[pergadad]

Many farms are near polluted places - especially airports and big streets where people wouldn't want to live. So you won't really escape the pollution - but maybe the chance of eating car exhausts is better than the guarantee of eating them. Then again, you don't know what else happened with processed/supermarket food before it reaches you.

[gruez]

I think you have it backwards. The more accurate statement is that farms are everywhere, including near airports and big roads. It's not like farms cluster around major highways or airports. I would even go as far to say that your average farm plant sees less road pollution than a similar plant in a suburban environment.