Introduction: Exposure to tobacco smoke is an extremely important risk factor determining the development of respiratory diseases, cardiovascular diseases and cancer. Passive exposure is common and often not realized by the exposed subjects. Markers of tobacco smoke exposure are nicotine metabolites, i.e. cotinine and trans-3'-hydroxycotinine.

Objectives: The objective of the study was to assess the level of passive exposure to tobacco smoke among students and the exposure impact on the blood hemoglobin level, peak expiratory flow (PEF), lipid peroxidation level and antioxidant enzyme activity.

Patients and methods: A total of 104 subjects were enrolled in the study. The subjects were categorized in 3 subgroups depending on nicotine metabolite levels in blood (subgroup I with metabolite level > 100 ng/ml (high exposure); subgroup II with the metabolite level of 10-100 ng/ml; subgroup III with metabolite level <10 ng/ml). The blood hemoglobin level, PEF, levels of lipid peroxidation metabolites--malondialdehyde and 4-hydroxynonenal (MDA + 4-HNE) and catalase (CAT) activity were determined in all the subjects.

Results: The study showed statistically significant differences in levels of lipid peroxidation metabolites and CAT activity. Levels of MDA + 4-HNE were higher in subgroup I than in subgroup II or III (I: 3.84 +/- 1.64 mmol/l; II: 2.25 +/- 0.94 mmol/l; III: 1.90 +/- 0.82 mmol/l; pI-II < 0.01; pI-III <0.001). CAT activity was statistically significantly lower in subgroup I than in subgroup III (I: 0.38 +/- 0.01 x 10(6) IU/g hemoglobin [Hb]; II: 0.38 +/- 0.03 x 10(6) IU/g Hb; III: 0.41 +/- 0.04 x 10(6) IU/g Hb; pI-III <0.05).

Conclusions: Passive exposure to tobacco smoke in the study population of students is common. The observed effects of passive exposure to tobacco smoke are similar to those of active smoking. It is postulated to undertake actions aiming at limiting passive exposure to tobacco smoke.