This would seem to be highly dependent on what is in the pollution. For example, the concern with burning coal is it often contains mercury and releases it into the air when burned.
While considered harmless, it probably isn't for people who have already accumulated too much mercury.
Your second article mentions breathable particles as an issue. These seem to be a larger issue with lung diseases and lung cancer than PD. These particles are what we call smoke and have the same issue with smoking. I'm wondering if their unknown factor is they are not considering chemicals known to cause PD within some pollution.
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