Reduced <em>in vitro</em> toxicity of fine particulate matter collected during the 2008 summer Olympic Games in Beijing: The roles of chemical and biological components.

Beijing has implemented systematic air pollution control legislation to reduce particulate emissions and improve air quality during the 2008 Summer Olympics, but whether the toxicity of fine fraction of particles (PM2.5) would be changed remains unclear. In present study we compared in vitro biological responses of PM2.5 collected before and during the Olympics and tried to reveal possible correlations between its chemical components and toxicological mechanism(s). We measured cytotoxicity, cytokines/chemokines, and related gene expressions in murine alveolar macrophages, MH-S, after treated with 20PM2.5 samples. Significant, dose-dependent effects on cell viability, cytokine/chemokine release and mRNA expressions were observed. The cytotoxicity caused at equal mass concentration of PM2.5 was notably reduced (p&lt;0.05) by control measures, and significant association was found for viability and elemental zinc in PM2.5. Endotoxin content in PM2.5 correlated with all of the eight detected cytokines/chemokines; elemental and organic carbon correlated with four; chromium and arsenic correlated with six and three, respectively; iron and barium showed associations with two; nickel, magnesium, potassium, and calcium showed associations with one. PM2.5 toxicity in Beijing was substantially dependent on its chemical components, and lowering the levels of specific components in PM2.5 during the 2008 Olympics resulted in reduced biological responses