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Flavored Juul ingredients combust to create toxic chemicals that are NOT listed on the label

People who smoke flavored Juul pods inhale toxic chemicals that do not appear on the label, according to new research.  

The listed ingredients for flavors such as Creme Brulee and Cool Cucumber are: ‘vanillin’, a flavorant, glycerol, propylene glycol, nicotine, and benzoic acid.  

But chemical engineers at Yale University have found that, when heated, these chemicals combust to create acetals, an unexpected, dangerous byproduct that irritates the lungs.

What’s more, around 60 to 70 percent of those acetals transfer into the vapor that users inhale. 

Researchers found acetals, a toxic byproduct, in both the e-liquids and the aerosol of flavored Juuls. In their tests, they found most of the acetals were created by a reaction with glycerol

‘People often assume that these e-liquids are a final product once they are mixed,’ lead author Hanno Erythropel said. 

‘But the reactions create new molecules in the e-liquids, and it doesn’t just happen in e-liquids from small vape shops, but also in those from the biggest manufacturers in the US.’

An estimated 2.2 million Americans use e-cigarettes, the majority of whom use Juul, a sleek device that looks like a USB. 

The company started in 2015, but it wasn’t until 2017 when business really started to take off. 

Now, the company is valued at an estimated $16 billion – but its meteoric rise, particularly among teenage consumers, has made it a bulls-eye for regulators, researchers and health officials. 

To make matters complicated, there is not yet enough evidence to concretely quantify the risks. 

But a growing swell of research shows there is cause for concern. 

The Yale team, working with researchers at Duke University, zeroed in on flavored Juul pods, since those have been such a hit among young people. 

Using a ‘vaping machine’, they analyzed the chemical transformation that occurs, to get a stronger idea of what, exactly, one inhales when they take a drag on a Mango Juul, for example. 

First, said co-author Sven-Eric Jordt of Duke University, they were struck by how much vanillin is in each flavored Juul pod. 

The flavorant is not explicitly dangerous in small quantities, but industries that use it – such as industrial bakeries and fragrance manufacturers – have a limit on how much they can use and be exposed to.  

Juul pods sit just below that borderline. 

‘We were surprised that levels in Juul vapor were already close to safety limits for workplaces where vanillin is used, such as in bakeries and the flavor chemical industry,’ Jordt said.

The most striking finding, though, was the acetals, found both in the e-liquids and the aerosol. 

And in their tests, they found most of the acetals were created by a reaction with glycerol. 

Reacting to the findings, Thomas Ylioja, PhD, of National Jewish Health, told, said it is yet more evidence that we are still very ignorant about e-cigarettes.

‘What it really does is tell us that we are still finding out potential harmful effects of electronic cigarette use which is concerning for teens using that and are hearing that those products might be safe for them,’ Dr Ylioja, a smoking cessation expert who was not involved in the study, said. 

‘The chemical compounds of those liquids when they are heated up change.

‘We are really concerned about the flavors because that’s one of the biggest ways teens are exposed. 

‘They are not harmless products. They are not safe to use.’ 

Juul has not yet responded to’s request for a comment. 


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