A friend of mine just sent me this map of air pollution in San Francisco from the San Francisco Chronicle.
Using the latest PM2.5 data, I created a map for China using the same scale:
But I shouldn’t mock people for being worried about pollution. America’s PM2.5 levels are way lower than China’s, but studies in the US have still found those lower levels are harming our health.
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.