In India, over 3 million workers employed in the bidi industry receive massive, chronic exposure to unburnt tobacco, mainly by the cutaneous and nasopharyngeal routes. While the hazards of habitual tobacco usage are well established, very little information is available about the effects of occupational tobacco exposure. In the present study, tobacco processing plant workers (TPPW) and bidi rollers (BR) with or without tobacco habits were monitored for occupation-related exposure to tobacco and resultant genotoxicity. Salivary cotinine levels were determined as an index of tobacco exposure and micronucleated buccal epithelial cell (MNC) frequency was recorded as a genotoxic endpoint. Occupational tobacco exposure led to the detection of cotinine in the saliva of 19% of BR and 100% of TPPW with no tobacco habit (NH). The greater degree of exposure in TPPW was evident from the significantly higher mean salivary cotinine level in TPPW-NH as compared to BR-NH (2.86 +/- 0.48 vs. 0.84 +/- 0.26 micrograms/ml; p < 0.01). The effect of occupational exposure was also evident in TPPW and BR with the masheri habit. A moderate but statistically significant increase in MNC frequency was observed in habit-free as well as masheri-habituated TPPW and BR as compared with the respective controls. The findings provide preliminary evidence for the clastogenic effects of occupational tobacco exposure.