The Food and Drug Administration on Friday authorized the first menthol-flavored electronic cigarettes for adult smokers, acknowledging that vaping flavors can reduce the harms of traditional tobacco smoking.

The FDA said it authorized four menthol e-cigarettes from Njoy, the vaping brand recently acquired by tobacco giant Altria, which also sells Marlboro cigarettes.

The decision lends new credibility to vaping companies’ longstanding claim that their products can help blunt the toll of smoking, which is blamed for 480,000 U.S. deaths annually due to cancer, lung disease and heart disease.

Parent groups and anti-tobacco advocates immediately criticized the decision, which comes after years of pushing regulators to keep menthol and other flavors that can appeal to teens off the market.

“This decision could mean we’ll never be able to close the Pandora’s box of the youth vaping epidemic,” said Meredith Berkman, co-founder of Parents Against Vaping E-cigarettes. “FDA has once again failed American families by allowing a predatory industry to source its next generation of lifetime customers — America’s children.”

Youth vaping has declined from all-time highs in recent years, with about 10% of high schoolers reporting e-cigarette use last year. Of those who vaped, 90% used flavors, including menthol.

All the e-cigarettes previously authorized by the FDA have been tobacco, which isn’t widely used by young people who vape.

Njoy is one of only three companies that previously received FDA’s OK for vaping products. Like those products, the menthol varieties come as cartridges that plug into a reusable device that heats liquid nicotine, turning it into an inhalable aerosol.

Njoy’s products accounted for less than 3% of U.S. e-cigarette sales in the past year, according to retail data from Nielsen. Vuse, owned by Reynolds American, and Juul control about 60% of the market, while hundreds of disposable brands account for the rest.

Most teens who vape use disposable e-cigarettes, including brands like Elf Bar, which come in flavors such as watermelon and blueberry ice.

Altria’s data showed Njoy e-cigarettes helped smokers reduce their exposure to the harmful chemicals in traditional cigarettes, the FDA said. The agency stressed the products are neither safe nor “FDA approved,” and that people who don’t smoke shouldn’t use them.

Friday’s action is part of a sweeping FDA review intended to bring scientific scrutiny to the multi-billion dollar vaping market after years of regulatory delays. Currently the U.S. market includes thousands of fruit- and candy-flavored vapes that are technically illegal but are widely available in convenience stores, gas stations and vape shops.

The FDA faced a self-imposed court deadline at the end of this month to wrap up its yearslong review of major vaping brands, including Juul and Vuse.

Those brands have been sold in the U.S. for years, awaiting FDA action on their scientific applications. To stay on the market, companies must show that their e-cigarettes provide an overall health benefit for smokers, without significantly appealing to kids.

“Based upon our rigorous scientific review, in this instance, the strength of evidence of benefits to adult smokers from completely switching to a less harmful product was sufficient to outweigh the risks to youth,” said Matthew Farrelly of FDA’s Center for Tobacco Products.