they could just give their environmental regulators the authority to enforce their existing environmental laws.
In the film Under the Dome, Chinese journalist Chai Jing astonishes a Chinese audience with a film clip from California where Cal DoT stops a truck and actually checks that it has all the mandatory safety and emissions equipment. That never happens in China. China has tough emissions standards on paper, but the law is written so that the regulators don't have any enforcement powers. So Chinese manufacturers simply slap stickers on vehicles claiming they have all the mandatory emissions equipment without installing any of it. Technically this is a crime, but the law's written so there's literally nothing anyone can do about it.
And if you don't think environmental regulations make a difference, this is what New York looked like in 1970. Note that that isn't a sepia tinted black and white photo, it's true color. Granted it shows an exceptionally bad day, but before the Clean Air Act got strengthened in the mid 70s bad smog was pretty common. If you look at pictures of American cities from the 70s you'd think that photo technology of the day put a blue or yellow haze on stuff in the distance (like this). It wasn't the film, cities actually looked that way a lot of the time.
Predicting bad pollution days isn't "fighting" pollution, it's living with it. If you want to fight pollution you've got to stop people from polluting. You've got to catch them at it, fine them, and in some cases throw them in jail. Pollution like they have in China is nothing short of manslaughter on a national scale. 1.6 million people die every year from it.