Also, if it's polluted outside, isn't it polluted inside too? Do these cities all have buildings with air purifiers?
Also, particulate matter is much more volatile outdoors, because it's outdoors.
And, the downmods, two in a row, make zero sense. Else, explain it please.
Also, if it's polluted outside, isn't it polluted inside too? Do these cities all have buildings with air purifiers?