Combustion of industrial waste gas, automobile exhaust gas and combustible materials, such as combustion of fossil fuels (coal, gasoline and diesel oil), combustion of biomass (straw and firewood) and garbage incineration; Dust, such as road dust, construction dust, industrial dust, wind dust, etc. ; Volcanic ash, forest fires, floating sea salt, pollen, fungal spores and bacteria all affect air quality and endanger human health.
So the answer is: √.