Succinate dehydrogenase inhibitors (SDHIs) are active substances used in fungicidal products to control certain fungi and moulds affecting crops. SDHIs prevent their development by blocking an enzyme involved in cell respiration: succinate dehydrogenase (SDH). Eleven active substances from this class are currently used in plant protection products authorised in France.
In an article published in the press, a group of scientists warned of the potential risks associated with these SDHI substances. In accordance with its principles for dealing with alerts, the Agency therefore set up a dedicated group of independent experts to examine the hypotheses put forward by these scientists and determine whether they constituted a health alert. In particular, this expert group interviewed the researchers raising the alert in order to obtain the information they possessed. The Agency also promptly forwarded this information to all the European competent authorities.
The experts analysed data from the active substance assessment dossiers produced in accordance with the European regulations and data on the human health risks associated with each use of the products, along with mammalian toxicity and carcinogenicity, for all of the pathways and mechanisms of action that may be responsible for this toxicity (genotoxicity, epigenetics, mitotoxicity, etc.).
Data from the international scientific literature and databases, and on surveillance (mainly on environmental and food contamination), vigilance and control were also studied by the ANSES expert group.
This work did not provide any evidence to support the existence of an alert for human health and the environment related to agricultural uses of these fungicides that justified amending or withdrawing the marketing authorisations.
Indeed, the level of total dietary exposure is low in relation to the current toxicological thresholds, and the maximum residue limits for these active substances are only exceeded in exceptional cases. Furthermore, these substances are rapidly metabolised and eliminated. Lastly, with regard to the sources consulted, the experts did not identify any data suggesting an increased incidence of specific cancers associated with SDH-deficiency in humans not carrying a mutation (in exposed workers, for example), despite the fact that in some cases these SDHI compounds have been on the market for a long time, nor any data suggesting an impact on environmental organisms.
Nevertheless, ANSES does not regard the issue as closed. As part of its phytopharmacovigilance scheme, therefore, ANSES is already pursuing investigations to determine levels of internal exposure to SDHIs (the quantity of substance found in the body) and to conduct further epidemiological research, particularly among farmers.
The experts also recommend further studies on SDHIs and on methodologies for assessing the risks associated with the uses of plant protection products, in which the Agency is already involved.