Increased frequency of sister chromatid exchanges in the peripheral lymphocytes of cigarette smokers.

The incidence of sister chromatid exchanges (SCEs) in the peripheral lymphocytes of 23 smokers was significantly higher than that in 27 non-smokers (6.5 +/- 0.3 compared with 4.1 +/- 0.2 per cell, mean +/- SEM). Both the duration of smoking and the number of cigarettes smoked per day appeared to influence SCE frequency. Significantly higher frequencies of SCEs were observed in those who smoked more than 10 cigarettes per day than in those who smoked less than 10 cigarettes per day. The frequency of SCEs in those who had habitually smoked for over 10 years was significantly greater than that in those who had smoked for less than 10 years.