Chlorothalonil Metabolites: Relevant or Not?

As a reminder: The fungicide chorothalonil was classified as probably carcinogenic (Category 1B) by the Federal Food Safety and Veterinary Office (FSVO) in December 2019. The sale and use of chlorothalonil-containing pesticides was banned on January 1, 2020, which automatically results in the relevance classification of all chlorothalonil metabolites and thus a maximum content of 0.1 µg / l in accordance with the ordinance on drinking water and water in publicly accessible baths and shower facilities (TBDV) Had a consequence. Since this maximum level has been exceeded at many measuring points in Switzerland due to the metabolites R417888 and R471811, drinking water suppliers were asked to take immediate measures and meet the legal requirements within a specified period. The reassessment is contradictory in that the FSVO, with the participation of the FOAG (Federal Office for Agriculture) as a specialist authority, classified four metabolites (including the two above-mentioned) as irrelevant in its report of December 3, 2019.

In January 2020, Syngenta Agro AG appealed to the Federal Administrative Court against the ban on chlorothalonil. The proceedings are still pending, but two interim rulings have already been issued in which Syngenta Agro AG's applications for precautionary measures have been approved. In the second interim ruling, the FSVO is required not to designate four metabolites of chlorothalonil, including R417888 and R471811, as toxicologically relevant for the time being (this would once again result in a high maximum level of 10 µg / l). According to a media release from the Federal Administrative Court of February 18, 2021, it will only be necessary to assess in the main decision which classification with regard to carcinogenicity (category 2 or 1B) is to be assumed and whether all metabolites are automatically considered relevant with a possible classification in category B1, and which maximum drinking water levels (10 µg / l or 0.1 µg / l) are applicable.

Due to the pending proceedings, Labor Veritas AG has decided to suspend the conformity assessment of water samples in accordance with the TBDV in connection with the chlorothalonil metabolites until the legal situation has been clarified. The following note therefore appears on our test reports: "Due to the currently unclear legal situation with regard to the applicable maximum values for the metabolites of chlorothalonil, the samples are no longer evaluated for conformity". In our Spotlight No. 34 from May 2020 , all metabolites of chlorothalonil are described as relevant due to the initial situation at the time. This statement should be treated with caution for the time being. This spotlight will not be updated for the time being, especially because the statements made in it could become valid again.