I was out at dawn this morning cleaning my car windows (with the drought conditions here is SoCal i have not washed my vehicle in months). I believe that all the crud and dirt on the windows was deposited there by dew, no roof runoff, etc. I think I would boil before imbibing.

I an right on the coast,but rain reaches us from the west or northwest, and probably does pick up some pollution, but I imagine it is even worse further inland.