Singapore has retained its status as the best location for expatriates in Asia while Hong Kong has fallen behind Tokyo because of bad air pollution, an annual survey released yesterday shows.

Singapore was ranked the best location for the 10th straight year, followed by Japanese cities Kobe, Yokohama and Tokyo, according to the survey by London-based ECA, which ranks cities by climate, air quality, health services, housing and personal safety, among other categories.

"Good infrastructure and healthcare facilities, low crime and health risks, and decent air quality contribute to Singapore providing the best quality of living for Asian assignees," said Lee Quane, Asian director of ECA International, which advises on expatriate packages and allowances.