Smokers who use e-cigs 'are risking harm to their lungs': Tests on 50 types of device find most contain chemical responsible for incurable condition known as 'popcorn lung'

Tests on more than 50 types of electronic cigarettes found most contain a chemical blamed for an incurable condition called 'popcorn lung' (file image)

They are seen as a safe alternative to tobacco – but e-cigarettes could still harm your lungs.

Tests on more than 50 types of electronic cigarettes found most contain a chemical blamed for an incurable condition called 'popcorn lung'.

It scars the lungs, causing shortness of breath and coughing – and can even require a lung transplant.

The e-cigarettes found to contain the chemical included flavours likely to be popular with children, such as 'cupcake', 'fruit squirts' and 'cotton candy'.

The study was carried out in the US but researchers believe the brands on sale in the UK are also likely to be suspect.

The discovery will alarm those who have embraced 'vaping' in the belief that it is harmless. An estimated 2.6million people in the UK use e-cigarettes, which provide a nicotine hit without the cancer-causing chemicals found in tobacco.

Yesterday it emerged that e-cigs will soon be available on the NHS – supplied by British American Tobacco.

The e-Voke has been cleared for medicinal use and could be prescribed next year to smokers trying to quit alongside patches and gums. A review recently declared them 95 per cent safer than the real thing.

Researchers from the Harvard TH Chan School of Public Health tested 51 types of flavoured e-cigarettes sold by leading brands for the chemical diacetyl.

The e-cigarettes found to contain the chemical included flavours likely to be popular with children, such as 'cupcake', 'fruit squirts' and 'cotton candy' (stock image)

It is used to give popcorn its buttery taste and found in many other artificial flavourings.

But, when inhaled, it is thought to scar tiny air sacs within the lungs, causing coughing and shortness of breath. In severe cases, only a lung transplant will help.

The condition came to light in popcorn factories, leading it to be nicknamed 'popcorn lung'.

Researchers also looked for acetoin and 2,3-pentanedione, two other flavouring compounds that can trigger respirator problems. At least one of the three chemicals was detected in 47 of the 51 flavours tested, journal Environmental Health Perspectives reports.

Lead author Joseph Allen said: 'Recognition of the hazards associated with inhaling flavouring chemicals started with 'popcorn lung' over a decade ago.

'However, diacetyl and other related flavouring chemicals are used in many other flavours beyond butter-flavoured popcorn, including fruit flavours, alcohol flavours, and, we learned in our study, candy-flavoured e-cigarettes.

'Some 92 per cent of the flavoured e-cigarettes we tested had one of three flavouring chemicals we analysed for. These products are all available for purchase online.

'Based on the widespread use of flavourings in the industry and the high prevalence detected in our study, it's my opinion that we are likely to detect these chemicals in flavourings in many flavoured e-cigarette products in the UK and every other market in the world where these are sold.'

Study co-author David Christiani added: 'Since most of the health concerns about e-cigarettes have focused on nicotine, there is still much we do not know about e-cigarettes.

'In addition to containing varying levels of the addictive substance nicotine, they also contain other cancer-causing chemicals, such as formaldehyde, and as our study shows, flavouring chemicals that can cause lung damage.'

Public Health England had claimed at least 76,000 lives a year could be saved if smokers went electronic. But it emerged that assertion relied on a 2014 study partially conducted by scientists linked to the e-cigarette industry.

Writing in the British Medical Journal, experts said many of the conclusions were premature and based on weak evidence. Other research found the vapour from e-cigarettes makes the hard-to-treat MRSA superbug more deadly.

There is also concern e-cigarettes glamorise smoking to the young. Chief medical officer Professor Dame Sally Davies has warned they may make smoking seem normal again.