|Air Quality, PM10 (soot), in Wohan, China 2006-to-2008. Source, Table 5|
PM10 is soot/smoke and is a decent indicator of local industrial activity because it is mostly a byproduct of burning coal. That is why it goes up in the winter, increased use of coal for space heating. Particulates drop out so it is more LOCAL than some other measures.
PM10 and its bratty sister PM2.5 are also important because they are damaging to lungs. Historically high PM numbers may predispose lungs to pneumonia from other causes...like Covid-19.
|PM10 in Wohan since Jan 20. Starting Feb 5 PM10 has been around 30 micrograms per m^3, or 25% of expected. 30 micrograms per m^3 is about what is seen in Los Angeles. The low occurred on Feb 14 at 16.9 micrograms. Source|
|Same data for Beijing, China as the chart immediately above. Odd periodicity.|