Is the oxidative potential of components of fine particulate matter surface-mediated?

Redox-active substances in fine particulate matter (PM) contribute to inhalation health risks through their potential to generate reactive oxygen species in epithelial lung lining fluid (ELF). The ELF's air-liquid interface (ALI) can play an important role in the phase transfer and multi-phase reactions of redox-active PM constituents. We investigated the influence of interfacial processes and properties by scrubbing of coated nano-particles with simulated ELF in a nebulizing mist chamber. Weakly water-soluble redox-active organics abundant in ambient fine PM were reproducibly loaded into ELF via ALI mixing. The resulting oxidative potential (OP) of selected quinones and other PAH derivatives were found to exceed the OP resulting from bulk mixing of the same amounts of redox-active substances and ELF. Our results indicate that the OP of PM components depends not only on the PM substance properties but also on the ELF interface properties and uptake mechanisms. OP measurements based on bulk mixing of phases may not represent the effective OP in the human lung.

Automated summary

The redox-active substances in fine particulate matter (PM) can generate reactive oxygen species in epithelial lung lining fluid (ELF), which pose inhalation health risks. The air-liquid interface (ALI) in the ELF plays a crucial role in the phase transfer and multi-phase reactions of redox-active PM constituents. Our study investigated the influence of interfacial processes and properties on the oxidative potential (OP) of PM components and found that the OP can exceed that resulting from bulk mixing, suggesting that OP measurements based on bulk mixing may not accurately represent the effective OP in the human lung.