PPC119 | TECHNICAL

John Horsley spoke at a BPCA Digital Forum about environmental risk assessments (ERAs) – essential for protecting wildlife, complying with the CRRU code, and staying within the law. Here's a summary of his insights.

SPEED READ

• Rodenticides (especially AVKs) can harm birds and mammals directly (primary poisoning) or indirectly (secondary poisoning).
• Under stewardship rules, pest professionals must complete an ERA if there’s a significant risk to non-targets and the environment.
• Before using an AVK, survey for non-target species, watercourses, and other environmental risks, then record your findings.
• An ERA is your due diligence if a non-target poisoning incident is investigated. Keep good records of what you used, why you used it, and the measures you took.
• Permanent baiting now requires strict justification. Follow CRRU guidance closely if you consider it.

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Understanding environmental risk assessments

Rodenticides and the bigger picture
Rodenticides, commonly known as anticoagulant vitamin K antagonists (AVKs) remain a vital tool against rodents, especially rats and mice. But every use carries potential risks to the environment:

• Bioaccumulation
• Once ingested, AVKs can remain in an animal’s tissue for a long time. A predator that eats contaminated prey may receive a secondary dose.
• Long half-life
• The toxicity can persist in tissues, posing a threat to predators or scavengers up the food chain.
• Hazards to wildlife
• AVKs can affect all birds and mammals. If mishandled, they may also enter watercourses, endangering fish and aquatic ecosystems.

Because of these concerns, AVKs are classified as “candidates for substitution.” If a safer, equally effective alternative becomes available, the rodenticides we rely on might be phased out. Hence, the industry must act responsibly to keep these tools available.

Primary vs secondary poisoning

• Primary poisoning - A non-target organism (such as a songbird or even fish, if bait enters waterways) directly consumes the rodenticide.
• Secondary poisoning - A predator bird, mammal, or scavenger (think buzzards, barn owls, or foxes) eats a poisoned rodent or insect and ingests rodenticide residues.

Both scenarios emphasise the need for careful usage and disposal protocols. Data from the last 50 years shows that a wide variety of species can be harmed, ranging from cats and dogs to raptors and badgers. 

As John explained, top-ten lists of contaminated species often feature buzzards, kites, foxes, barn owls, and more. Monitoring by organisations such as CRRU reveals that rodenticide residues remain a problem in many wild birds.

The legal imperative

When you use rodenticides, you must conduct an environmental risk assessment (ERA) to show you’ve considered and mitigated risks:

• Stewardship scheme - In the UK, the Campaign for Responsible Rodenticide Use (CRRU) oversees stewardship guidelines to reduce rodenticide impacts on non-target wildlife. Compliance is checked through residue testing in barn owls and other species.
• Potential prosecutions - Pest controllers have faced legal action for improper rodenticide use. Even if a non-target animal dies of other causes (eg, road traffic collisions) but is found with high rodenticide residues, investigators will look for where and how it was exposed.

John highlighted a 2011 prosecution: a dead fox tested positive for rodenticides, and a pest controller was charged with failing to produce a proper environmental risk assessment and using AVKs improperly. ERAs are thus a cornerstone of legal defence, proving your professionalism and diligence.

Building your environmental risk assessment

1. The site survey

Before completing an ERA form, conduct a thorough site survey:

• Identify the infestation: Is it rats, mice, or both? Indoors or outdoors?
• Check for non-targets: Which birds of prey are in the area? Are there dogs, cats, or livestock on site? Any watercourses, ponds, or protected habitats?
• Assess the pest situation: How large or entrenched is the infestation? What are the potential reinfestation risks?

Record these details in a site survey report and assign it a unique reference number. If you detect a significant risk to non-targets from using AVKs, proceed with a dedicated ERA.

