The effect of varying battery voltage output on the emission rate of carbonyls released from e-cigarette smoke

The effect of vaping voltage (range: 3.6 to 7.0 V) on the emission of carbonyl compounds (CC) from electronic cigarettes (ECs) was investigated in this study. Changes in the CC levels were compared between prior to (e-liquid samples) and after vaping (EC-aerosol samples) using a total of six different e-liquid samples. Three of them were lab-made binary e-liquid solutions (composed only of propylene glycol (PG) and vegetable glycerin (VG) at the following 3 mixing ratios: 7:3, 5:5, and 10:0), while the remaining three were retail e-liquid products. The CCs in aerosol samples were captured from 10 EC puffs on 2,4-dinitrophenylhydrazine (DNPH) cartridges (2 s puff duration with a 10 s interpuff interval). All six e-liquids analyzed prior to EC use contained formaldehyde (FA) and acetaldehyde (AA) in the range of 0.12-50.0 and 0.53-14.9 mu g mL(-1), respectively. As the vaping voltage increased from 3.6 to 7.0 V, their emission factors increased from 1.12 to 1.64 and from 1.30 to 2.02 (mu g puff(-1)), respectively. Such patterns were also observed for other CCs. The 40-year cancer risk (CR) of FA and CA for a typical user (120 puffs day(-1)) was estimated to be 7.0 x 10(-4)-1.1 x 10(-3) and 3.2 x 10(-3)-1.4 x 10(-4), respectively; these CR values increased by 1.2 and 1.7-2.0 times, respectively with an increase in vaping voltage (3.6-7.0 V). The CR due to FA exposure from the three tested retail e-liquids was estimated to be 2.6-56 times higher than that of traditional tobacco cigarettes. Therefore, the use of ECs may expose users to high levels of certain CCs (like FA and AA), which may increase the risk for cancer in humans.