Air quality across the world has reached toxic levels, and although much publicity is given to Beijing’s life-threatening air, London is even worse with 197 micrograms of particulate per cubic metre, almost enough to eat it:
https://www.naturalnews.com/2017-02-15-air-quality-across-the-world-has-reached-toxic-levels.html
The World health organisation recommends that particular matter in the air stay below 25-50 micrograms per cubic litre in a 24 hour period, but 92 percent of the world’s population live in areas where this air quality is not met:
http://www.who.int/mediacentre/factsheets/fs313/en/
