Comprehensive risk assessment for five SDHI fungicides with AhR agonistic activity to aquatic ecosystems

Succinate dehydrogenase inhibitor (SDHI) fungicides are widely used in agriculture to control rice sheath blight and various crop diseases, and have become increasingly prevalent in ecosystems due to expanded agricultural applications and evolving regulatory policies. This study assessed the aquatic ecological risks of five SDHI fungicides exhibiting aryl hydrocarbon receptor (AhR) agonistic activity. Our results demonstrated that: (1) all five parent SDHI fungicides and 18.5 % of their transformation products (TPs) demonstrated aquatic toxicity (T), with green algae exhibiting particular sensitivity; (2) 21.5 % of TPs retained AhR agonistic activity, while 9.7 % displayed strong environmental persistence (P) and mobility (M) characteristics; and (3) 89.7 % of PMT-classified TPs maintained strong binding affinity to SDH proteins across multiple aquatic species. Notably, halogen-containing TPs derived from flutolanil and benodanil constituted the predominant source of PMT-type TPs. Furthermore, our analysis revealed that several SDHI-derived TPs are aromatic amines, suggesting these fungicides may represent a significant agricultural source of aromatic amine pollutants. These findings provide critical insights into the environmental fate and ecological impacts of SDHI fungicides and highlight the potential aquatic risks posed by both parent compounds and TPs, offering valuable scientific support for developing evidence-based pollution control strategies.