Open sharing of pollution data helps Chinese netizens brave the politics of murky air.

IT IS obscure. It is scientific jargon. But to Chinese urbanites, PM2.5 is now as ubiquitous as tea. The term refers to airborne particles—from vehicle exhaust and from burning wood and coal—that are so small, several thousand could perch snugly on the pointy end of a sesame seed. These tiny particles can slip into your lungs and blood stream and aggravate heart disease and other illnesses. When PM2.5 levels in the cities rise, the chatter on Weibo, the Chinese version of Twitter, swells. Case in point: when concentrations rose to hazardous levels in Beijing on January 12, 2013, there were nearly 40 million messages on “pollution” and “PM2.5.”

“The term is technical and wonky,” said Angel Hsu, who studies Chinese environmental policy at Yale University. “But Chinese citizens have become very aware of air pollution issues, specially those involving fine particulate matter. I even saw an ad for a rock music festival called PM2.5.” Because of the extremely bad air days in Beijing, residents, visitors, scientists, and policymakers are discovering that open access to air quality data could help warn people when everyone—children, the elderly and even healthy adults—should stay indoors because of dangerous pollution. The data are crucial in the dialogue between citizens and the government in cleaning up the air for years to come. Hsu said it all began in early October 2010 when Beijing residents looked out their windows and saw not the city’s cosmopolitan skyline, but something that looked like a whole lot of wu.

Originally published in Sensing Our Planet: NASA Earth Science Research Features. Read the full story here.