Silly article. Sulfur dioxide is one of the most common industrial pollutants.
Except the factories there are closed, yes?
Articles discussing the factory closures:
https://www.google.com/amp/s/www.businessinsider.com/wuhan-coronavirus-which-companies-shut-down-operations-move-employees-2020-1%3famp
https://www.just-auto.com/news/plant-closures-in-china-extended-as-coronavirus-crisis-worsens_id193547.aspx