Residents at risk as ‘1 in 5 subdivided Hong Kong flats has hazardous air pollutants exceeding safe limits’

One in five subdivided flats in the city has excessive levels of tiny, hazardous air pollutants, putting residents' health at risk, a study has found.

Two NGOs - Clean Air Network and Concerning CSSA and Low Income Alliance - recently visited 44 subdivided flats in six districts to measure the level of PM2.5, particulate matter with a diameter of 2.5 micrometres that can penetrate deep into the lungs and lead to heart and respiratory ailments.

They found that the PM2.5 levels of nine flats exceeded the World Health Organisation guideline of 25 micrograms per cubic metre, with the worst reading being 124 - almost five times the WHO standard.

"Many of the subdivided flats are located in areas with busy traffic," said Loong Tsz-wai, community relations manager of Clean Air Network. "Some of the flats also do not have any windows, making it very hard for the PM2.5 pollutants to disperse."

He also said the "street canyon effect" contributed to poor air quality, created when closely built high-rises, with heavy traffic in between, block ventilation and trap air pollutants.

Of the nine flats recording PM2.5 levels that exceeded WHO standards, three were in Sham Shui Po, one in Mong Kok, four in Kwai Tsing, and one in To Kwa Wan. The most serious reading of 124 was recorded in Kwai Tsing.

About half of the respondents described the air pollution problem in their flats as "serious" or "very serious". About 10 per cent said they had problems with their throats and tracheas.

Szeto Keung, 75, has lived in a subdivided flat in Sham Shui Po for several years. He said he often has problems with his throat because of the poor air quality.

"I go to the hospital once or twice every month," he said.

Loong said the government should offer electricity subsidies during the summer to residents of subdivided flats. He added that air conditioner use can improve ventilation and reduce health risks associated with PM2.5.