There may be no safe 'smoking' alternative to cigarettes, scientists have suggested.
Popular heated tobacco devices may cause the same damage to lung cells as traditional cigarettes, they said.
Meanwhile, e-cigarettes – or vaping, as it's commonly known – are also toxic to the cells which protect the lungs, so may not be a safe alternative either.
Both electronic devices, used by thousands of people to quit smoking, are now thought to cause the airway damage seen in people with the lung diseases emphysema, bronchitis and cancer.
Australian researchers found they harm the lung cells which protect the airways, in a similar way to cigarette smoke.
But campaigners are sceptical and say vaping and heated tobacco are still safer than smoking cigarettes.
The study looked at the IQOS, a ‘next-generation’ heated tobacco device used by 6.6million people and sold globally.
Priced at more than £50 for a starter kit from Amazon, the trendy product heats rather than burns tobacco to produce a similar flavour to cigarettes but lower levels of chemicals.
However, in the study, it was found to damage human lung cells by changing their structure and triggering an inflammatory response.
Dr Sukhwinder Sohal led the study from the University of Tasmania, looking at cigarettes, e-cigarettes and the IQOS, which is made by tobacco giant Philip Morris International.
He said: "Our results suggest that all three are toxic to the cells of our lungs and that these new heated tobacco devices are as harmful as smoking traditional cigarettes."
"Damage to these two types of lung cells can destroy lung tissue leading to fatal diseases such as chronic obstructive pulmonary disease, lung cancer and pneumonia, and can increase the risk of developing asthma, including in unborn children.
"So we should not assume that these devices are a safer option."
Cigarettes, electronic cigarettes and heated tobacco devices all contain nicotine - the addictive substance which gets people hooked.