A STUDY OF THE SYNERGISTIC INTERACTION OF ASBESTOS FIBERS WITH CIGARETTE TAR EXTRACTS FOR THE GENERATION OF HYDROXYL RADICALS IN AQUEOUS BUFFER SOLUTION

Several models attempt to explain the synergistic increase in lung can cer among workers exposed to asbestos fibers, who were somkers at the same time. It is known that reactive oxygen species (ROS) are importan t mediators in asbestos-induced diseases, especially cancer. We studie d quantitatively the formation of ROS (by spin trapping with DMPO) in aqueous buffer suspensions containing crocidolite (UICC), chrysotile ( UICC and commercial, long fibers) alone, and in combination with aqueo us cigarette tar extracts. It was observed that asbestos and cigarette tar act in a cooperative or synergistic way in the generation of hydr oxyl radical spin adducts. Grinding of asbestos fibers and addition of EDTA (iron chelator) enhanced the intensity of the ESR signal. This e nhancement progressed with time, probably due to the reaction of the e xtracted iron with the slow released hydrogen peroxide from tar extrac ts. It was observed a fivefold increase in the ESR signal (for crocido lite and aqueous tar extracts) in the formation of hydroxyl radicals v ia an iron-catalyzed Fenton reaction. These experimental results are s uggest to be strong evidence to the fact that lung cancer has been fou nd in asbestos workers exposed to high concentrations of fibers in the working environment who were smokers, and only rarely in nonsmokers.