Does Mexico City have more pollution than Birmingham England?

Answer 1

It would depend on time of the year and area, as both cities are big urban conglomerates where air pollution tends to vary according to specific areas within the city. Nowadays, the Air Quality Index (or PM10) measures particles suspended in the air; the higher the value the more polluted it becomes.

For May 11th 2005, air pollution in Birmingham is moderate, with a maximum Air Quality Index of 75 (Birmingham downtown) and a minimum of 89 (Tyburn). Both numbers would qualify as "Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution."

Same measurements for Mexico are 112 (Camarones) and 78 (Pedregal). It seems Camarones, to the northwest of the city, is the most polluted, whereas that 112 means "Members of sensitive groups may experience health effects. The general public is not likely to be affected."