Last month the European Food Safety Authority (EFSA) published a summary of the conclusions on recurring issues in pesticide mammalian toxicology in the EFSA Journal. This was a summary of the meeting been EFSA and toxicology experts representing EU member states. Several topics were discussed, such as endocrine disruption, assessment of impurities and isomers, and use of (Q)SARs.

Of particular interest to the genetic toxicology committee was FSA’s approach to the assessment of groundwater metabolites. The guidance for assessing groundwater metabolites in the EU dates back to 2003 (Sanco/221/2000 –rev.10- final) and precedes several changes to OECD guidelines for genotoxicity testing. Essentially, it intends to guide the assessment necessary to decide whether a metabolite is ‘relevant’ or ‘non-relevant’. Relevant metabolites exceeding 0.1 µg/L (1 ppb) would not be acceptable under the EU Drinking Water Directive. Genotoxicity is one of the criteria for assessing relevance/non-relevance.

The Groundwater metabolite non-relevance guidance advises that to assess genotoxicity, a battery of genotoxicity tests should be performed: the Ames test, a mammalian gene mutation assay and in vitro chromosome aberration assay, with equivocal results followed up in vivo. EFSA pointed out that the conduct of in vitro chromosome aberration studies would not adequately assess aneugenicity and that this would be flagged as a data gap.

The data gap could be filled by conducting an in vitro micronucleus study. However, agrochemical companies potentially need to conduct large numbers of in vitro micronucleus studies to update their older data packages for the EU registration process. This presents not only a budget and planning challenge but will inevitably trigger some in vivo testing, given that in vitro studies are known to lead to misleading positive results. Some agrochemical companies have already switched to conducting in vitro micronucleus studies instead of chromosome aberration studies, despite the wording of the 2003 guidance, which is in line with updated data requirements for pesticide-active substances.

At Gentronix, we offer OECD 487-compliant in vitro micronucleus studies using either TK6 cells (with FISH addition if required) or human lymphocytes. Please contact or contact us at to discuss your needs in this area.