Fighting air pollution in the US is not a solved problem. There's been tons of advancement, which certainly includes the development of technologies and techni

Fighting air pollution in the US is not a solved problem. There's been tons of advancement, which certainly includes the development of technologies and techniques that can readily be deployed elsewhere. Major population centers like Los Angeles and San Francisco have certainly reaped benefits from industrial and transportation regulations over past decades. The smog is less dense, less harmful, and has more appealing colors. However, it still exists, does cause harm, and needs constant attention to make sure it doesn't get worse. There's still a ton that can be done.