We've already made huge strides in this. Here's [0] a gallery of shots of LA smog in the middle part of the last century. It's full of pictures of people crying because the air pollution is stinging their eyes. It's nearly unthinkable today, aside from the random winter day in Salt Lake where an inversion traps everything. But it was a daily occurrence back then!

[0] http://www.latimes.com/local/la-me-air-pollution-0428-pictur...