ArticleTobacco control2026
Water addition to e-liquids to reduce flavour aldehyde acetal formation: chemistry and user sensory experience and appeal.
Article in Tobacco control, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT05257109 (Water Content In E-Liquids), which is not on this map. Not yet cited in PubMed.
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Water Content In E-Liquids
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Abstract
backgroundAldehydes are common e-liquid flavourants that undergo chemical reactions with the e-liquid solvents propylene glycol (PG) and glycerol (G) to form acetals. Some flavour aldehyde PG acetals are respiratory irritants and may have negative user effects. Water-a byproduct of acetal formation-can shift the chemical equilibrium back towards the flavour aldehydes. This study combined chemical and human experiments to assess effects of water addition on acetal formation in laboratory-made e-liquids, commercial products and user experience.
methodsAcetal content was monitored in laboratory-made e-liquids containing PG and one flavour aldehyde (benzaldehyde, cinnamaldehyde, ethylvanillin and vanillin) and commercial e-liquids based on PG/G with corresponding flavours (Cherry, Cinnamon, Vanilla and Grape as non-aldehyde-containing control) containing 0%-20% water over 28 days. E-cigarette users (n=30, 35.3 years (10.4), 51.7% female) assessed sensory and appeal outcomes of the diluted commercial e-liquids (no-added-water, 5%, 10% and 20%). Mixed-effects models assessed main effects of water, flavour and interactions.
resultsWater addition reduced PG-acetal buildup in laboratory-made e-liquids 1.3-38-fold depending on water content (more water was more effective) and flavour aldehyde (vanillin>ethylvanillin>cinnamaldehyde>benzaldehyde). Water addition to commercial e-liquids reversed combined PG/G-acetal content up to 26-fold. Among e-cigarette users, 20% water content (but not 5% and 10%) significantly lowered liking and reward (vs no-added-water). Water addition did not impact sensory outcomes.
conclusionsWater appears to have a limited effect on appeal at ≤10%, while reducing flavour aldehyde acetal formation. Therefore, water addition to e-liquids may be an elegant regulatory approach to reduce exposure to potentially harmful flavour aldehyde acetals in e-cigarettes. TRIAL REGISTRATION NUMBER: NCT05257109.
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