BEIJING (AP) — Whitney Foard Small loved China and her job as a regional director of communications for a top automaker. But after air pollution led to several stays in hospital and finally a written warning from her doctor telling her she needed to leave, Small packed up and left for Thailand.

In doing so, the Ford Motor Co. executive became another expatriate to leave China because of the country’s notoriously bad air. Other top executives whose careers would be boosted by a stint in the world’s second-largest economy and most populous consumer market are put off when considering the move.