This post originally appeared on State of the Planet, the Earth Institute's blog.

Air quality matters for human health, and many of the world’s urban areas suffer from high levels of contamination. One of the worst pollutants is PM_2.5., which are microscopic particles less than 2.5 microns in diameter that lodge deep in the lungs, potentially leading to respiratory and cardiovascular disease in exposed populations. According to World Health Organization research on the environmental burden of disease, outdoor air pollution causes close to one million premature deaths worldwide each year, with particulate matter as one of the leading contributors. Fine particulates originate in large part from fossil fuels combustion and from agricultural and forest fires. MORE 

In the end, we determined that it was not possible to produce an aggregate index by province–but the process revealed the steps that would be necessary to fulfill that vision.

Given China’s burgeoning economic growth, rapidly expanding industries, large population and growing consumer class, many in the environmental field have an intense interest in how the nation will address its environmental problems. The country has made some impressive energy and resource efficiency gains, and environmental issues are an important part of the government’s efforts to build a “harmonious society.” MORE 

Beijing’s air quality dominated international headlines when discrepancies arose last October between official monitoring data and U.S. Embassy measurements.

Pictures of stifling haze and smog posted and circulated online by netizens depicted extreme pollution. The U.S. Embassy’s monitor indicated that the air quality was “hazardous” and “beyond index, but “the Chinese government’s official Air Pollution Index indicated that the air was only “slightly polluted.[1]” MORE