SUPERCOILED PLASMID DNA AS A MODEL TARGET FOR ASSESSING THE GENERATION OF FREE-RADICALS AT THE SURFACE OF FIBERS

The ability of respirable amosite and crocidolite asbestos, refractory ceramic fibres (RCFs) and man made vitreous fibres (MMVFs) to cause f ree radical injury to plasmid, phi X174 RFI DNA was assessed. The amos ite and crocidolite asbestos caused substantial damage to the DNA and, in the main, the free radicals responsible for the asbestos-mediated DNA damage were hydroxyl radicals as bi determined by inhibition with mannitol. Asbestos fibre-mediated damage to the DNA was completely ame liorated by the chelation of fibre-associated iron by pre-treatment of fibres with desferrioxamine-B, confirming the importance of iron in t he production of free radicals. MMVFs and RCFs produced modest free ra dical damage to the DNA, which was prevented by mannitol but not by ir on chelation.