As vaping continues to be popular among young people, what potential harms could they be exposed to, and when is it time to worry? WASHINGTON — Vaping company Juul Labs on Friday received federal permission to sell an updated version of its e-cigarette, which includes an optional age-verification system designed to prevent underage use.The decision from the U.S. Food and Drug Administration allows the company to sell a new version of its top-selling vaping device for the first time since it launched more than a decade ago. In recent years, the company has had to lay off hundreds of employees…