The culture is almost like a lack of any culture. You just have to adjust to new norms. The things listed below aren't rude in Chinese culture, but to a westerner they are appaling. 

People hacking up a lung and then spitting out a ball of phlegm at your shared table in a restaurant WILL happen. Often. Hell I was only there for a month and it happened countless times. 

People pushing you out of the way will happen. Constantly. 

People cutting in front of you in line will happen. Don't leave even a few cms of space.

People taking photos of you and staring at you in awe because you're a foreigner will happen.

People letting their toddlers piss and shit in the street is more accepted than spitting is in western countries. It's everywhere. 

People trying to rip you off will happen everywhere and all the time. 

On a plane, a train, or sitting on a bench in a park? Hope you don't mind the person next to you taking off their socks and picking at their feet. Everywhere is home in mainland. 

Hell, the subway in Xi'an has a "no shitting or pissing" decal next to the no smoking one. That was NECESSARY. 

Theres a reason HK and Taiwan folks don't want to be lumped in with mainlanders. It was an incredible experience, but I don't know if I could do a few years.

As for food safety, this is nothing. Look up gutter oil. Or borax. Or baby formula. Or the powders without any ingredients most restaurants are using to imitate foods. Even the fresh stuff is grown in poisoned soil.