how much air pollution is in an average city

Question: how much air pollution is in an average city
- Keywords:
  air,
  average,
  city,
  pollution
Asked by anon-177559 to Daniel on 11 Jun 2018.
- Daniel Marsh answered on 11 Jun 2018:
  
  There is no such this as an avergae city, London would produce a very different amount of pollution compared to Beijing, Cairo or Mexico City to name a few!

Question: how much air pollution is in an average city