Considering the Size Distribution of Elements in Particle Matter and Oxidation Potential: Association before and after Respiratory Exposure

Abstract

Oxidation potential (OP), reflecting the redox activities of particle matter (PM), is considered an optimal measure to explain the biological effects of PM exposure. However, the size resolution of the relationship between OP and chemical composition in PM, especially how the relationship changes after respiratory exposure, has not been well investigated. In this study, size-resolved indoor PM10 samples were collected from a waste recycling plant from November to December 2021 using an Anderson eight-stage cascade impactor. OP, measured by a dithiothreitol (DTT) assay (defined as OPDTT), and elements, determined by inductively coupled plasma–mass spectrometry (ICP-MS) in size-resolved PM, were determined to check their relationships and the related human exposure risk. The results indicated that compared with PM0.4 and PM0.4–2.1, PM2.1–10 contributed the most to total OPDTT and its bound elements contributed the most to potential health risks, both before and after respiratory exposure. The association between OPDTT and the elements varied with PM size. Pearson correlation analysis showed that the PM0.4- and PM0.4–2.1-bound elements were moderate-to-strongly positively correlated with OPvDTT (r: 0.60–0.90). No significant correlation or dose–response relationship was found in PM2.1–10. After respiratory exposure, several PM0.4- and PM0.4–2.1-bound elements had a moderate-to-strongly positive correlation with deposition fluxes of OP (defined as OPFlux) (0.69–0.90). A generalized linear model analysis showed that the interquartile range (IQR) increase in the PM-bound elements (ng h−1) was associated with a 41.7–58.1% increase in OPFlux. Our study is a special case that enriches the knowledge of the association between OPDTT and the chemical composition of PM of different sizes, especially after respiratory exposure, but the generalizability of the findings to other settings or types of PM may be limited. The associations among OPDTT, other chemical compositions of PM, and human exposure risk merit further research.