A nice day in Europe will see pollution levels of 5k-20k particles/l. EU guidelines recommend not exercising outdoors if levels reach 105k particles/l.
A company in Eastern HK (the supposedly cleaner side), on an average day, measured 800k particles/l, indoors and outdoors. Air-conditioning on/off had no effect whatsoever.
These are micro-particles that enter the bloodstream and can cause chronic diseases.
Explain to your kids when they get lung cancer at 40 that you thought it was worth it for the money.