Flavoured e-cigarettes may damage lung tissue, leading to respiratory disease or even cancer, research suggests.
Scientists from the University of Rochester in New York identified 40 chemicals in seven flavours of JUUL pods.
When exposed to human lung tissue in the laboratory, the chemicals triggered inflammation and “degraded the integrity” of the cells.
They also damaged the cells’ DNA, “a potential precursor to cancer”.
This comes after the US was hit by a string of vaping-related deaths earlier this year.
As of November 12, 38 fatalities and 2,000 lung injury cases had been recorded, the Independent reported.
Vitamin E acetate, an oily chemical added to certain tetrahydrocannabinol (THC) vaping liquids, is thought to be to blame after the substance was found in every deceased’s lung fluid sample.
THC - the psychoactive compound of cannabis that makes users’ “high” - and vitamin E acetate are both banned in the UK, where no vaping deaths have been confirmed.
President Donald Trump announced he was considering banning all flavoured e-cigarettes, with several states already in the process of doing so.
JUUL, which makes up 70% of vape sales in the US, announced it has halted the output of most of its flavoured pods.
It continues to sell menthol, however, which was found to be equally as harmful as those that have been temporarily discontinued.
The Rochester scientists also worry other manufacturers and shops may still be producing thousands of different harmful flavours.
“While names like mango, cucumber, and mint give the impression the flavours in e-juices are benign, the reality is these sensations are derived from chemicals,” lead author Professor Irfan Rahman said.
“These findings indicate exposure to these chemicals triggers damage and dysfunction in the lungs that are a precursor to long-term health consequences.
“Other than propylene glycol and vegetable glycerin, which form the base of vaping liquids, and nicotine, most manufacturers do not disclose the chemical compounds used to create the flavours in vaping products.”
The scientists exposed human lung tissue to aerosolised vapour from the pods, they described in the journal Scientific Reports.
The lung tissue included bronchial epithelial cells, which is involved in gas exchange, and monocytes, which fight infections.
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“The chemicals provoked inflammation and degraded the integrity of the epithelial cells, a condition that could eventually lead to acute lung injury and respiratory illness,” Professor Rahman said.
“Exposure also damaged DNA in the cells, a potential precursor to cancer.”
The scientists worry too little is known about the long-term impact of e-cigarettes.
"Vaping technology has only existed for a short period of time and its use, particularly among younger people, has only recently exploded,” Professor Rahman said.
“This study gives further evidence that vaping, while less harmful than combustible tobacco in the short run, is placing chronic users on the path to significant health problems later in life.”