Oxidative damages to DNA by indoor PM10s: Their relationships with trace element compositions

Plasmid DNA assay and ICP-MS analysis were conducted in order to investigate the bioreactivity of inhalable particles (PM10) and the relationship between bioreactivity and trace element compositions of PM10 in Beijing air. A total of four PM10 samples were carefully selected to represent the indoor and corresponding outdoor environments: one from urban smoker's home, two from non-smoker's homes, and the other from the outdoor. In general, the oxidative damage by indoor PM10 was slightly higher than that of outdoor. Among the four sets of samples, the PM10 from the smoker's home had a lowest TD50 (toxic dose of PM10 causing 50% DNA to be damaged), being 100 μg·mL-1, suggesting the highest bioreactivity. The heavy metals are believed to be the main reason for oxidative damage to plasmid DNA. The ICP-MS analysis combined with the DNA assay showed that the water-soluble zinc levels had better relationship with TD50 values than other elements, implying that water-soluble zinc might play an important role in the damage of DNA. It is concluded that the PM10 in smoker's home had the highest level of water-soluble zinc as well as the lowest TD50 (highest bioreactivity). Iron is considered to be one of the most bioreactive elements, but it will cause little damage to plasmid DNA, probably because iron is mainly in water-insoluble state in Beijing PM10.