Everyone "knows" that China is badly polluted. I've written over the years, and still believe, that environmental sustainability in all forms is China's biggest emergency, in every sense: for its people, for its government, for its effect on the world. And yes, I understand that the same is true for modern industrialized life in general. But China is an extreme case, and an extremely important one because of its scale.
Here are two simple charts, neither of them brand-new but both easily comprehensible, that help dramatize how different the situation is there. The first, by Steven Andrews for China Dialogue via ChinaFile, compares official Chinese classifications of "good" air conditions with those in Europe or North America.
Here is the point of this graphic: The green and yellow zones in the left-hand column, showing official Chinese government classifications, are for "good" or "OK" air—while those same readings would be in the danger zone by U.S. or European standards. When you're living in China, it's impossible not to adjust your standards either to ignore how dire the circumstances are, so you can get on with life, or to think that any day when you can see across the street is "pretty good."