Due the extreme air pollution in Mainland China, Hong Kong over the last 5 years has experienced increased air pollution and smog. My former student, in 2012, wrote about poor air quality in Hong Kong while she was doing her internship there with WWF. A year earlier, in 2011, I wrote about "Westerners and businessman moving their families from Hong Kong to Singapore due to the increasingly poor air quality in Hong Kong." But now it seems Singapore’s air quality is under the microscope, though in this case the poor air quality is due to fires in Indonesia. See these articles:
Singapore air pollution hits record high
Singapore’s record-breaking smog is so bad, birds are falling from the sky
Air quality at dangerous levels in Singapore and Malaysia