In 2007-2008 at least 27 cities in the region —including 10 capitals— exceeded the particulate matter (PM10) limits recommended by WHO. At least 100 million people in Latin America and the Caribbean are said to be exposed to air pollution at levels that exceed WHO-recommended limits (Cifuentes and others, 2005). The groups most vulnerable to the effects of air pollution are children, the elderly, people with certain pre-existing health conditions and those in poverty. In a period of around four years from 2004 to 2008, less than a third of the countries (seven of 24) were able to reduce the number of deaths from causes related to air pollution.