From waste to workplace: Airborne microplastics and endotoxins in an indoor industrial environment

Airborne microplastics (MPs) and endotoxins are emerging occupational hazards, yet their co-occurrence in real workplaces is poorly documented. The study examined combined exposure in sludge-based fertilizer plant, where digestate handling and drying generate both polymer-rich dust and bioaerosols. Personal and stationary air samples were collected with calibrated pumps at three indoor hotspots: conveyor pipe, dryer, loading dock with an outdoor site. Microplastics were extracted in an ultra-clean laboratory and characterized by μ-FTIR imaging. Endotoxin levels were quantified by the LAL assay. Indoor air contained significantly higher MP counts (24-312 MP m −3 ) than outdoor (13 MP m −3 ), dominated by fragment-shaped particles (74%) vs fibres (26%) within the inhalable size fractions. Concentrations peaked near the sludge dryer unit and the conveyor, indicating process-related sources and resuspension of contaminated dust. Endotoxins (