[Oxidative Capacity of the PM₁₀ and PM_2.5 in Beijing During 2014 APEC]

In order to evaluate the effect of the joint air pollution prevention and control program on the toxicity of the airborne particles in Beijing during the APEC conference, we collected the PM₁₀ and PM_2.5 (particulate matter with aerodynamic diameters of less than 10 μm and 2.5 μm respectively) from October to December in the urban district of Beijing, and analyzed the oxidative capacity of the particles by plasmid scission assay. The results indicated that the oxidative capacity of PM₁₀ was higher than that of PM_2.5 during the APEC conference, and that the damage rate of supercoiled DNA by the samples increased with their experimental dose levels. The TD30 (toxic dose of PM causing 30% of plasmid DNA damage, unit: μg·mL^-1) was used to indicate the oxidative capacity and the lower TD30 values indicated higher oxidative capacity. The TD30 values of the PM samples before, during, and after APEC conference displayed a descending order of during APEC (November) >before APEC (October) >after APEC (December), which indicated a decreasing order of the PM oxidative capacity of after APEC (November) >before APEC (October) >during APEC. The TI (toxic index) was further introduced to represent the human exposure risk of particles, which was represented by the product of the mass concentration of PM (μg·m^-3) and the DNA damage percentages under the PM dose of 250 μg·mL^-1 (%). Compared with the TI values of previous years, the TI value of the 2014 APEC PM was lower than that of 2004, but higher than that of the 2008 Olypic Games, suggesting that the exposure risk of airborne particles decreased obviously with the increase of policy control strength.