In many developing countries, the absence of surface-based air pollution sensors makes it difficult to get even a rough estimate of the abundance of a subcategory of airborne particles epidemiologists think contribute to millions of premature deaths each year, researchers at the NASA/Goddard Space Flight Center say.
The problematic particles, called fine particulate matter or PM2.5, are 2.5 micrometers or less in diameter, about a 10th the width of a human hair. These small particles can get past the body's normal defenses and penetrate deep into the lungs.
Researchers Aaron van Donkelaar and Randall Martin at Dalhousie University in Nova Scotia used data from two NASA satellites, combined with computer models, to create a world map of the distribution of PM2.5 particles.
Their map, which shows the average PM2.5 results between 2001 and 2006, offers the most comprehensive view of the health-sapping particles to date. It has provided the first PM2.5 satellite estimates in a number of developing countries that have had no estimates of air pollution levels until now, they say.
The map shows high levels of PM2.5 in a broad area stretching from the Sahara Desert in Northern Africa to Eastern Asia. When compared with maps of population density, it suggests more than 80 percent of the world's population breathe polluted air exceeding the World Health Organization's recommended level of 10 micrograms per cubic meter.
"We still have plenty of work to do to refine this map, but it's a real step forward," Martin said. "We hope this data will be useful in areas that don't have access to robust ground-based measurements."