Hong Kong's athletics coach Paul Wright will leave his post in November after just over two years in the job, amid fears his son's health problems are linked to the city's high levels of pollution.
Since Wright took the job in May 2010, Hong Kong athletics has seen a significant improvement, notably qualifying for the men's 4x100 metres relay in the London Olympic Games.
But Wright, 41, said despite being just four months into his two-year contract, his five-year-old son's health had to come first.
"[He] has struggled with respiratory infections since we came here so we are prioritising getting him home and well," said UK-born Wright. "Some people have suggested the increased levels of air pollution are to blame, but we're not sure what the problem is. We just know his immune system isn't able to cope.
"Our other three children are fine … but we've had one too many visits to the hospital with Caiden coughing up blood. So we decided to do something positive about it."
Wright does not yet have another job to go to, but says there are offers on the table. It is likely he will head back to the US, where his wife is from.
Hong Kong Sports Institute chief executive Trisha Leahy credited Wright for the recent rise in athletic standards.
"Paul is moving on after a very successful two years … He has been a consistently highly-motivated, positive and professional head coach," said Leahy.
Wright and his family are not the first to have been forced to leave Hong Kong because of air pollution recently.
In May, Canadian Eric Bohm, the 68-year-old chief executive of green campaign group WWF, Hong Kong left after eight years of trying to save the city from environmental degradation.
One in four people in Hong Kong are now considering leaving due to air pollution, a study by public policy think tank Civic Exchange found last year.
Last month, Hong Kong choked under the worst smog recorded in the city. Residents were warned to stay indoors, away from the blanket of toxic haze.
At the same time, roadside air pollution set a new record with the air pollution index hitting 212 in Central, its highest level yet.