Occupational exposure to printer toner-emitted nanoparticles at printing facilities influences air and airway microbiomes

Workplace exposure to printer toner-emitted nanoparticles at commercial printing facilities poses respiratory health risks to workers on the printing floor, however, its impact on environmental and airway microbiomes and how this relates to worker health remains unknown. To investigate this, we prospectively evaluated five printing centres in Singapore, collecting air samples from office areas and printing floors and airway specimens from workers stationed in office or printing floor areas. All specimens were subjected to targeted amplicon sequencing to determine bacteriome and mycobiome profiles. Relationships between nanoparticle exposure levels, air and airway microbiomes were assessed. We reveal that nanoparticle exposure at printing facilities was significantly associated with shifts in air microbiome profiles in high-exposure printing areas relative to low-exposure office areas. Microbiome correlates of indoor air chemical exposures, mainly polycyclic aromatic hydrocarbons (PAHs) and trace elements, were identified. Lung function and airway microbiomes were influenced by nanoparticle exposure where printing floor workers demonstrate reduced lung function, independent of exposure level, with airway microbiomes characterized by enrichment of Chryseobacterium, Porphyromonas and Candida. Assessment of potential air-airway microbial crossover at each site, accounting for nanoparticle exposure levels, reveals significant increases in bacterial but not fungal crossover in printing floor workers. Taken together, this study demonstrates altered environmental and airway microbiomes at commercial printing facilities and in printing floor workers. Further research is needed to assess the long-term health impacts of such exposure including the potential for microbial profiling in printing facility design and operation.