Not OP, but anecdotally— I grew up in a small town (Pop ~5000, now ~6000) in rural Ontario, Canada. I live in the city now. Whenever I visit home I can taste h

Not OP, but anecdotally— I grew up in a small town (Pop ~5000, now ~6000) in rural Ontario, Canada. I live in the city now. Whenever I visit home I can taste how much sweeter the air is. The difference is palpable— especially in areas where there is limited medium/heavy industrial production and more agriculture and wilderness.