You're right that the average air above London is often (not always) pretty clean compared to the world's most polluted cities. Right now I can look out my wind

You're right that the average air above London is often (not always) pretty clean compared to the world's most polluted cities. Right now I can look out my window and clearly see buildings that are several km away. Today, at least, there is very little visible haze. But the real problem is London's narrow, busy streets with heavy motor vehicle traffic in very close proximity to where Londoners live, work, walk, go to school, etc. Anyone who spends much time in Central London is spending a significant portion of their lives in close proximity to the exhaust fumes from thousands of vehicles daily, so exposure to toxic pollutants in London is much worse than many measures of average air quality suggest! On the bright side, there has been a noticeable improvement recently thanks to initiatives like the Central London ultra-low emission (ULEZ) zone, and the increasing numbers of electric taxis replacing the old diesel ones. One major area that still needs improvement is the buses - there are now some electric buses, but still far too many old, polluting diesel ones.