Effect of chemical composition on the induction of DNA damage by urban airborne particulate matter

Airborne particulate matter (PM) contains a large number of genotoxic substances capable of endangering human health. In the present study, we have investigated the ability of chemically characterized water-soluble and organic-soluble fractions of two particle sizes (PM_2.5 and PM ₁₀) from different regions of Mexico City to induce DNA damage in a human lung epithelial cell line. We also evaluated associations between the physicochemical parameters of the PM and its genotoxicity. The airborne particulate samples were collected from four regions of the city; a HiVol air sampler was used to collect PM₁₀ on glass fiber filters and a tapered element oscillating system coupled to an automatic cartridge collection unit was used to collect PM_2.5 on teflon filters. PM mass was determined by gravimetric analysis of the filters. Filters containing PM_2.5 and one section of each PM₁₀ filter were agitated either with deionized water to extract water-soluble compound, or with dichloromethane to prepare organic-soluble compounds. The chemical composition of the extracts was determined by ion and gas chromatography and atomic adsorption spectroscopy. A549 human type II alveolar epithelial cells were exposed to different concentrations of the PM_2.5 and PM₁₀ extracts, and alkaline single cell gel electraphoresis or the Comet assay was performed to measure DNA damage and repair. These analyses indicated that soluble transition metals and the organic-soluble PM fractions are crucial factors in the DNA damage induced by PM. PM composition was more important than PM mass for producing gentotoxicity. The results of this study showed that the constituents of the water-soluble PM extract are more likely to induce DNA damage than the organic compounds.