Pesticide Registration Toolkit

Bridging of existing worker risk assessment

Relevant documents
Guidance on bridging of pesticide risk assessments
Assessment summary table Bridging an existing worker risk assessment icon


In this assessment an existing worker 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 situation 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 extrapolation is based on the principle that the human toxicity of a pesticide is relatively similar, irrespective of the country or situation in which the pesticide is being used. Differences in worker risk are then determined mainly by differences in the level of exposure. The assessment therefore provides a qualification, and where possible quantification, of the difference in exposure between a situation for which a thorough and reliable risk assessment exists, and the situation for the pesticide under review.
Bridging can only be done for products containing the same active ingredient (technical material). If the manufacturing source of the technical materials is different, whenever possible, equivalence between the two technical materials should be established.
The more similar the work situation (e.g. application rate & frequency, work location (indoor/outdoor), crop, task, PPE) the easier bridging is likely to be. When the differences between the work situations are greater, bridging may be more complicated or even impossible.
Note that the assumption that human toxicity of the pesticide is similar, irrespective of the country in which it is used, may not always be true. In certain cases, persons may be more, or less, susceptible to adverse effects caused by pesticides; see the section on General hazard assessment for more information.

Data required

The following data are generally used for bridging worker risk assessments.
  • The existing worker 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.
  • The Acceptable Operator Exposure Level (AOEL).
  • The crop in which the work is being carried out and the tasks the worker is expected to conduct.
  • Information on work practices for the situation under review (e.g. work rate, number of work days per year, re-entry interval).
  • Type of personal protective equipment (PPE) available/required, and possible other protective measures.


  1. Obtain a reliable worker risk assessment(s) 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 Assessment summary table Bridging an existing worker risk assessment icon can be used to summarize the data.
  4. Evaluate whether the risk of occupational exposure for the pesticide under review is likely to be similar, higher or lower than for the existing risk assessment.

Interpretation of the outcome

If one can assume that the Acceptable Operator Exposure Level (AOEL) for the pesticide is basically the same globally, it may be possible to bridge worker risk based on differences in exposure between the existing risk assessment and the situation under review.
In principle, if the occupational risk in an existing assessment was considered to be acceptable, and exposure levels in the situation under review are likely to be similar or lower, then the risk for the situation under review is also acceptable. Alternatively, if the occupational risk in an existing assessment was considered not to be acceptable, and exposure levels in the situation under review are likely to be similar or higher, then the risk for the situation under review is also not acceptable.
In other cases, a valid extrapolation cannot be made and a local risk assessment should be carried out using an exposure model and/or exposure measurements. 
The table below shows the various possible outcomes of the bridging exercise.