Flavoured e-cigarettes contain dangerous levels of cancer-causing chemicals, scientists claim.
Toxic compounds are already known to form as a result of the gadget's rapid heating process, known as pyrolysis.
But new research has discovered flavoured liquids are creating high amounts of aldehydes - exceeding health limits.
Consuming or inhaling them, even in small amounts, has been linked to increased risk of cancer and heart disease.
The findings are a cause for concern due to the 8,000 flavours available on the market - with some designed specifically to attract young adults.
Flavoured liquids are creating high amounts of aldehydes - which are known to increase the risk of cancer, heart disease and dementia, new research suggests
Flavourings used in e-cigarettes were previously found to be mostly the same as those used in foods and have therefore passed safety tests.
However, this applies to them being eaten rather than inhaled.
Researchers from the Desert Research Institute, Nevada, measured concentrations of 12 aldehydes in aerosols produced by three common e-cigarette devices.
To determine whether the additives affected chemical production during vaping, five different flavours were tested in each device. Two unflavoured e-liquids were also used.
Real-life vaping was stimulated in each device through a four-second, 40-ml puff and 30-second resting period between each puff.
They discovered liquids with higher flavour content produced higher amounts of the aerosols due to the pyrolysis process.
