To be slightly more specific, Chinese authorities consider PM2.5 levels of ≤70 mcg/m³ as safe, while by EU standards that same pollution level is considered "extreme".
The WHO yearly recommended limit is 5 mcg/m³, by the way.
To give you an idea of the difference in perception. When we lived in Beijing, anything below 150 mcg/m3 was a "good day", <50 was "amazing". We didn't start taking any precautions like closing windows until it was >250. We stayed indoors when it was >400 or >500.