2. Filling out the ERA

CRRU has a standard ERA template (downloadable at thinkwildlife.org):

• Risk factors: Document all potential non-target species on or near site and the likelihood of them coming into contact with the bait.
• Justification: Why are rodenticides necessary here? Could other methods suffice, such as trapping, proofing, or housekeeping improvements?
• Site specifics:Note any watercourses, special scientific interest areas, farmland restrictions, or local wildlife trusts’ protections.
• Bait choices: Which product are you using (including active ingredient and concentration)? Which species is it licensed for? (Bear in mind, many AVKs cannot legally be used for wood mice or 
  field mice.)
• Risk mitigation: Outline how you’ll protect non-targets, for instance by using tamper-resistant bait stations, placing bait only in secure or inaccessible areas, or removing any 
  leftover bait immediately after the infestation is controlled.

3. Follow the CRRU risk hierarchy

In integrated pest management (IPM), lethal control (including AVKs) should be a last resort if non-toxic methods alone aren’t sufficient. CRRU’s hierarchy reminds you to:

• Always consider proofing, hygiene, and housekeeping. Restrict rodent access and remove attractants.
• Consider traps or alternative active substances. For house mice indoors, alpha-chloralose or cholecalciferol might be more appropriate.
• Use AVKs responsibly. If you must, confine rodenticide use to essential areas, document your choices, and check the bait and carcasses frequently.

4. Monitoring and disposal

Rodents killed by AVKs can still pass on harmful residues if scavenged. The product label and CRRU guidance both emphasise:

• Frequent carcass checks. The label’s recommended frequency for visiting bait points often matches how 
  often you should remove carcasses. In heavy infestations, more frequent checks may be needed.
• Safe disposal. Confirm whether you can incinerate carcasses on a farm, or place them in double-bagged waste if permitted by local authority guidelines. Always keep records.
• Waste carriers licence. As John mentioned, if you’re transporting any form of waste (e.g., used bait, dead rodents) in a commercial capacity, a waste carriers licence is mandatory (though the lower-tier licence is free).

5. Permanent baiting (caution required)

Permanent outdoor baiting was once standard, but the potential for non-target harm is high. The CRRU code makes it clear:

• Only in exceptional cases. If there’s a real, ongoing risk (eg, critical sites where re-infestation is certain), you 
  must document why permanent baiting is necessary.
• Follow label and CRRU guidelines. The product label might prohibit permanent baiting or limit it to specific circumstances. Failing to comply could lead to enforcement actions.
• Audit trail. Justify permanent baiting with site data (previous large-scale infestations, high-risk premises, etc). Even then, you must regularly inspect and remove bait if it’s not actively in use.

"Keeping rodenticides available depends on evidence we can use them responsibly."

Common questions and clarifications

Is an ERA needed for indoor-only house mouse treatments?
Even inside a domestic roof space, you should assess risk. While the exposure risk outdoors is lower, you still need to consider whether non-target species could access the bait (eg, pets or children). Document either:

• A short-form ERA - If the risk is minimal, record the reasoning in your site notes.
• Full CRRU-approved ERA - If any external risk or potential non-target presence is identified.

How often must I redo an ERA on contract sites?
Each time you use rodenticides. An annual or one-off site survey can gather broad environmental data, but any new rodenticide application should be backed by up-to-date information and an ERA referencing that site survey.

What if barn owls or raptors are common nearby?
If your site is in an area known for high bird-of-prey populations (e.g., red kite hotspots), you’ll need heightened caution. Your ERA should reflect that you’re aware of these species, and any rodenticide use is planned to minimise risk, potentially leaning more on non-toxic or alternative methods.

What about watercourses or farmland run-off?
Rodenticides in flood zones can end up in rivers. Part of your ERA is ensuring baits are protected from the elements and removed if severe weather threatens. You should also consider adjacency to farmland or run-off channels. Proof your bait placements against rain, flooding, and wildlife intrusion.

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2026 and beyond

CRRU-APPROVED CPD
To continue to purchase rodenticides in 2026, you must complete three hours of CRRU-Approved CPD in 2025 and register it on an CRRU-Approved CPD scheme, such as BPCA Registered.

Online CPD
An online CPD quiz based on this feature is now available on the BPCA website. BPCA Registered members and anyone with a MyBPCA account can take a CPD quiz at any time bpca.org.uk/find-cpd or sign up at

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