Acetone and isoprene concentrations in exhaled breath in healthy subjects

We measured the concentrations of acetone and isoprene in the exhaled breath from students to evaluate their lifestyles for the annual medical checkup at our university. 451 students were examined for both gases simultaneously by a gas analysis device, Biogas Acetone Analyzer (BAS-2000). The average concentrations of acetone and isoprene in the breath were 0.53 +/- 0.45 ppm and 0.065 +/- 0.058 ppm, respectively, and the frequency of the abnormal high levels by judging the cut-off values of 1.5 and 0.20 ppm were 3.5% and 2.7% of them, respectively. Acetone concentration in the breath was higher in students having no breakfast in the day of the medical checkup than those having breakfast. Furthermore, acetone concentration was significantly correlated inversely with body fat percentage in students who took the medical checkup in the morning and significantly higher in students with body mass index (BMI) under 25 than obese students with BMI over 25. On the other hand, isoprene concentration was higher in male students than female students, and also higher in smokers than nonsmokers. However, isoprene level was not affected by ingestion of breakfast in the day. Acetone and isoprene concentrations were correlated positively with each other, although the relationship was not affected by having breakfast. The results suggest that the measurement of acetone and isoprene concentrations in the breath is useful for evaluating lifestyles such as lack of breakfast, smoking and obesity in students.