Background:
The Japanese government is trying to establish effective countermeasures for avoidance of secondhand smoke in indoor environments for tobacco-free Tokyo Olympic and Paralympic games 2020, as requested by the International Olympic Committee (IOC) and the World Health Organization (WHO). On the other hand, the tobacco industries have launched heat-not-burn (HNB) tobacco products which it claims is designed to produce less harmful components in Japan recently. Smokers strongly demand for products claiming or implying reduced health risks. There is little scientific data, however, of the hazards and toxicity of HNB tobacco.

Methods:
In this study, we evaluated several harmful compounds (nicotine, tar, carbon monoxide (CO) and tobacco-specific nitrosamines (TSNAs)) in the mainstream aerosol and fillers of iQOS produced by Philip Morris International (PMI), and compared their concentrations with those from conventional combustion cigarettes.
Mainstream aerosol was collected under the conditions of 55 ml puff volume, 2 s puff duration, 30 s puff interval, and 100% blocking of the filter ventilation holes according to the Health Canada, Official Method T-115.

Results:
The concentrations of nicotine in tobacco fillers and the mainstream aerosol of iQOS were almost the same as those of conventional combustion cigarettes, while the concentration of TSNAs was one fifth and CO was one hundredth of those of conventional combustion cigarettes.

Conclusions:
"Tobacco companies continue reassuring health concerned smokers by offering with their new products the illusion of safety (WNTD 2006)." The market share of HNB tobaccos have been rapidly increased in Japan. One reason why HNB may be gaining market share is that nicotine-containing ENDS are prohibited for sale in Japan. PMI applied for US-FDA approval of the heat-not-burn tobacco product "iQOS" as a modified risk tobacco product in 2016. Although it is low concentration in this study, toxic compounds are definitely included in the mainstream aerosol of iQOS.