Passive smoking and sister-chromatid exchanges in lymphocytes

The object of this study was to determine whether exposure to environmental tobacco smoke is associated with DNA damage reflected by the frequency of sister-chromatid exchange (SCE) in lymphocytes. Within a cross-sectional design, 106 male non-smoking adults, employees of two administrative companies, were divided on the basis of self-reported exposure into high and low passive smoking groups. The high exposed subjects (passive smokers, n = 50) lived with smokers, worked with smokers and were exposed to tobacco smoke for an average of 70 h/week. The low exposed non-smokers (n = 56) were exposed for an average of 5 h/week. Plasma cotinine levels for the passive smokers ranged between 0.4 and 9.0 ng/ml (median 1.4 ng/ml), and for the low exposed group between 0.0 and 1.9 ng/ml (median 0.4 ng/ml) (p less than 0.0001; Mann-Whitney test). No difference was observed between the two groups in the frequency of SCEs in lymphocytes: 4.66 +/- 0.05 for passive smokers and 4.68 +/- 0.04 for low exposed non-smokers (mean +/- SEM) (p = 0.80; t-test). Reclassification of subjects on the basis of plasma cotinine levels did not change the results substantially. These results are in accordance with observations that the increase in cancer risk due to passive smoking is small in comparison with the increase due to active smoking. The SCE test may be too insensitive to be useful for the evaluation of possible cytogenetic effects related to passive smoking.