California Cut Second-Generation Rodenticide Use by 85 Percent. Wildlife Exposure Barely Moved

Two records that should move together

California’s AB 1788 restricted brodifacoum, bromadiolone, difenacoum and difethialone from January 2021, to protect wildlife. Our analysis of the restriction’s effect on pest control found structural applications of those compounds fell from 2,128,528 in 2020 to 310,290 in 2021 and 263,926 in 2023. If wildlife exposure followed use, residues in wildlife should have fallen too.

The California Department of Fish and Wildlife’s Wildlife Health Laboratory tests dead wildlife for rodenticide residues every year. Its 2024 annual report includes a five-year summary table, which lets the two records be set side by side.

Use fell

Exposure did not

Sources: California Department of Fish and Wildlife, Wildlife Health Laboratory, 2024 Annual Report, Table 21, summarising the 2020 to 2024 annual reports; California Department of Pesticide Regulation, Pesticide Use Reports, site code 10. Exposure covers all anticoagulants, first and second generation. Author compilation.

What it means. The share of tested wildlife with anticoagulant residues stayed between 67.9 and 81.0 percent in every year from 2020 to 2024, while structural second-generation use stayed about 85 percent below its 2020 level from 2021 onward. Confirmed or suspected toxicosis cases did fall, from 24 in 2020 to between 11 and 19 a year after, and as a share of exposures from 22.2 to about 12 percent.

What limits it. The laboratory notes that its surveillance has “species, spatial, and diagnostic biases”, including that screening is typically done on suspected cases, so the share exposed is not a population rate. Exposure here includes first-generation anticoagulants such as diphacinone, whose use rose as second-generation use fell.

Second-generation residues are still the most common

The 2024 report shows the restricted compounds remain widespread. Of 54 raptors tested, 24, or 44.4 percent, carried second-generation residues and 16, 29.6 percent, first-generation; brodifacoum, bromadiolone and difethialone were the most common. Among 97 non-game mammals, the laboratory recorded 117 second-generation detections against 97 first-generation. In mountain lions, 39 of 41 tested were exposed, with 57 second-generation and 56 first-generation detections.

The laboratory writes that brodifacoum can have a half-life of approximately 350 days in liver tissue, and that exposures detected in 2024 “were most likely related to use after AB1788 was implemented (January 1, 2021)”. In other words, the residues are not simply leftovers from before the restriction.

Why the two records can diverge

These data cannot say which explanation is right, but several are consistent with them. The restriction exempts some uses, including agriculture-linked sites such as food warehouses; our county analysis found 263,926 structural applications remaining in 2023, two thirds of them made by ten licences. Agricultural and other non-structural uses are outside our structural figures. Residues persist for months. And testing concentrates on animals suspected of poisoning. Our analysis of the 2022 wildlife data covers the testing programme in detail.

Checks

1. Source of the series

Method. The five-year series is taken directly from Table 21 of the laboratory’s 2024 annual report, which states it summarises the 2020 to 2024 reports.

2. Use figures

Method. Structural applications of brodifacoum, bromadiolone, difenacoum and difethialone from the application count field of the Pesticide Use Reports, site code 10.

Download the data

The tables in this report are published as CSV files under a Creative Commons Attribution 4.0 licence. You may republish, remix and build on them, including commercially, with attribution to The Pest Control Brief and a link to this page.

• Wildlife anticoagulant exposure and toxicosis, 2020 to 2024, with structural second-generation applications (CSV, 5 rows)

How to cite this report

The Pest Control Brief, “California Cut Second-Generation Rodenticide Use by 85 Percent. Wildlife Exposure Barely Moved”, 2 October 2026. https://thepestcontrolbrief.com/rodenticide-ban-wildlife-outcome/

References

1. California Department of Fish and Wildlife, Wildlife Health Laboratory. 2024 Annual Report: Pesticide Exposures and Mortalities in Non-target Wildlife (2025). nrm.dfg.ca.gov document 241288. Accessed 5 October 2026.
2. California Department of Pesticide Regulation. Pesticide Use Report annual archives, 2020 to 2023. files.cdpr.ca.gov/pub/outgoing/pur_archives/. Accessed 2 October 2026.
3. California Legislature. AB 1788, California Ecosystems Protection Act of 2020. leginfo.legislature.ca.gov AB 1788. Accessed 2 October 2026.

How the comparison was built

Wildlife. Annual totals of animals tested for anticoagulant rodenticides, exposed, and confirmed or suspected toxicosis, from the laboratory’s own five-year table; 2024 species detail from the same report.

Use. Structural pest control applications only; agricultural and other uses are excluded.

Limitations. Surveillance is not a random sample. 2024 use data are not yet published. Exposure counts include first-generation compounds.

Last reviewed: 5 October 2026.

For environmental reporters

Most quotable statistics

1. Structural use of second-generation anticoagulant rodenticides in California fell 85 percent after 2021.
2. The share of tested wildlife with anticoagulant residues was 67.9 percent in 2020 and 68.7 percent in 2024.
3. 39 of 41 mountain lions tested in 2024 were exposed to anticoagulant rodenticides.
4. 44.4 percent of raptors tested in 2024 carried second-generation residues.
5. Toxicosis cases fell from 24 in 2020 to 14 in 2024.

Press summary

California’s restriction on the most toxic rat poisons sharply cut their use by pest control businesses but has not reduced how often they turn up in wildlife, according to an analysis by The Pest Control Brief of state pesticide use reports and state wildlife testing. Structural applications of second-generation anticoagulants fell 85 percent after 2021, yet the share of tested animals with anticoagulant residues was 68.7 percent in 2024, against 67.9 percent in 2020. Thirty-nine of 41 mountain lions tested in 2024 were exposed. Poisoning deaths did fall.

Headlines editors could use

1. California cut rat poison use 85%. Wildlife exposure didn’t budge
2. 95% of mountain lions tested still carry rat poison
3. The rodenticide ban’s missing wildlife dividend

Questions

Has California’s rodenticide ban reduced wildlife poisoning?

Exposure has not fallen: 67.9 percent of tested wildlife carried anticoagulant residues in 2020 and 68.7 percent in 2024. Confirmed or suspected toxicosis cases fell, from 24 to 14.

Are mountain lions still exposed to rat poison?

Yes. 39 of 41 mountain lions tested by the state wildlife laboratory in 2024 had anticoagulant rodenticide residues.

Why are banned rodenticides still found in wildlife?

Exempt uses continue, residues persist for months, and testing focuses on suspected cases. The laboratory says 2024 exposures were most likely related to use after the restriction began.

How much did pest control use fall?

Structural applications of second-generation anticoagulants fell from 2,128,528 in 2020 to 263,926 in 2023.

Where can I get the data?

The five-year series is in the CSV above.