born 1950 292 → 10 µg/m³ in december 1952 a smog killed about twelve thousand people in five days. the clean air act followed in 1956. the air is about fifty times cleaner than victorian london.
method annual mean smoke (pre-1990) and PM2.5 (post-1990) in µg/m³, harmonised approximately from Fouquet 2011, Brimblecombe 1987 and DEFRA/LAQN.
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