A recent study raised concerns about the possible toxicity of flavouring additives in e-liquids, identifying several chemical compounds which are considered respiratory irritants. The researchers pointed out that the analysed liquids did not comply with the current EU regulations on e-cigarettes (Tobacco Products Directive).

However, in response to the study renowned tobacco researcher Dr. Konstantinos Farsalinos pointed out that although the flavouring chemicals were identified and quantified, the study did not calculate the potential toxicity of the chemicals in relation to their concentrations.

One chemical (methyl cyclopentenolone) was found at a maximum concentration 150.7% higher than that needed to be classified as toxic,”

To this effect, Farsalinos replicated the study examining the toxicity classification for the different chemicals at the maximum concentrations, as reported by the initial study. The aim was determining whether there is a legal requirement to include warning labels to the products, according to flavouring levels as dictated by the TPD regulations.

Farsalinos and his team compared the concentration of each flavouring compound with the minimum concentration needed to classify it as toxic. Additionally, the researchers analysed the toxicity classification for a theoretical e-cigarette liquid containing all flavouring chemicals at the maximum concentrations reported.

“There was at least one toxicity classification for all the flavouring chemicals, with the most prevalent classifications related to skin, oral, eye and respiratory toxicities. One chemical (methyl cyclopentenolone) was found at a maximum concentration 150.7% higher than that needed to be classified as toxic,” reported the researchers.

“For the rest, the maximum reported concentrations were 71.6 to > 99.9% lower than toxicity concentrations. A liquid containing all flavouring compounds at the maximum concentrations would be classified as toxic for one category only due to the presence of methyl cyclopentenolone; a liquid without methyl cyclopentenolone would have 66.7 to > 99.9% lower concentrations of flavourings than those needed to be classified as toxic.”

Flavouring compounds found at levels far lower than levels considered toxic

Farsalinos and his team concluded that the vast majority of flavouring compounds in e-cigarette liquids as reported in the initial study, were present at levels far lower than is required to be classified as toxic. They added that since not all liquids are created equal, “regulatory monitoring of liquid composition is warranted”.

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