This is a great place to take some insurance in the way of Anti-oxidants like higher doses of Natural Vit C ( personal doses are 5000-10,000+ mg or tolerance) and Gamma Vit E (800 units+) per day! There are other supplements to protect the heart, lungs, & brain, as well as, Detox for the whole body. INcrease intake of PURE water(or Green tea )while traveling with high pollution. These are my normal daily doses!
It will make a big difference on keeping you feeing in better condition.

What are the first two weeks of October generally like re: pollution?

I understand this same period are National Holidays, and I am curious, if this means there are more or less tourists/locals traveling in PVG & PEK?