It's all Obvious, Mr.

Research for yourself.

https://duckduckgo.com/?q=first+killing+smog+in+london%3F&t=h_&ia=web

https://theculturetrip.com/europe/united-kingdom/england/london/articles/a-brief-history-of-london-fog/

London’s basin location in the Thames estuary had always made it prone to natural mist, with moisture becoming trapped by the surrounding hills; but coal smoke combined with natural fog to create a ‘pea-souper’, a thick smog that could last for days. London’s troubles with smog persisted right through the 1800s — the very term ‘smog’ was coined by an oxygen-starved Londoner in 1905.

In 1873 came the first unusually thick and persistent fog, which caused at least 268 deaths from bronchitis. In 1879, a fog lasted for four whole months, but still no reform was passed — at the height of the coal-fuelled industrial revolution, there was no alternative with which to power progress.

Then, in 1952, a four-day fog dubbed The Great Smog hit amid a perfect storm of weather conditions, causing major disruption in transport. Every transport service apart from the London Underground ceased (including emergency services) due to a horrendous level of visibility — indoor performances were abandoned when the smog seeped indoors, blocking cinema screens and stages from view. Though smog-weary Londoners didn’t panic at first, weeks later 4,000 Londoners were found to have been killed, with 100,000 more made seriously ill, thereby forcing parliament to act (the number killed is now estimated to be closer to 12,000). In 1956 they passed the Clean Air Act, introducing smoke-free areas in cities, limiting the burning of coal and offering households incentives to install gas fires.

Look Familiar?