A VAPING-related lung disease which has killed 16 people in the US and one Brit is caused by toxic fumes, experts believe.
Researchers reviewed lung biopsies from 17 e-cigarette users who were suspected to have a vaping-associated lung injury.
The Mayo Clinic study, published in The New England Journal of Medicine today, is the first of its kind.
It comes after a surge of people being struck down with a mysterious and life-threatening lung disease in the US.
The number of people who have succumbed to the disease has now reached 16, after health bosses in Virginia and New Jersey reported fatalities last night.
Meanwhile, the first British victim reported to have died from the vaping-related lung illness was named as Terry Miller, 57, from Gateshead, Tyne and Wear.
In this latest research, experts say they found that lung injuries were most likely caused by direct toxicity or tissue damage from noxious chemical fumes.
There was no evidence of tissue injury caused by accumulation of lipids – fatty substances such as mineral oils – which has been suspected as a possible cause of the mysterious disease, they said.
It seems to be some kind of direct chemical injury, similar to what one might see with exposures to toxic chemical fumes, poisonous gases and toxic agents
Brandon Larsen, a surgical pathologist at Mayo Clinic Arizona, and a national expert on lung pathology, said: "While we can't discount the potential role of lipids, we have not seen anything to suggest this is a problem caused by lipid accumulation in the lungs.
"Instead, it seems to be some kind of direct chemical injury, similar to what one might see with exposures to toxic chemical fumes, poisonous gases and toxic agents."
Of the 17 biopsies that were examined, two were from Mayo Clinic patients while the others were from hospitals around the country that were sent to the medical center for further investigation.
All of the patients had vaped, and 71 per cent had vaped with marijuana or cannabis oils.
They all showed acute lung injury, including pneumonitis, and two of the patients died.
Dr Larsen, senior author of the study, said: "We were not surprised by what we found, regarding toxicity.
"We have seen a handful of cases, scattered individual cases, over the past two years where we have observed the same thing, and now we are seeing a sudden spike in cases.
"Our study offers the first detailed review of the abnormalities that may be seen in lung biopsies to help clinicians and pathologists make a diagnosis in an appropriate clinical context."
Vaping-associated lung injury can be difficult to diagnose unless clinicians and pathologists are armed with information beforehand, Dr Larsen says.
He added: "This is a public health crisis, and a lot of people are working frantically around the clock to find out what the culprit or culprits could be – and what chemicals may be responsible.
"Based on what we have seen in our study, we suspect that most cases involve chemical contaminants, toxic byproducts or other noxious agents within vape liquids."
We suspect that most cases involve chemical contaminants, toxic byproducts or other noxious agents within vape liquids.
In the meantime, the public should heed what leading medical organizations and public health agencies are saying about the dangers of vaping.
"Everyone should recognize that vaping is not without potential risks, including life-threatening risks, and I think our research supports that," he says.
"It would seem prudent based on our observations to explore ways to better regulate the industry and better educate the public, especially our youth, about the risks associated with vaping."
Arises in cases
The US Centers for Disease Control has stated that there are now 805 confirmed cases of people being struck down with the mysterious and life-threatening lung disease in the US.
Earlier this week, it was revealed that a man from Nebraska died in May before the epidemic in the US was officially reported.
Last week, three victims were reported in Mississippi, Georgia and Florida.
Prior to that, there were two deaths in California, two in Kansas, two in Oregon, and one each in Illinois, Indiana, Minnesota and Missouri, according to the CDC.
The growing death toll has prompted officials to launch a criminal investigation.
How safe are e-cigarettes in the UK?
In the UK, e-cigarettes are tightly regulated for safety and quality.
They are not completely risk free, but they carry a small fraction of the risk of cigarettes.
E-cigarettes do not produce tar or carbon monoxide, two of the most harmful elements in tobacco smoke.
The liquid and vapor contain some potentially harmful chemicals also found in cigarette smoke, but at much lower levels.
While nicotine is the addictive substance in cigarettes, it's relatively harmless.
Almost all of the harm from tuxedo comes from the thousands of other chemicals in tobacco smoke, many of which are toxic.
Nicotine replacement therapy has been widely used for many years to help people stop smoking and is a safe treatment.
There's no evidence so far that vaping causes harm to other people around you.
This is in contrast to secondhand smoke from tuxedo which is known to be very harmful to health.
However, they are still struggling to identify a single chemical product in e-cigarettes behind the outbreak.
Mitch Zeller, the director at the Food and Drug Administration, said: "The focus is on the supply chain."
The illness was first reported in April and all patients are known to have used e-cigarettes – some containing the cannabinoid THC.
Symptoms can include fatigue, coughing, breathlessness, and vomiting or diarrhea.
States have begun banning e-cigarette sales and the first case has been reported in Canada.
A report from the Medicines and Healthcare Regulatory Agency in the UK says 200 health problems are linked with e-cigarette use.
The health watchdog has recorded 74 reports of health problems suspected to have been caused by e-cigarettes since 2014.
VAPE FEARS GROW
Vaping death toll rises to 16 in US after first reported UK death
Factory worker thought to be first Brit to die from vaping-linked lung disease
Vaping death toll rises to 13 – with 805 cases of e-cigarette lung disease
Boss of e-cigarette firm Juul steps down amid US vaping lung disease outbreak
TIME TO QUIT?
Vaping death toll hits 11 – Californians told to quit over disease fears
TIME TO QUIT?
Vaping death toll rises to nine as man dies from e-cigarette lung disease
Shocking scans show how vaping can BLOCK your lungs with solidified oil as 8 die
Vaping death toll hits eight as lung disease outbreak surges to 530 cases
Of them, 49 were classified as "serious".
Experts are now calling on a national system to record every problem associated with e-cigarettes, according to the Sunday Times.
But the MHRA insisted all health problems are reviewed, adding that they are not concrete proof of the side effects of vaping.
We pay for your stories! Do you have a story for The Sun Online news team? Email us at firstname.lastname@example.org or call 0207 782 4368. You can WhatsApp us on 07810 791 502. We pay for videos too. Click here to upload yours.