Pesticide Registration Toolkit

Bridging of an existing risk assessment for honeybees

Relevant documents
Guidance on bridging of pesticide risk assessments


For this method an existing honeybee risk assessment, conducted in another country, is “bridged” to the local situation. The existing risk assessment is reviewed and a comparison is made between pesticide use situations described for the other country with the local situation. On the basis of this comparison, the registrar then evaluates whether the risk in the local situation is similar, higher or lower than in the other country.

This bridging of risks is based on the principle that the toxicity of a pesticide to honeybees is similar, irrespective of the honeybee species (the main domesticated honeybee species are Apis mellifera – including the Africanized honeybee – and Apis cerana
Differences in pesticide risks for honeybees are then mainly determined by differences in the level of exposure of the bees. The bridging assessment therefore consists of a qualification, and where possible quantification, of the difference in exposure between the situation for which a reliable risk assessment exists and the local situation for the pesticide under review.

Bridging can only be done for products containing the same active ingredient (technical material).
Furthermore, the bridging procedure described here refers specifically to honeybees (Apis spp.). Extrapolating the risk of an insecticide for honeybees to other non-Apis bees is more complicated and discussed in a separate section

Data required

The following data are generally used for bridging honeybee risk assessments.

  • The existing honeybee risk assessment report from another country.
  • Information on the proposed directions for use of the pesticide to be registered. This is generally summarized in the Good Agricultural Practice (GAP) table and/or label of the pesticide to be registered.
  • If the honeybee species in the two countries are not the same: toxicity data for the species present in the local situation (acute oral and contact LD50; acute oral brood LD50 and chronic toxicity data, if available)


  1. Obtain a reliable honeybee risk assessment from another country for the same pesticide (same a.i. and if possible the same or a similar formulation). If the applicant has not provided such an assessment, registration reviews from reputable registration authorities can be searched through the Scientific Reviews page of the Toolkit.
  2. Obtain the detailed description of the expected use conditions in your country, e.g. from the registration dossier (see “data required”, above).
  3. Make a comparison of use conditions, and relative risks, between the pesticide to be registered and the situation in the existing risk assessment. The Assessment Summary Table can be used to summarize the data.
  4. Evaluate whether the honeybee risk for the local situation for which registration is sought is likely to be similar, higher or lower than for the existing risk assessment.

Interpretation of the outcome

Because the toxicity of the pesticide is can be considered similar for domesticated honey bee species, honeybee risks can be bridged based on differences in exposure between the existing risk assessment and the local situation under review.

In principle, if the risk to honeybees in an existing assessment from another country was considered to be acceptable, and exposure levels in the local situation are likely to be similar or lower, then the risk for the local situation is also likely to be acceptable. Alternatively, if the honeybee risk in an existing assessment was considered not to be acceptable, and exposure levels in the local situation are likely to be similar or higher, then the risk for the local situation is probably also not acceptable.

In other cases, a valid extrapolation cannot be made and a local honeybee risk assessment should be carried out.

The table below shows the various possible outcomes of the bridging exercise.