Step 4. Compare the pesticide products
Bridging can only be done for pesticide products which contain the same active ingredient (a.i.) in the reference assessment and in the local situation; such a.i.’s have the same common name and/or CAS number, and have the same isomer ratio where relevant.
Pesticide products are then compared according to three parameters:
i. The similarity of the active ingredient, including its impurities
ii. The concentration of the active ingredient and any relevant impurities
iii. The type and composition of the formulation
i. Active ingredient and its impurities
Ideally, the active ingredients are identical, i.e. manufactured by the same company through the same manufacturing process, as this will normally ensure that the relevant impurities (i.e. impurities of toxicological relevance) are the same. As a result, the hazards of the two active ingredients will be the same.
Alternatively, the active ingredients can also be equivalent, which means that the relevant impurities (and associated hazards) will not differ significantly.
Finally, if the active ingredients have not been shown to be equivalent, but there is sufficient information to justify that the hazard of the a.i. is not significantly different for the local product than for the reference product, bridging can still be conducted.
ii. Active ingredient concentration
If the concentrations of the active ingredient(s) in the two products that are bridged are the same, bridging is facilitated.
However, it should be emphasized that in many cases, the concentration of the a.i. in the formulation does not significantly affect risk (e.g. for dietary risk, surface water risks, soil organisms or pollinators, it is the application rate that is a key risk factor, not the pesticide concentration in the product).
In some cases, the a.i. concentration in the product may be important for bridging; e.g. for operator risk assessment, when mixing and loading is done using the concentrated product. If this is the case, acceptable variations in the a.i. concentration are indicated in Table 1. If differences in a.i. are within the ranges of Table 1, the hazard of the product is not expected to be significantly affected.
Table 1. Indicative acceptable variations in hazardous constituents of a pesticide product | |
Concentration range (C) of the hazardous constituent | Acceptable variation in concentration |
C <= 0.5 % | 100 % |
0.5 < C <= 1.0 % | 50 % |
1.0 < C <= 2.5 % | 30 % |
2.5 < C <= 10 % | 20 % |
10 < C <= 25 % | 10 % |
25 < C <= 100 % | 5 % |
Sources: EU (2008) & EC (2012) | |
Relevant impurities in the active ingredient should always be below the maximum limits set in manufacturing specifications, both for the local and the reference product. International pesticide specifications are published by FAO & WHO.
iii. Formulation type and composition
Many differences in formulation type have limited or no influence on the risk of the product. This will need to be assessed on a case by case basis, depending on the specific risk being evaluated.
The following formulation types can generally be considered similar for bridging a risk assessment:
- Dietary risk assessment: formulation types which are diluted in water prior to application including EC, WP, WG, SC, SL. Experience demonstrates that these formulations lead to similar residues.
- Occupational and bystander risks: i) all solid formulations applied as a spray; ii) all liquid formulations applied as a spray; iii.) formulations applied as granules.
- Environmental risk assessment: i) all formulations applied as sprays; ii) formulations applied as granules; iii) formulations for seed treatments
Other cases exist where different formulations can be bridged without a likely significant effect on the risk.
Care has to be taken when different formulation types clearly may pose different risks, in particular when low risk formulations are used in the reference country (e.g. microencapsulated products, water-soluble bags) but more conventional but higher risk formulations in the local situation.
Even though formulation types may be similar, the formulation composition may still contain different co-formulants. Generally, co-formulants are considered confidential business information, and are not publicly specified, except when they are hazardous (i.e. co-formulants that trigger a hazard classification). Therefore, the product evaluated for the local situation should not contain new hazardous co-formulants when compared to the reference product. Furthermore, when the same co-formulants are found in the local and reference products, differences in concentrations should not exceed the limits of Table 1.
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