People who use e-cigarettes, smokeless tobacco products exposed to high levels of cancer-causing chemical pulegone
A cancer-causing chemical - which was banned by the US Food and Drug Administration (FDA) as a food additive in 2018, is present at dangerously high levels in electronic cigarette liquids and smokeless tobacco products.
The chemical - called pulegone - is a carcinogen (a substance capable of causing cancer) and has been found to cause hepatic carcinomas (a type of liver cancer), and some other type of cancer in animal studies. It is found in menthol and mint-flavored e-cigarettes and smokeless tobacco products.
The FDA banned pulegone as a food additive in response to petitions from consumer groups because of its carcinogenic properties. However, it does not have a similar policy to regulate the presence in e-cigarettes and smokeless tobacco, which are promoted as safer alternatives to regular cigarettes.
The findings, published in JAMA Internal Medicine, show that the flavoring ingredient exceeds safety levels in e-cigarettes and smokeless tobacco. "Our analysis suggests that users of mint- and menthol-flavored e-cigarettes and smokeless tobacco are exposed to pulegone levels higher than (what) the FDA considers acceptable for intake in food, and higher than in smokers of combustible menthol cigarettes," says Dr. Sven-Eric Jordt, lead author of the study and Professor of the Department of Anesthesiology at Duke University.
Two earlier studies by the US Centers for Disease Control and Prevention (CDC) had detected substantial amounts of pulegone in mint- and menthol-flavored e-cigarette liquids and smokeless tobacco products marketed in the US.
Accordingly, the researchers decided to analyze whether several top brands of regular menthol cigarettes, three e-cigarette brands, and one smokeless tobacco brand contain enough pulegone to be a cause for concern. They compared the CDC-reported amounts of pulegone with the exposure risk data of the FDA. These are the levels at which exposure-related tumors were reported in animal studies.
"Margin of exposure is the measure used by the FDA and other regulatory agencies for cancer risk assessment of food additives. Cancer risk is inversely proportional to the margin of exposure, with values of 10,000 or below requiring mitigation strategies. We compared the risk associated with pulegone content in top marketed brands of combustible menthol cigarettes to mint- and menthol-flavored e-cigarettes and smokeless tobacco,” says the research team.
They add, “Based on daily use, we considered a light user to consume 5 mL of e-liquid, half a pack of cigarettes, or 10 g of smokeless tobacco; a moderate user to consume 10 mL of e-liquid, 1 pack of cigarettes, or 20 g of smokeless tobacco; and a heavy user to consume 20 mL of e-liquid, 2 packs of cigarettes, or 30 g of smokeless tobacco.”
The analysis shows that the levels in the e-cigarettes and smokeless tobacco “exceeded the thresholds of concern.” However, regular menthol cigarettes contained levels below the limits, the findings state.
The researchers found that daily pulegone exposure from e-cigarettes compared with menthol cigarette use was higher across all user groups - and ranged from 44-1,608 times higher. Compared with menthol cigarettes, estimated pulegone intake from smokeless tobacco was 168 to 1,319 times higher in light users and 126 to 990 times higher in heavy users.
According to the research team, the dangers of pulegone has been long known by the tobacco industry, which has been trying to minimize its levels in menthol cigarette flavorings. This could explain why the levels are much lower in menthol cigarettes than in electronic cigarettes.
"Although pulegone is toxic in humans, it is unknown if users of combustible tobacco products, smokeless tobacco, or e-cigarettes absorb and metabolize the quantities associated with the production of a carcinogenic effect," says the researchers, adding that further research is needed in this area.
The findings, researchers say, indicate that the FDA must implement measures to mitigate pulegone-related health risks before suggesting mint- and menthol-flavored e-cigarettes and smokeless tobacco products as alternatives for people who smoke regular cigarettes.
"Our findings appear to establish health risks associated with pulegone intake and concerns that the FDA should address before suggesting mint- and menthol-flavored e-cigarettes and smokeless tobacco products as alternatives for people who use combustible tobacco products," says the team.