Birds and Mammals

The risk assessment for birds and mammals uses a tiered approach to assess the risk of mortality and reproductive effects, the current guidance document is the European Food Safety Standards (EFSA) guidance document for risk assessment for birds and mammals ((EFSA-Q-2009-00223). Ecotoxicology often work in collaboration with toxicology, particularly when establishing mammalian endpoints for use in the risk assessment.

Toxicity Studies

OECD guidelines for toxicity studies are available on the OECD website.

Current Main Guidance Document

EFSA Guidance document for Risk Assessment for Birds and Mammals (EFSA-Q-2009-00223)1. Whilst using the EFSA Guidance Document of Risk Assessment for Birds and Mammals (EFSA-Q-2009-00223) several errors in the text have been noticed. These have been collected in a document which will be updated if additional errors are found. In addition, clarification is helpful in some areas, so these have also been included.

Previous Guidance Document

Additional Guidance on Specific Issues

Formulation guidance

For guidance on the need for ecotoxicology formulation studies and their use in risk assessment, along with how to consider the combined risk for relevant groups, use the link below.

Risk assessment for plant protection products with multiple active substances

When a product has more than one active substance, the potential additional risks to birds and mammals must also be considered. Reference can be made to the HSE formulation guidance. Notes on some common queries are below.

Active substances may cause the same toxic effects within test organisms. In such cases a combined assessment is required for acute and long-term effects on birds and mammals. Applicants should note that this is relevant for all formulation types, ie seed treatments, granules and foliar sprays.

The Environmental Panel of the Advisory committee on Pesticides (meeting108) has proposed the following tiered approach to bird and mammal risk assessments:

  • Is one active substance clearly driving the risk assessment?
  • Does the Tier I risk assessment for all active substances within the formulation pass with a margin of safety?
  • Did the mammalian toxicology assessment identify that a combined assessment was not required?

If the answer to any of these is yes, a combined risk assessment is probably not required and a reasoned case should be presented. Otherwise, further consideration of combined risk is required.

If a combined risk assessment is required, the acute risk assessment can be performed using the Finney equation, as outlined in the HSE formulation guidance.

For the long-term risk assessment, HSE will apply the recommendations of Appendix B of EFSA (2009) which uses a toxic unit approach for the Tier I formulation assessment. If the Tier I risk assessment fails, then further refinements will be required. Refinements may involve the standard ecological refinements outlined in EFSA (2009) or may be based on a toxicological argument. N.B. HSE do not consider it necessary to conduct additional toxicity studies when making these refinements.

Applicants are welcome to contact HSE to discuss possible refinement options (eg risk characterisation of each active substance, phase-specific approach (Appendix J of EFSA (2009)) on a case-by-case basis.

De-husking of seeds by small mammals

During evaluation of seed treatment applications, the risk assessment for small mammals frequently needs to be refined to determine whether the risk is acceptable. In such cases, applicants often use de-husking behaviour to mitigate the risk to mammals. In order to accept a quantitative refinement of de-husking, robust support of the value used is required by HSE. Since there is very little robust information on de-husking behaviour in small mammals, HSE commissioned a new research project (PS2349), to investigate the role de-husking plays in reducing pesticide exposure to mammals and to develop a methodology to calculate rates of de-husking for different seed types. The Final Report Dehusking of seed by small mammals - default values for use in risk assessment. - PS2349 has been published on the Defra website and the implications of this research have been considered by HSE.

Availability of treated seed on the soil surface after drilling

During evaluation of seed treatment applications, the risk assessments for birds and mammals often need to be refined to demonstrate whether the risk is acceptable. Prior to refinement, the risk is contextualised by estimating the area that would need to be foraged by a bird or mammal to obtain a lethal dose, using seed availability data. That is, if an unfeasibly large foraging area is required for a relevant focal species to obtain a lethal dose, it may be possible to conclude that the risk is low. Conversely, if a lethal dose can be obtained from an area that is clearly small enough for a focal species to forage in a short period of time, this confirms a cause for concern. Since there are very limited UK-specific data available, HSE commissioned a research project (PS2334) to investigate seed availability on the soil surface after drilling for a range of arable crops. The Final Report Assessment of the availability of seed on the soil surface after drilling - PS2334 has been published on the Defra website and the regulatory implications of this research have been considered by HSE.

Zonal harmonisation: Birds and Mammals Risk assessment

Under this interim scheme for minor crops in accordance with Regulation 1107/2009 (as it applies in Northern Ireland), which forms part of a wider programme of measures to secure early benefits from zonal harmonisation, relevant applications will not be subject to a review of the bird and mammal risk assessment. While there is some way to go before a fully harmonised approach to bird and mammal risk assessment and risk mitigation and associated management is agreed, this scheme is an interim measure until greater harmonisation is achieved.

UK position paper on Ludwigs et al. (2017)

This paper on the UK HSE position on the use of Monte-Carlo simulated PT value covers:

  1. Background to the parameter in pesticide risk assessment and possibilities for its refinement
  2. A HSE summary of the paper by Ludwigs et al. (2017)
  3. HSE discussion of the 21-d PT concept and Ludwigs et al. (2017) example
  4. HSE conclusions/recommendations

Spreadsheets to help with risk assessment

HSE is not responsible for the accuracy or use of any endpoints derived using the following.

To download the spreadsheets, right click on the link and select 'Save As...' or 'Save Target As...' from the menu. You can then save the spreadsheet to your computer.

Proportion of different food types in the bird and mammal diet

PD - the proportion of different food types in the bird and mammal diet, is one of the refinement steps discussed in the EFSA Guidance Document on Risk Assessment for Birds and Mammals (EFSA, 2009). Guidance is provided in EFSA (2009) on how to refine PD, however to assist in this refinement step, HSE has produced a workbook to aid the calculation of proportion of different food types in the bird and mammal diet. The workbook contains a spreadsheet and instructions page. It is strongly recommended that you read the instructions page before using the spreadsheet. It is also strongly recommended that the guidance document is read prior to using this spreadsheet.


Over the past few years PSD (now HSE)/Defra has sponsored research on the exposure of birds and mammals to pesticides. Research has also been sponsored on the effects of pesticides on birds and mammals to solid formulations. This work has been published in a range of publications.


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Updated 2024-04-26