Free Radical Activity of PM10: Iron-Mediated Generation of Hydroxyl Radicals

• Published in: Environmental health perspectives 1997-09, Vol.105 (suppl 5), p.1285-1289
• Main Authors: Donaldson, Kenneth, Brown, David M., Mitchell, Colin, Dineva, Miglena, Beswick, Paul H., Gilmour, Peter, MacNee, William
• Format: Article
• Language: English
• Subjects: Air Pollutants - toxicity; Air pollution; Antidotes - pharmacology; Asbestos; Chemical suspensions; Chromatography, High Pressure Liquid; Deferoxamine - pharmacology; Electron Probe Microanalysis; Free radicals; Hydrogen-Ion Concentration; Hydroxyl Radical - metabolism; Hydroxyl radicals; Iron - physiology; Lungs; Microscopy, Electron, Scanning; Oxidative stress; Particle Size; Particulate matter; Plasmids; Plasmids - drug effects; Plasmids - genetics; Spectrometry, X-Ray Emission
• ISSN: 0091-6765; 1552-9924
• DOI: 10.1289/ehp.97105s51285

The purpose of this study was to test the hypothesis that particulate matter ≤ 10 μm in aerodynamic diameter ( PM10) particles have the ability to generate free radical activity at their surface. We collected PM10filters from the Edinburgh, United Kingdom, Enhanced Urban Network sampling site, removed particles from the filter, and tested their ability to cause free radical damage to supercoiled plasmid DNA. We found that the PM10particles did cause damage to the DNA that was mediated by hydroxyl radicals, as shown by inhibition of the injury with mannitol. The PM10-associated hydroxyl radical activity was confirmed using a high-performance liquid chromatography-based assay to measure the hydroxyl radical adduct of salicylic acid. Desferrioxamine abolished the hydroxyl radical-mediated injury, which suggests that iron was involved. Analysis of PM10filters confirmed the presence of large amounts of iron and leaching studies confirmed that the PM10samples could release substantial amounts of Fe(III) and lesser amounts of Fe(II). To investigate the size of the particles involved in the hydroxyl radical injury, we centrifuged the suspension of PM10to clarity, tested the clear supernatant, and found that it had all of the suspension activity. We conclude, therefore, that the free radical activity is derived either from a fraction that is not centrifugeable on a bench centrifuge, or that the radical generating system is released into solution.