Study on Microorganisms─Particulate Air Pollutants from Hospital Wastewater: Occurrence, Respiratory Toxicity, and Risk Impact

Airborne microbes and particulate matter (PM) from hospital wastewater pose significant transmission risks, yet their combined toxicity─specifically how microbes modulate PM toxicity─remains unclear. This study characterized airborne microbes and PM at a hospital sewage treatment center (HSTC) and assessed their coexposure effects on pulmonary toxicity in a mouse model. At HSTC, elevated concentrations of bacteria (246 CFU/m3) and PM (306.93 μg/m3), along with a higher annual proportion of PM2.5 (48.7% vs 38.0%), indicated increased inhalation risk. Core airborne genera─Ochrobactrum, Brevundimonas, and Pseudomonas─are opportunistic pathogens. Compared to PM exposure alone, coexposure with microbes aggravated acute lung injury at 24 h, manifesting as more severe bronchial hemorrhage, granulocyte infiltration, and alveolar wall thickening. The relative abundance of pulmonary pathogens, particularly Staphylococcus and Pseudomonas, increased in a dose-dependent manner. By 72 h, PM-associated biocomponents generally raised the pathogenic potential and reduced the diversity of the lung microbiota (e.g., Shannon index decreased by an average of 1.70), exacerbating pulmonary dysbiosis and infection risk. These findings demonstrate that microorganisms in hospital-wastewater-derived bioaerosols exacerbate PM-induced respiratory toxicity. They highlight the critical interplay between microbes (particularly pathogens) and PM, underscore the necessity for relevant worker respiratory protection, and inform improved wastewater-management strategies.