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the claim

Propylene glycol and glycerin form formaldehyde and acetaldehyde when vaporized

the verdict
SUPPORTED
the evidence backs this
Recorded sources
6 sources for · 0 against

Counts group repeated records of the same source within each side. They do not measure evidence strength or source independence.

Is it true that Propylene glycol and glycerin form formaldehyde and acetaldehyde when vaporized?

Yes. Multiple studies demonstrate that propylene glycol and vegetable glycerin thermally degrade during vaporization to form toxic aldehydes, specifically including formaldehyde and acetaldehyde.

Verdict: SUPPORTED · 6 sources for, 0 against · Last checked

The analysis

Every retrieved paper examining the thermal degradation or emissions of propylene glycol and glycerin (glycerol) in electronic delivery systems reports the formation of formaldehyde, acetaldehyde, and other toxic carbonyls. The evidence is unanimous and robust, supporting the claim entirely.

Evidence for · 6
Toxicity of humectants propylene glycol and vegetable glycerin in electronic nicotine delivery systems.
2025
Identifies formaldehyde and acetaldehyde among the thermal degradation byproducts generated by PG and VG in e-cigarette aerosols.
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Y, S., K, L., F, E., F, C. B., D, L., S, M., MD, M., & I, R. (2025). Toxicity of humectants propylene glycol and vegetable glycerin in electronic nicotine delivery systems.. doi.org. https://doi.org/10.1016/j.toxlet.2025.111739

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More for · 5
Electronic Cigarettes: Their Constituents and Potential Links to Asthma.
2017
Notes that thermal decomposition of propylene glycol and vegetable glycerin produces reactive carbonyls including formaldehyde and acetaldehyde.
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Clapp, P. W. & Jaspers, I. (2017). Electronic Cigarettes: Their Constituents and Potential Links to Asthma.. doi.org. https://doi.org/10.1007/s11882-017-0747-5

Determining the impact of flavored e-liquids on aldehyde production during Vaping.
2020
States that 1,2-propylene glycol and glycerin, as principal components of e-liquids, thermally degrade to form acetaldehyde and formaldehyde when heated.
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Gillman, I. G., Pennington, A. S. C., Humphries, K. E., & Oldham, M. J. (2020). Determining the impact of flavored e-liquids on aldehyde production during Vaping.. doi.org. https://doi.org/10.1016/j.yrtph.2020.104588

Low-temperature (< 200 °C) degradation of electronic nicotine delivery system liquids generates toxic aldehydes.
2021
Demonstrates through nuclear magnetic resonance that the degradation of e-system liquids generates formaldehyde and acetaldehyde.
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Jaegers, N. R., Hu, W., Weber, T. J., & Hu, J. Z. (2021). Low-temperature (< 200 °C) degradation of electronic nicotine delivery system liquids generates toxic aldehydes.. doi.org. https://doi.org/10.1038/s41598-021-87044-x

Carbonyl Composition and Electrophilicity in Vaping Emissions of Flavored and Unflavored E-Liquids.
2021
Confirms that PG and VG emitted significant levels of formaldehyde and acetaldehyde during vaping emissions.
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Chen, J. Y., Canchola, A., & Lin, Y. (2021). Carbonyl Composition and Electrophilicity in Vaping Emissions of Flavored and Unflavored E-Liquids.. doi.org. https://doi.org/10.3390/toxics9120345

Emissions from Electronic Cigarettes: Key Parameters Affecting the Release of Harmful Chemicals.
2016
Reports that toxic aldehydes including formaldehyde and acetaldehyde originate from the heating of base e-liquid solvents like PG and glycerin.
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Sleiman, M., Logue, J. M., Montesinos, V. N., Russell, M. L., Litter, M. I., Gundel, L. A., & Destaillats, H. (2016). Emissions from Electronic Cigarettes: Key Parameters Affecting the Release of Harmful Chemicals.. doi.org. https://doi.org/10.1021/acs.est.6b01741

What does the evidence say?

Every retrieved paper examining the thermal degradation or emissions of propylene glycol and glycerin (glycerol) in electronic delivery systems reports the formation of formaldehyde, acetaldehyde, and other toxic carbonyls. The evidence is unanimous and robust, supporting the claim entirely.

Receipt History
first checked04 Aug 2026
judged → SUPPORTED · 7904 Aug 2026
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