(AP) Governments should have tougher rules for electronic cigarettes — banning their use indoors and putting them off limits for minors — until more evidence can be gathered about their risks, the U.N. health agency said Tuesday. In a bid to set public policy, the World Health Organization said the popular nicotine-vapor products, particularly the fruit, candy and alcohol-drink flavors, could serve as gateway addictions for children and adolescents. It recommended governments forbid or keep to a minimum any advertising, promotion or sponsorship in a market that has mushroomed to $3 billion last year and now includes 466 different brands. Little is known about the health effects of e-cigarettes, which have been sold in the U.S. since 2007. U.S. regulators in April proposed treating e-cigarettes as tobacco products with rules such as a ban on sales to those under 18 and warning labels.