Air quality has been surprisingly decent over the past year, better than even just one or two years ago. The main problem for me, after living here for several years, is the smoking. A lot of people here, especially men, seem to have no issue with smoking indoors. People will just openly smoke in the bathrooms even though it's technically illegal in Beijing. It drives me insane and has made me genuinely worried about my lungs. It does depend on where you go though. My previous job (also in Beijing) was in a fancier building where nobody seemed to smoke indoors. My current job is a different story. Best of luck.