EPA Releases Draft Biological Evaluation of 11 Rodenticides’ Effects on Endangered Species

For Release December 1, 2023

The U.S. Environmental Protection Agency (EPA) is releasing a draft Biological Evaluation (BE) that includes EPA’s draft effects determinations for federally listed and proposed threatened and endangered (“listed”) species and critical habitats for 11 rodenticide active ingredients. The draft BE (once finalized) will serve as the Agency’s Rodenticide Strategy as outlined in EPA’s Endangered Species Act Workplan to guide how the Agency addresses mitigation for rodenticides going forward and will be available for public comment for 60 days.

Each year, rodents cause significant damage to property, crops, and food supplies across the United States. They may also spread diseases, posing a serious risk to public health. Rodenticides are used in residential, agricultural, and non-agricultural settings to control a variety of pests including house mice, Norway rats, roof rats, moles, voles, pocket gophers, prairie dogs, ground squirrels, feral hogs, and mongooses.

The 11 rodenticides evaluated in the draft BE are:

• chlorophacinone,
• diphacinone and its sodium salt,
• warfarin and its sodium salt,
• brodifacoum,
• bromadiolone,
• difenacoum,
• difethialone,
• bromethalin,
• cholecalciferol,
• strychnine, and zinc phosphide.

EPA released a draft human health and ecological risk assessment on these rodenticides in 2020, which was followed by a public comment period during which EPA received valuable feedback. In November 2022, EPA proposed measures for multiple rodenticides—including the requirements of tamper-resistant bait boxes and rodent carcass collection—based on the assessment that addressed protections for specific listed species and critical habitat as part of a pilot program, and has received valuable feedback on those measures as well.

In the draft BE released today, EPA evaluated these rodenticides to determine whether they may affect any listed species or their critical habitats. These evaluations include all listed species and critical habitats as well as all registered uses and currently approved product labels for pesticide products containing these chemicals. The draft BE also identifies species that could potentially be jeopardized and be subject to incidental take.

Based on the findings in this draft BE, EPA determined some changes were needed including adding new measures not in the pilot (i.e., prohibiting application directly to water) and modifying measures (i.e., no longer prohibiting application in areas adjacent to species range or critical habitat because drift is not anticipated). EPA built upon the previous mitigation proposals from the 2022 proposed measures and pilot program to develop a list of mitigation options to be considered in this draft BE and will include a definitive list of measures upon finalizing the BE, which will serve as the Rodenticide Strategy. The finalized materials will help EPA meet its obligations under the Endangered Species Act (ESA).

As part of this analysis, EPA evaluated the effects of the 11 rodenticides on 1,784 listed species and 904 designated critical habitats in the United States and its territories. EPA determined that these rodenticides:

• will cause no effect (NE) on 1,576 listed species (88%) and 857 critical habitats (95%).
• are not likely to adversely affect (NLAA) 72-199 listed species (4%-11%, depending on the chemical and application type) and 9 critical habitats (1%).
• are likely to adversely affect (LAA) 9-136 listed species (1%-8%, depending on the chemical and application type) and 38 critical habitats (4%).

The “likely to adversely affect” (LAA) determination means that EPA reasonably expects that at least one individual animal or plant, among a variety of listed species, may be exposed to the pesticide at a sufficient level to have an adverse effect. The likely “take,” which includes unintentional harm or death, of even one individual of a species, is enough to trigger an LAA determination. As a result, there are often a high number of LAA determinations in a BE. An LAA determination, however, does not necessarily mean that a pesticide is putting a species in jeopardy.

For those species and critical habitats where EPA made an LAA determination, EPA also included its prediction of the potential likelihood of future jeopardy (J) for a listed or proposed species, or adverse modification (AM) of any designated or proposed critical habitat (collectively abbreviated as J/AM). EPA predicts that currently labeled uses of the 11 rodenticides may lead to the potential likelihood of future jeopardy of less than 5% of listed species and the potential likelihood of future adverse modification of less than 1% of the critical habitats. While EPA is not required to include J/AM predictions or draft mitigation measures in its effects determinations, EPA is including this analysis to help expedite the consultation process with the U.S. Fish & Wildlife Service and the National Marine Fisheries Service (the “Services”). The Services are responsible for making the J/AM findings contained in any biological opinion.

This draft BE will be open for public comment for 60 days on www.regulations.gov at docket ID EPA-HQ-OPP-2023-0567. After considering the public comments received on the draft BE, EPA will make appropriate changes to the assessment and revisions to the mitigation measures, issue a final BE, and initiate formal consultation, as appropriate, with the Services. During formal consultation, the Services use EPA’s effects determinations to inform their biological opinions, which would include the final determinations of whether a pesticide jeopardizes listed species and/or adversely modifies critical habitats.

Learn more about EPA’s plans to meet its ESA obligations on the EPA website.