One study found a potentially harmful chemical in flavoured e-cig vapour. (Getty Images)
  • Research suggests e-cigarette use may have troubling health effects, including a higher risk of heart attack.
  • In 2015, one study found some flavoured vape vapours contain a chemical that's been linked to a condition called "popcorn lung."
  • It's a disease in which the airways become obstructed, and it once happened to a group of workers at a microwave popcorn factory.
  • There's still no definitive evidence that vaping causes popcorn lung, but some experts have called for more research into the potential connection.

As part of a push to minimise e-cigarette use among teens, Silicon Valley start-up Juul announced on Tuesday that it will temporarily pull flavoured e-cigarette pods from retail stores throughout the US.

"As of this morning, we stopped accepting retail orders for our Mango, Fruit, Creme, and Cucumber Juul pods to the over 90,000 retail stores that sell our product, including traditional tobacco retailers (e.g. convenience stores) and speciality vape shops," Juul CEO Kevin Burns said in a statement.

The flavours will return to stores once they agree to adopt the company's new age restrictions and a stronger system to ensure customers are at least 21, Business Insider reported.

The move has been approved by many scientists and public health experts amid growing concerns that e-cigarette flavours make the products especially appealing to young people.

"E-cigs have become an almost ubiquitous - and dangerous - trend among teens," FDA Commissioner Scott Gottlieb said in a statement in September. "The disturbing and accelerating trajectory of use we're seeing in youth, and the resulting path to addiction, must end."

A pamphlet released by the US Surgeon General's office outlines a number of possible health risks tied to e-cigarette use. One of those possible risks, the pamphlet says, is exposure to a flavouring chemical called diacetyl, which has been linked to a condition called "popcorn lung."

The scary-sounding disease was the subject of a flurry of online articles back in 2016, according to Snopes, some of which claimed that e-cigarettes caused popcorn lung. But those claims were exaggerated, and experts say we need more research on the potential relationship between vaping and popcorn lung.

Here's what to know about the condition.

"Popcorn lung" is a nickname for a condition called Bronchiolitis obliterans

Bronchiolitis obliterans (BO) affects the bronchioles, which are the lung's smallest airways, according to the National Institutes of Health Genetic and Rare Diseases Information Centre. In people who have the condition, the bronchioles can become inflamed and damaged, causing scarring that blocks the airways. The symptoms include coughing, shortness of breath, and fatigue or wheezing even in the absence of a cold or asthma.

The National Institute for Occupational Safety and Health describes BO as "a serious lung disease that is irreversible."

It's also known by the nickname "popcorn lung" because, in 2000, the condition appeared in a group of workers at a microwave popcorn factory who inhaled artificial butter flavour. An investigation concluded that there was a link between the extent of the workers' airway damage and their exposure todiacetyl, a chemical used in artificial butter flavouring. (Afterward, many popcorn makers promised to phase out the chemical from their flavourings, the Associated Press reported in 2007.)

One study found diacetyl - a chemical linked to popcorn lung - in the vapour of flavoured e-cigs

Much of the discussion surrounding a potential link between e-cigarettes and popcorn lung appears to trace back to a 2015 study published in the journal Environmental Health Perspectives.

In the study, researchers tested the vapour of 51 flavoured e-cigarettes and detected diacetyl in 39 of them.

It's important to note that the study did not prove that vaping causes popcorn lung. It only showed that some flavoured e-cig vapours contain this chemical. The authors of the paper wrote that their results indicated a need for more research.

"Because of the associations between diacetyl and bronchiolitis obliterans ... urgent action is recommended to further evaluate the extent of this new exposure to diacetyl and related flavouring compounds in e-cigarettes," they wrote.

Right now, according to the non-profit Cancer Research UK, there's still "no good evidence" that vaping causes popcorn lung and there have been no reported cases of popcorn lung in e-cigarette users. A 2017 paper in the journal Toxicology also said that, so far, there are no reported cases of the condition from flavoured e-cigarettes.

But the authors of that 2017 paper also echoed the need for additional study in this area.

"Further research is needed to determine the short- and long-term health consequences of e-cigarettes including risk from diacetyl and similar flavouring constituents," they wrote.

There are other reasons why vaping may be dangerous

For now, any potential link between popcorn lung and e-cigarettes remains unclear. But there are other ways that vaping may harm health.

E-cigarettes do expose users to fewer harmful chemicals than burned cigarettes, according to the Centres for Disease Control and Prevention (CDC), and much of the available evidence suggests vaping is somewhat healthier than breathing in burned tobacco, as Business Insider has reported. There is also some limited evidence that vaping may help people quit smoking regular cigarettes.

But additional recent research suggests that vaping may have its own troubling health effects.

In one study, researchers analysed popular brands of e-cigs (not including Juul) and found some of the same toxic metals (like lead) in these devices that would normally be found in regular cigarettes, Business Insider reported. And in another study, scientists concluded there was evidence linking daily vaping to a higher risk of heart attack.

Most e-cigs also contain nicotine, the addictive chemical also found in cigarettes and other tobacco products. Nicotine can harm the developing teen brain, particularly the parts that control attention, learning, mood, impulse control, according to the CDC.

For now, the agency says, using any tobacco product, including e-cigs, is "unsafe for young people."

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