Every time I am asked by someone who has been offered a job or a posting to China about taking it, I would advise them to not to go. Its not just the air pollution, the food hygiene its what starts unravelling in 5 star hotels and swanky restaurants etc. When China bought IBM PC business, they hired an Expat to run the show. He refused to move to China and they agreed that his home will be Singapore and he would commute weekly. And he did for years.
Its not just China. Advised a guy not to take a posting to Reuters Mumbai and he did and regretted it. There are better opportunities in 1st World countries and if you are good you can match the locals in places like London and the US.