Environmental Health Perspectives 105, Supplement 5, September 1997

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Free Radical Activity of PM 10 : Iron-mediated Generation of Hydroxyl Radicals

Kenneth Donaldson, 1 David M. Brown, 1 Colin Mitchell, 1 Miglena Dineva, 1 Paul H. Beswick, 1 Peter Gilmour, 1 and William MacNee 2

1 Department of Biological Sciences, Napier University, Edinburgh, United Kingdom
2 Unit of Respiratory Medicine, Department of Medicine, University of Edinburgh Royal Infirmary, Edinburgh, United Kingdom

Abstract
The purpose of this study was to test the hypothesis that particulate matterLess than or = to10 µm in aerodynamic diameter (PM 10 ) particles have the ability to generate free radical activity at their surface. We collected PM 10 filters 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 PM 10 particles did cause damage to the DNA that was mediated by hydroxyl radicals, as shown by inhibition of the injury with mannitol. The PM 10 -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 PM 10 filters confirmed the presence of large amounts of iron and leaching studies confirmed that the PM 10 samples 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 PM 10 to 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. -- Environ Health Perspect 105(Suppl 5):1285-1289 (1997)

Key words : PM 10 , air pollution, free radical, oxidative stress, environmental lung disease

This paper is based on a presentation at The Sixth International Meeting on the Toxicology of Natural and Man-Made Fibrous and Non-Fibrous Particles held 15-18 September 1996 in Lake Placid, New York. Manuscript received at EHP 27 March 1997; accepted 7 July 1997.

Address correspondence to Professor K. Donaldson, Department of Biological Sciences, Napier University, 10 Colinton Road, Edinburgh, EH10 5DT, UK. Telephone: 0131 455 2262. Fax: 0131 455 2291. E-mail: k.donaldson@napier.ac.uk

Abbreviations used: COPD, chronic obstructive pulmonary disease; 2,3 DHBA, 2,3 dihydroxybenzoic acid; DSF-B, desferrioxamine-B; EDXA, energy dispersive X-ray analyzer; HPLC, high-performance liquid chromatography; PM 10 , particulate matterLess than or = to10 µm in aerodynamic diameter; SPM, suspended particulate matter.

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Last Update: November 21, 1997