Effect of heterogeneous bioaerosols on airborne microbial transports and their eco-health impacts

Bioaerosols heterogeneously containing biological components with abiological (inorganic and organic) particles provide opportunities to carry viable microorganisms over long distances into the atmosphere, synchronously affecting human health primarily through the inhalation of both biological and abiological matter. However, these complex effects of heterogeneous particles are often not recognized owing to the aerosol variability during transport and the complex physiological responses in exposed human bodies. Bioaerosol particles including bacterial and fungal cells aggregate with abiological particles, such as minerals, salts and soot, and/or are coated with fine particles to maintain microbial viability against atmospheric stressors, such as desiccation, oxidation and UV irradiation. Some pathogens that attach to aerosol particles from natural or anthropogenic dust increase the potential risk of expanding the infectious environment. Bioaerosol components including lipopolysaccharide and β-glucan are associated with allergenic and inflammation events via membrane-transport recognition, such Toll-like receptor recognition, and cytokine pathways in the human lung tissues. Consequently, the heterogeneous properties of aerosol particles exacerbate the risk of respiratory symptoms because different allergenic pathways involving biological and abiological matter induce synchronous immune responses. Furthermore, abiological aerosol particles may cause direct or indirect injury to human tissues, which can become easily infected by pathogens and activate the allergy-cytokine pathway. This review highlights the complex properties of heterogeneous aerosols in relation to atmospheric transport processes and their synchronous impacts on human health.