I think you have a point. If there were no people on Earth, what would the PM 2.5 look like? If it would still be too high, then it seems this measure while,

I think you have a point. If there were no people on Earth, what would the PM 2.5 look like? If it would still be too high, then it seems this measure while, baseline to know, wouldn't be practically useful. We'd have to then control naturally occurring PM2.5 in the environment. That's not to say the obvious is not true, that Regions of China and India suffer from too much PM2.5 due to human activity and should be addressed. However, a chicken little situation is not helpful as people will tune out.