The European Food Safety Authority (EFSA) recently published its preliminary peer review findings for the active substance prothioconazole. This review was conducted in accordance with EU Regulations (EU) No 844/2012 and its amendment No 2018/1659, primarily referencing risk assessment reports submitted by Poland (which took over from the UK post-Brexit) and France. The assessment focused on typical application methods of prothioconazole on cereal crops such as barley, wheat, oats, spelt, rye, and triticale, including foliar spray and seed treatment.

Key Change: Active Substance Specification Updated

The review has revised the reference specification for prothioconazole, adding two new relevant impurities that require control. Specific indicators have been updated.

Toxicology and Consumer Safety Assessment

Regarding prothioconazole itself, no significant toxicological concerns have been identified. The consumer exposure to its main metabolite, M04 (desthio-prothioconazole), is well below 15% of the toxicological reference values (TRVs), indicating an acceptable risk level.

However, the review highlighted a key uncertainty: insufficient data exist to rule out the potential genotoxicity of metabolites M15, M17, M33, and M35. Consequently, the current consumer dietary risk assessment is classified as provisional, with a final conclusion pending clarification of these concerns.

The assessment of triazole derivative metabolites (TDMs) indicated that exposure levels from prothioconazole were below the thresholds established in previous specific TDM assessments.

Efficacy Performance

As a fungicide, prothioconazole demonstrated adequate control of target diseases in the declared representative crops such as barley and wheat.

Environmental and Ecotoxicological Considerations

The review identified several environmental risks:

The use of 100 g/L prothioconazole FS for winter cereal seed treatment may pose a high long-term risk to birds and mammals.

The metabolite M04, resulting from the spray application of a mixed formulation of 150 g/L prothioconazole + 75 g/L bixafen EC on winter cereals, presents a high long-term risk to aquatic organisms.

Furthermore, because the representative co-formulation "Aviator EC 225" contains another active substance, bixafen, and no data on its combined exposure and risk to soil, surface water, and sediment were provided for this assessment, this part of the evaluation could not be fully completed.

Endocrine Disrupting Properties Review

Based on available data, EFSA's preliminary conclusion is that prothioconazole does not meet the criteria for human and non-target organism endocrine disruptors as defined by EU Regulation (EU) 2018/605. While conclusions regarding the thyroid modality (T-modality) in non-mammalian organisms still require further confirmation, current evidence suggests it is unlikely to be an endocrine disruptor.

Preliminary Conclusions and Outlook

EFSA's comprehensive assessment indicates that, under the current framework, prothioconazole does not pose a significant concern to human health. However, its potential risks to the ecological environment, particularly to birds, mammals, and aquatic organisms, require serious attention. The review also clearly pointed out several data gaps, such as the confirmation of genotoxicity for certain metabolites and the cumulative risk assessment of bixafen in co-formulations.

Whether prothioconazole ultimately receives a renewal of its registration will depend on how the European Commission and the risk management authorities of the Member States weigh these scientific findings and potentially consider implementing appropriate risk mitigation measures.