The Food and Drug Administration authorized Juul e-cigarettes for the U.S. market on Thursday, ending a lengthy standoff with regulators and lawmakers who accused the company of spurring an epidemic of e-cigarette use among youths.

The company was required to prove that the products were “appropriate for the protection of public health” under agency rules. Juul said in a statement that it met the bar, in part, by showing that its products had helped about two million adults quit smoking cigarettes.

The F.D.A. authorized both the e-cigarette system and menthol- and tobacco-flavored cartridges. Though concerns about the health effects of e-cigarettes are mounting, they are still widely viewed by experts as safer than cigarettes.

“Today’s F.D.A. authorization of Juul products marks an important step toward making the cigarette obsolete,” K.C. Crosthwaite, the company’s chief executive, said in a statement.

Mr. Crosthwaite said underage use of Juul products was “down 98 percent since 2019, to one-half of 1 percent of youth.”

At least one lawmaker panned the decision. Senator Dick Durbin, Democrat of Illinois, recounted in a statement Thursday that Juul had “ignited” an epidemic of vaping among youths and “lied about the harms of their vapes.”