Believe it or not, smog in US cities used to be a lot worse. In fact, at the height of the Second World War, residents of Los Angeles thought they were under a chemical gas attack. People in the downtown area experienced stinging eyes, streaming noses, and rasping throats, all due to a haze of pollution that covered the city. Thanks to clean air regulations, America’s air has gradually gotten better over the past few decades. Last year, a study of researchers at Yale University estimated that the annual air pollution deaths in the US dropped by almost half between 1990 and 2010 due to environmental improvements. A separate study looked at the cost and benefits for the Clean Air Act, which was highly criticized for “stifling economic growth” through its restrictions. Yes, the Clean Air Act imposed a cost on industry; around $65 billion, but it produces a health benefit of around $2 trillion. For each dollar invested, the US gained thirty-one dollars in return. While industry leaders may balk at restrictions, the result of such regulations not only save Americans trillions in health costs, but they also make our cities much more livable.