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 : Achim Steiner , executive director of the United Nations Environment Program , says plastic bags are the second-most-common form of litter , behind cigarette butts . Plastic bags are second-most common form of litter . Score: 7
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 . Score: 7