predictions about the likelihood of jeopardy and adverse modification, the USFWS is responsible for making the actual jeopardy/adverse modification findings for these species and has the sole authority to do so. As stated above, EPA intends to make effects determinations for all listed species (about 90 species) available in a draft BE in November 2023, and EPA expects to complete the final BE for the rodenticides in November 2024. In short, this November 2022 action represents a mid-point, not a starting point or endpoint, for action on rodenticides, and EPA’s approach on addressing endangered species will be a good indicator of how well the ESA Workplan process and approach are working over the coming months.

Requiring bait to be placed in tamper-resistant bait boxes to ensure it is contained is a common, straightforward measure and generally follows current practices. Requiring users to collect carcasses of rodents that may have consumed rodenticides can be difficult to measure compliance and to enforce and also raises different public health concerns; we expect this approach to be debated further. In addition, the proposed interim decisions would require that all products -- excluding those registered solely for use by homeowners -- include label language directing users to access the web-based Bulletins Live! Two and follow the measures contained in any Endangered Species Protection Bulletin(s) for the area in which the user is applying the product. Understanding this process and the map for the user’s region specifically will be a process that applicators adjust to over time, but the quality and clarity of EPA’s assessments and maps will be important and need improvements. The Bulletins Live! Two system will need continuous investment and improvements to be effective, and linking all of these interactive processes (e.g., rodenticide strategy, ESA Workplan, web-based mapping and announcement systems) could prove cumbersome over time if not managed closely.

Overall, this continues the pesticide program’s march through the thicket of ESA decisions that must be made over the next many years. EPA is using its revised approach as outlined in earlier announcements regarding how it will attempt to comply with ESA as part of the registration and registration review process. The positive news is that EPA is starting to make progress on ESA compliance, which has long been discussed as part of program planning and in response to numerous ESA lawsuits over the past many years. Less clear is how EPA’s requirements will be able to be implemented and/or enforced, and how attempts to implement or comply with label changes might result in controversies among applicators and users of the affected pesticide products. The feasibility and acceptability of some label requirements are among the open questions about EPA’s new approaches to address this long-standing issue.