pBy Susana Ferreira/ppPORT-AU-PRINCE (Reuters) - Haiti imposed a ban on plastic and foam food containers as well as black polyethylene bags on Monday, amid concern that the countrys poorest consumers would not be able to afford the substitutes./ppThe ban is the first in a series of government measures aiming to help the environment of the poorest country in the hemisphere. a href=http://www.scientificamerican.com/article.cfm?id=haiti-plastics-ban-gets-mixed-react[More]/a