chockablock investigated that here on HN, at https://news.ycombinator.com/item?id=6864088 https://news.ycombinator.com/item?id=6864088 : > So according to thes

chockablock investigated that here on HN, at https://news.ycombinator.com/item?id=6864088 https://news.ycombinator.com/item?id=6864088 : > So according to these rough calculations the great smog of 1952 probably had a PM2.5 of about 700 ug/m^3, quite similar to the current Shanghai smog, and lower than levels regularly reported in other Chinese cities. The current PM2.5 for Beijing, at http://aqicn.org/city/beijing/ http://aqicn.org/city/beijing/ , is 162 - "unhealthy".