The worst affected countries are the Andean countries (Ecuador, Peru and the Plurinational State of Bolivia), some Central American countries and Haiti. As a result, over 100 million people in the region are exposed to air pollution levels that exceed WHO recommended limits (Cifuentes and others, 2005), which causes serious health problems. Particulate emissions, including precursors such as sulfur dioxide and nitrogen oxides, have various points of origin. Transportation is the main source of pollution, both directly and indirectly by loosening and stirring up dust. Paving roads, reducing sulfur content and making cleaner fuels, implementing vehicle inspection systems and modernizing the automotive fleet are some steps in the right direction for resolving these problems, but they must be strengthened. The truck and bus fleet is very old and poorly maintained and growing congestion is increasing emissions, production losses and other externalities.