DNA strand breaks caused by exposure to ozone and nitrogen dioxide

The present study demonstrates that exposure to ozone (O-3) and nitrogen di oxide (NOB) can cause DNA single-strand breaks in alveolar macrophages. Thr ee-month-old male Sprague-Dawley rats, specific pathogen free, were exposed to either 1.2 ppm NO2 or 0.3 ppm O-3 alone or a combination of these two o xidants continuously for 3 days, The control group was exposed to filtered room air. The oxidant effects were substantiated by determining total and d ifferential cell counts, lactate dehydrogenase activity, and total soluble protein in bronchoalveolar lavage. DNA damage was measured as single-strand breaks by alkaline elution assay, The results showed that, relative to con trol, NO2 exposure did not cause any significant change in the parameters s tudied. Exposure to O-3 and combined exposure to NO2 and O-3 caused signifi cant changes in all parameters studied except cell viability. The rates of elution (K-c) of single-strand DNA from polycarbonate filter for O-3 exposu re and combined exposure were 73 and 79% faster than that of the control, r espectively. The amounts of DNA single-strand breaks caused by O-3 and comb ined exposure were significantly greater than the amounts detected for the NO2-exposed and control groups. (C) 1999 Academic Press.