OVER THE past several years, the e-cigarette business has boomed, tying public-health experts in knots. On one hand, the devices are far less dangerous than conventional cigarettes. It would be a public-health victory if every smoker stopped lighting up and chose to vape instead. On the other hand, e-cigarettes seem designed to appeal to children and teenagers. E-cigarette liquids come in a variety of candylike flavors that, according to federal health officials, have driven interest among young users. Some young people — it is unclear how many — would not have gotten hooked on nicotine without e-cigarettes.

As youth e-cigarette use jumped900 percent between 2011 and 2015, according to federal officials — the federal government hardly reacted. Astonishingly, there has been no ban on selling e-cigarettes and vaping liquids to minors, let alone consistent regulations on packaging, labeling and advertising or professional review of the ingredients that vaping companies put in their products. Though these products doubtless are less harmful than conventional cigarettes, they certainly contain nicotine, which may harm adolescent brains, and they might contain other chemicals that pose health dangers. The risks associated with inhaling secondhand vapor are also unknown.

This regulatory vacuum has been unnecessary. Under the Tobacco Control Act, the Food and Drug Administration has wide-ranging power to regulate tobacco products. The agency finally has decided to begin using it more fully, announcing a final rule on e-cigarettes, cigars and hookahs. The rule bans e-cigarette sales to minors and requires sellers to check buyers’ ages but stops short of cracking down as hard as the FDA could, by banning certain flavorings, for example. The most controversial part of the rule requires e-cigarette and e-liquid makers to submit their products to extensive FDA review before sale, providing ingredient lists and any data they have on health effects.

Critics castigated the agency for cracking down on a young industry filled with small operators. The result, they say, will be more expensive and less desirable e-cigarette products, which will drive up conventional smoking and reward big tobacco companies that can afford to navigate the FDA process. This view neglects the danger that e-cigarette use will become increasingly common among youths, who without regulation would assume the products were safe, addicting a generation of children and teens to nicotine.

E-cigarette businesses, whether small or large, are mixing highly addictive batches of chemicals and selling them with almost no federal oversight. Figuring out what is in these products is necessary for figuring out how dangerous they are — and how to make safer nicotine delivery devices for those trying to quit conventional smoking.

The FDA’s e-cigarette rules do not overreach. They are long overdue.