I think people underestimate the impact of air pollution because it's so easy to get desensitized to it. Try wearing a respirator with good seal and filter in a

I think people underestimate the impact of air pollution because it's so easy to get desensitized to it. Try wearing a respirator with good seal and filter in an urban area for 10 minutes or so. When you take it off you'll probably smell vehicle exhaust you didn't notice before. Human sense of smell tends to tune out constant low level background odors, but they can still be a sign of something harmful.