Formate Emission in the Mainstream Aerosols of Heated Tobacco Products Distributed in Japan

Heated tobacco products (HTPs) are newly developed nicotine delivery systems via the inhalation of mainstream aerosols generated during the heating of tobacco leaf materials. Previous studies have shown that the amount of chemicals generated is much lower than that generated by conventional combustible cigarettes. However, little attention has been paid to formate, a conjugated base of formic acid with potentially toxic effects on human health. This study aims to understand the actual emission levels and behaviour of formate in mainstream aerosols produced by commercially available HTP devices in Japan. Aerosols were generated from four types of devices with regular and menthol-type flavours using a vaping machine following the CRM 81 puffing protocol. Formate was tapped in 5 mM sodium carbonate solution and subsequently analysed using ion chromatography. The results showed that the total emission amount of formate ranged from 0.0027 ± 0.0031 to 0.27 ± 0.055 mg L−1, varying with heating temperature and flavour type. Moreover, the majority of formate existed in a particulate form due to the weak-basic property of the aerosol, and the formate emission level was much greater than the workplace exposure limit for the direct inhalation of mainstream aerosols. The formate in the mainstream aerosol can be considered a health concern, when using “high-temperature type” HTPs over a long period.