Flavoured e-cigarettes have been blamed for an increase in vaping among teenagers and young adults.Credit: Spencer Platt/Getty

An outbreak of deadly lung injuries in vapers in the United States — many of them adolescents — shows no signs of stopping. So far, 805 e-cigarettes users have fallen ill, 12 of whom have died. The illnesses are fuelling a push among lawmakers and regulators to rein in the sale of e-cigarettes, in particular those with flavours that could be contributing to a worrying surge in youth vaping.

It’s illegal for vendors in the United States to sell e-cigarettes to those younger than 18; in some states and cities, the age limit is 21. Yet more than a third of the sick vapers are younger than 21, according to the US Centers for Disease Control and Prevention (CDC).

Public-health officials have yet to find a definitive cause for the lung injuries, according to the CDC. And they worry that some of the affected adolescents might never fully recover. But it’s unclear what impact, if any, the new restrictions on e-cigarette sales will have on the health crisis or the problem of youth vaping.

Nature takes a look at the issues.

What exactly are US regulators and lawmakers doing?

In response to the recent spate of lung injuries, the US Food and Drug Administration (FDA) — which regulates tobacco products including e-cigarettes — announced on 11 September that it plans to remove flavoured devices from the market, at least temporarily.

The decision came as the agency was already seeking to regulate e-cigarettes after years of lax enforcement. Under FDA regulations, e-cigarette manufacturers must apply for agency approval to market their products. So far, none of the companies has submitted an application, but the FDA has nevertheless allowed their devices to stay on the market. The agency has given manufacturers until May 2020 to submit applications to continue selling their products.

Some states aren’t waiting for the federal government to act. In response to the recent surge in lung injuries and deaths, New York, Michigan and Rhode Island banned sales of flavoured e-cigarettes last month. And on 24 September, Massachusetts declared a four-month halt on the sale of all e-cigarettes.

Why the focus on flavour?

Public-health officials have long suspected that e-cigarettes with flavours based on fruit or sweet snacks such as ’cupcake’, ‘bubble gum’, and ‘apple crack’ are designed in particular to appeal to young people. Most adolescents report that flavoured e-cigarettes were a key reason they took up vaping, said Anne Schuchat, deputy director of the CDC during testimony before the US House of Representatives on 24 and 25 September. “We’re extremely concerned about flavours and the role that they play in hooking young people to a life of nicotine.”

Data from a national survey1 published in the New England Journal of Medicine on 18 September showed that adolescent vaping in the United States more than doubled from 2017 to 2019. More than one-quarter of US high-school seniors, typically 17–18 years old, reported vaping at least once in the previous 30 days.

Does anyone think flavoured vapes should stay on the market?

Some tobacco-control researchers worry that banning flavours could deter adults from using e-cigarettes in attempts to quit smoking. Seventy to eighty per cent of adults say that using flavoured vapes was crucial to their smoking-cessation efforts, says David Abrams, a behavioural scientist at New York University. “You don’t want something that reminds you of your old cigarette taste or smell,” he says.

But the CDC says that adult vapers are more influenced by the nicotine content of an e-cigarette than by its flavour. And despite the fact that many people use e-cigarettes to help them quit smoking, there’s little evidence that they are more effective than other tools, said Schuchat at the Congressional hearing.

Could the flavours themselves themselves be dangerous?

It’s unclear. Some chemicals used to flavour e-cigarettes might be toxic, and it’s possible that they can damage the lungs, says Albert Rizzo, chief medical officer of the American Lung Association in Chicago, Illinois. One 2016 study2 of 51 e-cigarette flavours found that 39 of them contained diacetyl, an additive linked to lung damage.

Another study3, published in February, found that some vaping liquids were up to 34% cinnamaldehyde, a chemical that can kill lung cells. “When you get to levels like that of a compound like cinnamaldehyde, having some lung difficulties isn’t very surprising,” says study co-author James Pankow, a chemist at Portland State University in Oregon.

These analyses focused on the liquids that e-cigarettes heat and turn into a vapour that users breath in. The liquids come in cartridges that vapers can swap out of their devices. But that heating process changes the chemical composition of the liquid, says Mignonne Guy, a biobehavioural researcher at Virginia Commonwealth University in Richmond. And scientists are still struggling to identify all the chemicals in the vapour. The plethora of devices and user modifications available to consumers results in a complex array of heating conditions and liquid concentrations that complicates the researchers’ task.

Will removing flavours from the market reduce youth vaping?

Although numerous studies have shown that young people are attracted to flavoured e-cigarettes4, there’s no data yet on what would happen to the number of teenage vapers if officials removed these devices from the market, says social scientist Jessica Pepper of RTI International, a non-profit research group in Research Triangle Park, North Carolina.

Banning flavoured e-cigarettes could also drive demand to the black market, Guy says. She supports the move to pull the devices from the market. But Guy says that as long as refillable e-cigarette cartridges exist, vapers will be able to mix their own liquid and include flavouring chemicals.

What other approaches could reduce youth vaping?

Lawmakers have proposed eliminating online sales of e-cigarettes to make it more difficult for adolescents to buy the products. And the FDA has launched an educational programme to inform young people about the risks of vaping.

But some lawmakers are pushing for more drastic measures. These include a ban on all e-cigarettes until manufacturers demonstrate that the benefits of using the devices — such as help for people who want to quit smoking cigarettes — outweigh the risks.

“How many children are we going to allow to die before this is considered the emergency it is and we just say no?” asked Jan Schakowsky, Democratic representative from Illinois, at the congressional hearing on 25 September. “We should be saying, ‘no’ right now.”