The cytotoxicity and genotoxicity of PM₂.₅ during a snowfall event in different functional areas of a megacity

Abstract

Atmospheric fine particulate matter (PM₂.₅) can harm human health, but the chemical composition and toxicity of PM₂.₅ pollution might vary with weather conditions. In order to investigate the impacts of snowfall weather on aerosol characteristics and toxicity by changing particle sources and components, the daily PM₂.₅ samples were collected before, during, and after a snowfall event in urban, industrial, suburban, and rural areas of Nanjing city in eastern China, for both chemical composition analysis and cytotoxicity tests. After 24 h exposure to these PM₂.₅, the cell activity, oxidative stress indicators and inflammatory factor expression levels of human lung epithelial cells A549 were measured by ELISA, and DNA damage was determined by comet assay. Although the concentrations of PM₂.₅ in the air were reduced during snowfall, they posed stronger cytotoxicity, genetic toxicity and inflammatory responses to A549 cells. Related to the elevated mass concentrations of some components accumulated in PM₂.₅ during snowfall, As, Co, Cr, Sr, V, water-soluble Na⁺ and Ca²⁺ showed positive correlations with toxicity indicators. Therefore, snowfall will clean air by deposition, but also make the PM₂.₅ components remaining in air mostly anthropogenic by covering ground soil/dust, thus increase the particle's mass-based cytotoxicity and their health risks still cannot be ignored, such as the heavy metals and water-soluble ions from automobile exhaust and coal combustion.