Objectives: The purposes of this research were to investigate the hazardous effects of heat-not-burn tobacco and to clarify the health effects accompanying the transition from cigarettes to heat-not-burn tobacco.

Methods: The concentrations of carbon monoxide, ammonia, formaldehyde, acetaldehyde, and dust (hazardous substances) were measured in the smoke of heat-not-burn tobacco. Twenty-nine smokers were used as the subjects. The concentrations of hazardous substances were measured in exhalation of heat-not-burn tobacco. The concentration of cotinine in saliva was also measured after the transition. A questionnaire survey was performed before and after the transition to evaluate nicotine dependence, nicotine withdrawal symptoms, and smoking behaviors.

Results: In the mainstream smoke, all hazardous substances investigated were detected. Carbon monoxide and dust were detected in the exhalation of heat-not-burn tobacco. The concentration of cotinine in the saliva of heat-not-burn tobacco users corresponded to that of cigarette smokers. Cigarette smoking was significantly positively related to the score of Fagerström Test for Nicotine Dependence (FTND). Heat-not-burn tobacco was significantly positively related to FTND and Minnesota Nicotine Withdrawal Scale (MNWS) scores. The group in which the number of heat-not-burn tobacco sticks consumed increased after transition showed a smaller number of cigarettes consumed and a higher MNWS score before transition than the group in which it decreased after transition. These two factors were significantly related to the difference between the numbers of cigarettes and heat-not-burn tobacco sticks in multiple linear regression analysis.

Conclusions: The mainstream smoke of heat-not-burn tobacco contains harmful substances. There were the possibilities that nicotine dependence and nicotine withdrawal symptoms appear after transition and that the number of heat-not-burn tobacco sticks consumed increases.