By Chris Kirkham (Reuters) – The U.S. Food and Drug Administration and Customs and Border Protection seized more than $18 million worth of unauthorized e-cigarettes, which included popular brands such as Elf Bar, the FDA said on Thursday. About 1.4 million units were confiscated in a joint three-day operation in July at a cargo examination site at Los Angeles International Airport, according to the FDA. Elf Bar was the most commonly used brand among youth e-cigarette users, with 56.7% of middle- and high-school vapers naming it their brand of choice, according to a national survey of youth tob…