Structure-activity relationship (SAR) and quantitative structure-activity relationship (QSAR) models, collectively referred to as (Q)SARs, are mathematical models that can be used to predict the properties of compounds based on knowledge of their chemical structure. The basic principle of (Q)SARs is that chemical substances that are structurally similar will have similar properties, which could include physicochemical, biological, toxicological and environmental-fate properties.

In the context of plant protection products under Regulation (EC) No 1107/2009 and the Biocidal Products Regulation (BPR) Regulation (EU) 528/2012, (Q)SARs are mainly used in the assessment of the equivalence of technical materials. The level of hazard posed for health and environmental protection must be comparable for different sources of technical material.

A two-tiered approach is employed to assess technical equivalence: if equivalence cannot be established on the basis of the Tier I data, further mammalian toxicity/ecotoxicity consideration is necessary which will form the requirements of Tier II. In all cases of new/increased levels of impurities, a (Q)SAR analysis should be conducted in order to predict the toxicity of the impurity based on its chemical structure, if a reliable prediction is possible and can be supported scientifically. The (Q)SAR assessment for the impurity must be conducted alongside the active substance in order to consider whether any structural alerts are also present in the active substance.

(Q)SARs used should be well documented in terms of their applicability domain, validated at the EU level and suitable for predicting the endpoints of interest. While commercially available models are available for toxicity (e.g. DEREK, TOPKAT), the use of SAR and QSAR approaches for ecotoxicity is more limited by the lower availability of reliable models for the whole spectrum of taxonomic groups occurring in the environment.

Kerona provides a range of services for assessment of the equivalence of technical materials under Regulation 1107/2009 and the BPR, including the following services for (Q)SAR assessment:

  • Assessment of the need for the (Q)SAR as part of the Tier II requirements for technical equivalence
  • Conducting and interpreting the (Q)SAR assessment for both the impurity and the active substance
  • (Q)SAR assessments for toxicity end-points (e.g. using DEREK)
  • (Q)SAR assessments for ecotoxicity end-points (e.g. using OECD toolbox, ECOSAR)
  • Guidance on options for next steps in the case of a positive alert from the (Q)SAR assessment

If you have any queries relating to (Q)SARs and our services for plant protection and biocides, please send an email to or contact the team on +353 1 849 5284.