The World Health Organization (WHO) says 92 percent of the world's population breathes air containing pollutants exceeding the United Nations health body's recommended limits.

"Air pollution continues take a toll on the health of the most vulnerable populations - women, children and the older adults," WHO assistant director general Flavia Bustreo said in a news release.  "For people to be healthy, they must breathe clean air from their first breath to their last."

WHO's air-quality model uses satellite data and ground measurements to gather "the most detailed outdoor (or ambient) air pollution-related health data, by country, ever reported".  These measurements of "sulphates, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water" are taken from nearly 3,000 places from around the world.  That's double the amount of data compared to the previous WHO assessment of this kind.

The organization says three million deaths a year are linked to exposure to outdoor air pollution, and nearly 90 percent of air-pollution-related deaths occur in low- and middle-income countries.  It puts these people at higher risk of heart disease, strokes, and cancer. 

China had the most deaths attributable to air quality in 2012, at 1,032,833; that's followed by 621,138 in India; and 140,851 in Russia.