Many of us never got to experience it, but the air quality in LA in the ‘40s  ‘50s, ‘60s, and ‘70s was deadly. Smog hung in the air like a thick fog and many residents actually said that it hurt to breathe.

Sources:

https://www.kcet.org/history-society/how-los-angeles-began-to-put-its-smoggy-days-behind

https://earther.gizmodo.com/environmental-regulation-has-helped-cut-deaths-from-air-1829875441

https://www.hemmings.com/magazine/hcc/2007/09/After-Burner/1509192.html  

https://www.marketplace.org/2014/07/14/sustainability/we-used-be-china/la-smog-battle-against-air-pollution

https://www.geek.com/geek-cetera/spaceballs-becomes-reality-canadian-company-is-selling-bottled-air-to-the-chinese-1642442/

https://www.cnbc.com/2015/12/15/canadians-are-selling-cans-of-fresh-air-to-china.html

http://www.bbc.com/capital/story/20170515-the-entrepreneurs-making-money-out-of-thin-air

https://www.cnn.com/2016/02/08/world/fresh-air-britain-china-bottles/index.html

https://ww2.arb.ca.gov/about/history