Thread by @jimmcquaid

5th December 1952 marked the start of the horrific Great Smog of London. The smog triggered the process that led to the Clean Air Act in 1956. During the following 5 days, 4000 lives were lost followed by a further 8000 in the following weeks. 1/n

https://twitter.com/BBCArchive/status/1731938960262209561

During the day on 5 December, the fog was not especially dense and generally possessed a dry, smoky character. When nightfall came, however, the fog thickened. Visibility dropped to a few metres. The following day, the sun was too low in the sky to burn the fog away. 2/n

In The Isle of Dogs area, the fog there was so thick people could not see their feet!
The smoke-like pollution was so toxic it was even reported to have choked cows to death at Smithfield market. 3/n

Whilst very difficult to quantify, the long-term impact of breathing in sulphuric acid probably impacted the health/lifespan of tens if not hundreds of thousands of Londoners. 4/n

The main driver of the smog was a very stable temperature inversion with very light winds which trapped the air very close to the surface, meaning the smoke just built up and up 5/nmetoffice.gov.uk/weather/learn-…

At the time the high value coal (anthracite) was being exported to pay off the war debts whilst high sulphur (lignite) was burnt by the residents of London, producing a toxic soup 6/n

These days, it is thought that domestic burning (for secondary heating, rather than primary heating as it was in the 1950's) is a significant source of PM2.5 particles, with levels increasing by over 100% btwn 2011 and 2021 7/7cieh.org/news/press-rel…