I’ve lived in a couple of cities in Europe and I can tell you my nose was runny far more often in a poluted place like London (UK) than it is in the small city I live in now in Portugal or the places I lived in when in The Netherlands.

I suspect that the tendency to catch colds and suffer from alergies is often coupled with all the Sulfur Oxide gases around in cities with lots of car polution which turn into various sulfur oxiacids when those gases mix with water in the nose and airways.