E-cigarettes generate high levels of aldehydes only in 'dry puff' conditions

Background and aims: Aldehydes are emitted by electronic cigarettes due to thermal decomposition of liquid components. Although elevated levels have been reported with new-generation high-power devices, it is unclear whether they are relevant to true exposure of users (vapers) because overheating produces an unpleasant taste, called a dry puff, which vapers learn to avoid. The aim was to evaluate aldehyde emissions at different power levels associated with normal and dry puff conditions.

Design: Two customizable atomizers were prepared so that one (A1) had a double wick, resulting in high liquid supply and lower chance of overheating at high power levels, while the other (A2) was a conventional setup (single wick). Experienced vapers took 4-s puffs at 6.5 watts (W), 7.5 W, 9 W and 10 W power levels with both atomizers and were asked to report whether dry puffs were generated. The atomizers were then attached to a smoking machine and aerosol was trapped.

Setting: Clinic office and analytical chemistry laboratory in Greece.

Participants: Seven experienced vapers.

Measurements: Aldehyde levels were measured in the aerosol.

Findings: All vapers identified dry puff conditions at 9 W and 10 W with A2. A1 did not lead to dry puffs at any power level. Minimal amounts of aldehydes per 10 puffs were found at all power levels with A1 (up to 11.3 µg for formaldehyde, 4.5 µg for acetaldehyde and 1.0 µg for acrolein) and at 6.5 W and 7.5 W with A2 (up to 3.7 µg for formaldehyde, 0.8 µg for acetaldehyde and 1.3 µg for acrolein). The levels were increased by 30 to 250 times in dry puff conditions (up to 344.6 µg for formaldehyde, 206.3 µg for acetaldehyde and 210.4 µg for acrolein, P < 0.001), while acetone was detected only in dry puff conditions (up to 22.5 µg).

Conclusions: Electronic cigarettes produce high levels of aldehyde only in dry puff conditions, in which the liquid overheats, causing a strong unpleasant taste that e-cigarette users detect and avoid. Under normal vaping conditions aldehyde emissions are minimal, even in new-generation high-power e-cigarettes.