Discussing The Presence of Carbony in Vapes- The Latest Data

Carbonyl chemicals in cigarette smoke are a major cause of smoking-related diseases and death. Because of this, understanding carbonyl emissions is important when studying tobacco harm reduction products like vapes, to compare their risks with traditional cigarettes.

Diane Caruana

March 18, 2025

It is known that propylene glycol (PG), vegetable glycerin (VG), and flavouring chemicals can break down under heat during vaping, producing harmful chemicals called carbonyls. However, less is understood about how flavour chemicals themselves produce carbonyls and how the ingredients in e-liquids interact to create these compounds. Additionally, the research on their effect on human health and the actual amounts that are inhaled, is vast but limited, since it cannot be conducted in a real setting – ie in one’s lungs.

The 2021 study, “Carbonyl Composition and Electrophilicity in Vaping Emissions of Flavoured and Unflavoured E-Liquids“, analyzed the carbonyl chemicals released when vaping PG-VG (the main e-liquid solvents) and four flavoured e-liquids containing trans-2-hexenol, benzyl alcohol, l-(-)-menthol, or linalool. Using advanced testing methods (gas and liquid chromatography-mass spectrometry), researchers identified and measured 14 different carbonyl compounds.

PG-VG alone produced the highest levels of formaldehyde, acetaldehyde, and acrolein—three harmful chemicals, while flavoured e-liquids, generated a wider variety of carbonyls. Some of these directly formed through the chemical breakdown of flavouring ingredients. For example, trans-2-hexenol became trans-2-hexenal, and benzyl alcohol transformed into benzaldehyde.

The study also found evidence that some carbonyls (such as formaldehyde and trans-2-hexenal) can react with biological molecules in the body, raising concerns about potential health risks. By analyzing the chemical reactivity of these carbonyls, researchers further explained how different compounds produced during vaping could interact with biological systems. Overall, the study highlighted the presence of harmful carbonyl compounds in vaping emissions and emphasized the potential health risks associated with these chemicals.

Vapes emit significantly lower carbonyls than cigarettes

Meanwhile, the most recent study on the topic took a different angle. The review critically analyzed 14 studies—11 independent and three industry-funded—that examine carbonyl emissions from Electronic Cigarettes (ECs). The focus was on evaluating the analytical methods and experimental procedures used in these studies to determine their reliability.

The review set forth four key criteria for determining experimental quality:

Sufficient information on devices and procedures for reproducibility.
Use of puffing protocols that closely mimic consumer usage.
Application of appropriate analytical methods.
Use of blank samples to avoid false positives.

Seven studies were deemed reliable, five partially reliable, and two unreliable. And in line with arguments by tobacco harm reduction experts, all reproducible studies reported carbonyl yields far below those found in tobacco smoke, even in the partially reliable studies. This supports the potential of ECs as harm reduction tools when properly tested and used.

Carbonyl levels in vapour tend to be in levels insignificant to human health

In fact, an earlier review led by renowned researcher in the field – Dr. Konstantinos Farsalinos reiterated that carbonyl emissions from vapes were much lower than those from tobacco cigarettes. This study reviewed 32 research papers from PubMed that analyzed carbonyl emissions from e-cigarettes, and set to compare their risks with traditional cigarettes.

Newer vape models, like those with bottom coils and cotton wicks, produced very low carbonyl levels that may not pose significant health risks.

The review found many differences in how the studies were conducted, including variations in how e-cigarette puffs were taken, how aerosol was collected, and how results were measured. These differences make it hard to compare findings, and in some cases, the accuracy of the results was unclear.

A major issue is that most studies did not account for “dry puffs”—a condition where the device overheats and produces unusually high levels of harmful chemicals. This was especially true for studies using adjustable-power devices. Dry puffs do not reflect how people actually use e-cigarettes, meaning the reported carbonyl levels in these studies may not be relevant to real-life use. Some studies confirmed the presence of dry puffs by repeating their tests.

The review did find that few studies reported extremely high carbonyl emissions, which could have serious health impacts, however when e-cigarettes were tested under normal conditions, their carbonyl emissions were relatively lower than those from cigarettes. Moreover, newer vape models, like those with bottom coils and cotton wicks, produced very low carbonyl levels that may not pose significant health risks.

The potential of vapes as harm reduction tools indicated once again

While research confirms that vaping produces harmful carbonyl compounds, studies consistently show that vapes emit significantly fewer carbonyls than traditional cigarettes when tested under realistic conditions. Reliable studies demonstrate that proper testing methods are crucial, as factors like “dry puffs” can distort findings. Although some flavoured e-liquids generate a wider range of carbonyls, the overall levels remain lower than those in cigarette smoke. Future research should prioritize standardized testing protocols to accurately assess long-term health impacts and better understand the risks associated with vaping under normal use conditions.