Microbial interactions and health risks of organophosphate esters and their transformation products in indoor dust

• Tri-OPEs and their transformation products (TPs) were ubiquitous in indoor dust. • TPs may arise from parent tri-OPE degradation and direct commercial use. • OPE burdens correlated with bacterial community shifts, stronger in residences. • OPE levels co-occurred with higher predicted pathogenic potential in dust. • A novel ToxPi framework integrated microbial metrics for OPE risk ranking. The health risks of organophosphate esters (OPEs) have attracted increasing attention, yet information on their occurrence, transformation, and interactions with microorganisms remains limited. In this study, dust samples from various indoor microenvironments were collected and analyzed for 17 tri-OPEs and 9 transformation products (TPs), alongside characterization of bacterial communities. Both tri-OPEs and TPs were ubiquitous, with higher concentrations in public places than in residences. TPs may originate from both the degradation of parent tri-OPEs and direct commercial applications. Proteobacteria, Actinobacteriota, and Firmicutes dominated the bacterial community, with Staphylococcus as the predominant genus and numerous potential pathogenic taxa identified. Indoor OPE exposure was significantly associated with bacterial community composition (PERMANOVA, p < 0.001), with markedly stronger genus-compound associations in residences than in public microenvironments. Functional gene predictions revealed phosphatase-mediated pathways potentially involved in OPE biotransformation. Predicted pathogenic potential indices were higher in public environments and positively correlated with OPE and TP levels ( p < 0.01). Although overall hazard quotients (HQs) indicated low non-carcinogenic risks, several TPs showed HQs and predicted receptor-binding affinities comparable to those of tri-OPEs. A ToxPi-based multi-dimensional assessment, incorporating HQs, receptor binding, physicochemical properties, and microbial associations, prioritized aryl tri-OPEs as the most concerning group, while several TPs also ranked highly, warranting further regulatory attention. This study highlights the critical role of linking chemical contamination in indoor dust with microbial characteristics for health risk assessment.