Co-generated solid particles as protectants enhancing the survival of airborne bacteria and its influence on exposure assessment

• The impact of co-generated solid particles on aerosolized bacteria was investigated. • With the protection of solid particles, the recovered bacteria increased by 142 %. • Sub-micrometer solid particles exhibited greater protective effects. • The number of recovered bacteria rose with the increase of particle concentration. • Co-generated particles generated by dental procedures increased infection risk of dentists. Exposure to aerosolized bacteria poses a significant threat to human health as they can cause various respiratory infections. In dental clinics, the bacteria-laden aerosols generated from dental procedures may disperse to the dentist’s breathing zone via air and cause cross-infection. A unique feature for aerosols generated during dental procedures is that they contain solid particles. In this study, the impact of co-generated solid particles on the activity of aerosolized bacteria and its influence on exposure assessment were investigated. This study first compared the recovery of aerosolized bacteria with and without co-generated solid particles. The results showed that with co-generated solid particles, the number of recovered bacteria increased by 142 %. Then, the effects of three influencing factors were analyzed, including solid particle size, particle concentration in suspension, and relative humidity of air. Finally, the influence of co-generated solid particles on the exposure assessment in a dental clinic was numerically evaluated. The results showed that, if the impact of co-generated solid particles was not considered, the dentist’s exposure would be under-estimated by 58.6 %. This study revealed the phenomenon of co-generated solid particles acting as protectants to enhance the bacterial survival in aerosols, providing valuable insights for accurate exposure and risk assessment.