Principle

For this method an existing risk assessment for soil organisms, conducted in a reference 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 reference 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 reference country.

Bridging can only be done for products containing the same active ingredient (technical material).

Data required

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

• The existing soil risk assessment report from the reference 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 the label of the pesticide to be registered.
• If the soil organisms species in the two countries are not the same: toxicity data for the species present in the local situation (LC₅₀, ECx, NOEC (mg/kg soil), if available).

Procedure

The general guidance for bridging of pesticide risk assessments provides a step-by-step procedure for this approach.

In this section, only specific aspects for the bridging of risk assessments for soil organisms are discussed.

Step 1.    Compile the data for the local case under review – See general guidance.

Step 2.    Find a reference risk assessment – See general guidance.

Step 3.    Make a case description – See general guidance.

The Assessment Summary Table for bridging of a risk assessment for soil organisms can be used to structure the case description.

Step 4. Compare the pesticide products.

In addition to the general guidance:

For the risk assessments for soil organisms, the following formulation types may be considered similar from the point of view of risks:

• All formulations applied as sprays (e.g. EC, SC, WP, WG, etc.)
  However, note that EC formulations contain significant quantities of organic solvents and/or surfactants and these may increase the toxicity of the product to soil organisms. Special attention for bridging an EC formulation to other sprayed formulations may therefore be required.
• All formulations incorporated into the soil (e.g. GR, liquid formulations injected directly into the soil), except seed treatments.
• All formulations used to treat seeds, including pre-treated seeds.

Step 5. Compare the hazards.

In addition to the general guidance, the following question may need to be addressed:

Are there important groups of soil organisms present in the local situation (e.g. essential for degradation of organic matter, or representing a large fraction of soil biomass) which are known to be more sensitive to this pesticide (or pesticides in general) than the organisms included in the reference risk assessment. Information may be available from toxicity tests with such organisms provided in the dossier or from the scientific literature. If important more sensitive organisms are present in the soil, the hazard identified in the reference risk assessment may underestimate the hazard in the local situation. In such a case, an extra assessment factor may need to be taken into account in Step 9 (comparing risks).

Step 6. Compare the exposures.

In addition to the general guidance, the following questions may need to be addressed:

Application rate and frequency may differ between the reference assessment and the proposed use of the pesticide. If this is the case, such differences should be quantified.

Differences in crop type and stage between the reference and the local risk assessment may influence exposure of soil organisms to a great extent. Pesticides applied as a spray to a closed crop canopy will result in much less exposure of the soil than a product sprayed early in the growing season when plants are still small and widely spaced. Also, pesticides applied directly to the soil (sprayed or incorporated) tend to result in higher exposure of soil organisms than products sprayed at the same application rate to a dense crop.
Furthermore, pesticides applied in row treatments tend to contaminate a smaller surface of the soil than products applied as full cover treatments. And for seed treatments, a closer sowing spacing will generally result in a higher exposure level of soil organisms.

Differences in crop structure and mode of application between the reference assessment and the local situation can therefore influence exposure of soil organisms. Whenever possible, such differences should be approximately quantified (e,g. by comparing crop interception factors) or, if not possible, it should be evaluated whether exposure of soil organisms in the local situation is likely higher or lower than in the reference assessment.
Exposure of soil organisms in the reference risk assessment will often have been estimated using an exposure model. These models use specific parameters to estimate exposure, such as application rate, soil depth, soil density, crop interception, and half-life of the pesticide in case of multiple applications and persistent pesticides. When bridging a reference risk assessment that used an exposure model, the model scenario and parameters should be compared with the local situation and it should be evaluated whether exposure in the model is likely to be higher, lower or similar to the proposed use of the pesticide product in the local situation.

Step 7. Compare risk mitigation measures – See general guidance.

Step 8. Decide whether bridging is possible – See general guidance.

Interpretation of the outcome

The outcome of the bridging assessment is summarized in Steps 9 and 10 of the guidance.

Step 9. Assess whether the risk for soil organisms in the local situation is similar, lower or higher than in the reference assessment.

Step 10. Judge whether the risk for soil organisms in the local situation can be considered acceptable.