the United States is the Western Hemisphere second large metro area to ban the bags . Move comes as leading environmentalists call for global ban . CNN agency : Plastic bags are second -most common form of litter . Bags a major threat to ocean wildlife , U.N. agency says .
Mexico City is Western Hemisphere 's second large metro area to ban the bags . Move comes as leading environmentalists call for global ban . U.N. agency : Plastic bags are second-most common form of litter . Bags a major threat to ocean wildlife , U.N. agency says .