The risk assessment for birds and mammals uses a tiered approach to assess the risk of mortality and reproductive effects. Ecotoxicology often works in collaboration with toxicology, particularly when establishing mammalian endpoints for use in the risk assessment.
This page explains the main guidance available for Great Britain and Northern Ireland. The Health and Safety Executive (HSE) has fully reviewed the implications of any changes in requirements for bird and mammal risk assessment of plant protection products before updating our guidance.
The page includes a link to a report summarising those changes, and stakeholders’ comments on them.
Please note that HSE’s approach for considering risks to birds and mammals from plant protection products containing multiple active substances will be updated in future, in response to changes in guidance.
You can also read about the background to HSE’s review of these guidance changes for bird and mammal risk assessment for plant protection products (in the National Archives).
Toxicity studies
Organisation for Economic Co-operation and Development (OECD) guidelines for toxicity studies are available on the OECD website.
Main guidance documents
Great Britain (GB)
On 17 August 2026, the Health and Safety Executive (HSE) adopted the 2023 European Food Safety Agency (EFSA) guidance document for risk assessment for birds and mammals (EFSA-Q-2017-00555) with clarifications for GB assessments.
This replaces the previous 2009 EFSA Guidance document for Risk Assessment for Birds and Mammals (EFSA-Q-2009-00223).
From 17 February 2027, any applications for active substance approvals or plant protection product authorisation in Great Britain, which rely on a new bird and mammal risk assessment, must take account of the 2023 EFSA guidance. Applicants are able to voluntarily use this guidance from 17 August 2026. Adopting the updated guidance aligns Great Britain with the EU process.
The following clarifications apply to the use of the 2023 EFSA guidance in GB submissions. They reflect national requirements and enable practical implementation of the guidance. They are appropriate for a national regulator to determine to ensure that the same, high standards of protection continue to be met.
Benchmark dose (BMD): until the BMD for the active substance has been derived as part of the approval or renewal of approval of the active substance, the ‘no-observed-adverse-effect level’ (NOAEL) will be used for product authorisations (unless the agreed active substance endpoint is already a BMD10).
Time weighted average factor (TWA): until the TWA approach specified in the 2023 EFSA guidance has been agreed as part of the approval or renewal of approval of the active substance, product risk assessments should be conducted using the TWA approach specified in the 2009 EFSA guidance.
Where the critical endpoint for the reproductive risk assessment is based on effects on eggshell thickness or is derived from an acute toxicity study, a TWA of lower than 1 should not be used.
Secondary poisoning and drinking water: until the corresponding guidance has also been implemented, consideration of exposure through benthic invertebrates and soil pore water is not required.
Field monitoring studies: recommendations in the 2023 EFSA guidance regarding the use of higher tier studies should be considered in a GB context, reflecting the lower diversity of conditions the assessment is required to cover. The use of the Critical Appraisal Tool (CAT) approach for higher tier study evaluation is considered optional for GB submissions.
Metabolites: ecotoxicologically relevant metabolites identified during the most recent active substance evaluation should be considered in GB product risk assessments, whether the active substance assessment was conducted to the 2023 or 2009 EFSA guidance.
Find out more
Further information can be found in GB adoption of the 2023 EFSA guidance on risk assessment for birds and mammals: Summary of key changes and stakeholder comments.
Northern Ireland
On 1 October 2025 EFSA Guidance document for Risk assessment for Birds and Mammals (EFSA-Q-2017-00555) came into force in the EU for active substances and plant protection products. This guidance applies directly in Northern Ireland.
Since 1 October 2025, any application submitted in Northern Ireland, which relies on a new bird and mammal risk assessment, must take account of the 2023 EFSA guidance for:
- a new plant protection product authorisation, or
- the renewal of a plant protection product
HSE has considered how applicants should approach certain aspects of this guidance for product authorisations and provides the following clarification.
Benchmark dose (BMD): until the BMD for the active substance has been derived as part of the approval or renewal of approval of the active substance, the ‘no-observed-adverse-effect level’ (NOAEL) will be used (unless the agreed active substance endpoint is already a BMD10).
Time-weighted average factor (TWA): until the approach on the use of TWA for the active substance has been agreed as part of the approval or renewal of approval of the active substance, the product risk assessments should be submitted and conducted to HSE using the TWA approach specified in the 2009 EFSA guidance. If an EU Member State has decided that a TWA should be used according to the approach specified in the 2023 EFSA guidance, HSE will accept that decision. The necessary supporting assessment should be provided to HSE to accept and evaluate the risk assessment using the same approach.
Previous guidance documents
EFSA Guidance document for Risk Assessment for Birds and Mammals (EFSA-Q-2009-00223)