But that’s what always happened. I would be more concerned of living next to a heavy industrial city or country like Shanghai or New Delhi, sometimes even a single concrete production factory can affect sensible people like asthmatic (as it happened to me for a short time of my life). Same story for landfills, or agriculture regions which have the tradition to burn rests from their activity causing serious air saturation.
As said I would be more concerned of other factors, including pollution, general climate, time to nature and sustainability of the city for a good work life balance. And king would be: time to commute work.