Air pollution has reached appalling levels in China, the world’s biggest carbon emitter. But we all knew this was coming and should not be surprised.

The Chinese economy has grown spectacularly by following models of advanced economies. Economic catch-up can be a matter of choosing what and when from a proven menu, though too often that approach underestimates the costs connected to a particular development tool. It was known, for instance, that allowing the use of cheaper gasoline with high sulfur content to reduce automobile operating costs and increase car sales would lead to severe air pollution.

Xie Zhenhua, vice chairman of the National Development and Reform Commission, China’s top economic planning body, admits that pollution is harming the mental and physical health of the nation’s citizens, that China has an “obsolete development model” with an “unreasonable industrial and energy structure.” Yet China, putting economic growth as its foremost goal, has consciously pursued an obsolete model with all the known downsides. It unwisely acted as if environmental degradation is an unavoidable byproduct of economic growth.

Mr. Xie says that China will see improvement in air quality in about 5 to 10 years. China is only now belatedly beginning to adopt the kind of environmental policies that worked for advanced economies more than a generation ago.