Pulmonary antioxidants exert differential protective effects against urban and industrial particulate matter

This investigation focuses on the application of an in vitro assay in elucidating the role of lung lining fluid antioxidants in the protection against inhaled particles, and to compare the toxicities of different airborne particulate matter (PM), PM10, collections from South Wales, UK. PM collections from both urban and industrial sites caused 50% oxidative degradation of DNA in vitro at concentrations as low as 12.9 +/- 2.1 microg ml(-1) and 4.9 0.9 mg ml-1 respectively. The primary source of this bioreactivity was found to be the soluble fraction of both particle collections. The coarser PM(10-2.5) fraction also showed greater oxidative bioreactivity than the PM(2.5-0.1) in both cases. When repeated in the presence of a low molecular weight fraction of fresh pulmonary lavage fluid, as well as in artificial lung lining fluid (200 microM urate, glutathione and ascorbate), the DNA damage was significantly reduced in all cases (P < 0.05). The antioxidants exerted a greater effect on the industrial samples than on the urban samples, and on the PM(10-2.5) fractions than on the PM(2.5-0.1) fractions, supporting the previous findings that respirable PM and urban samples contain fewer free radical sources than inhalable PM and industrial samples.