A new study has highlighted emissions from ships as a major source of air pollution in Hong Kong.

Reports say a study from Hong Kong's University of Science and Technology has identified the container port at Kwai Chung as one of the territory's main pollution sources.

Dr Alexis Lau Kai-hon, an associate professor at the University’s Institute for the Environment, found Hong Kong's atmosphere was more polluted with sulphur dioxide (SO2) on days when the wind came from the sea than when it came from mainland China.

“It suggests the pollution source is local rather than regional,” he said.

Lau found some of the highest SO2 concentrations in and around the container port.

He warned that although power generation remained the single largest source of sulphur emissions in Hong Kong, pollution from the port could be 'five times' more dangerous because of the port’s proximity to population centres.

Lau also said the emissions data showed 'a remarkable difference' in SO2 concentrations before and after the global economic downturn.

SO2 concentrations fell by an average of 25% after the downturn began last year, coinciding with an 11% drop in the number of cargo ships visiting the port.

He said said the findings underlined the urgent need to address air pollution from marine sources.

Last year, Hong Kong’s Civil Engineering and Development Department raised concerns about the extra air pollution that could be generated if plans for a new container terminal went ahead.

It said the air quality problems could be minimised if ships visiting Hong Kong used low sulphur marine fuel .

There have been ongoing concerns about air quality in Hong Kong and Hong Kong Shipowners Association (HKSOA) has been a leading supporter of moving shipping away from residual fuels to distillates.