Average hours of unhealthy air in Hong Kong up on last year
Average Hongkonger has already breathed polluted air for more hours this year than they did in all of last year, figures show
Hongkongers endured an average of 2,727 hours of unhealthy air this year, surpassing last year's figure with a week to spare.
The Post examined hourly air pollution index (API) data from the Environmental Protection Department's 11 general air quality monitoring stations and three roadside stations.
From January 1 to December 21, the average number of hours of high, very high or severe air pollution recorded by each general monitoring station rose 7.6 per cent from last year's 2,534.
The API measures concentrations of major air pollutants such as carbon monoxide and respirable suspended particulates in a range of 0 to 500. Readings above 51 are "high" - acceptable in the short term but beyond long-term health standards. "Very high" is above 100, indicating air that is unhealthy in both the short term and the long term. "Severe" readings are above 200.
The worst performing areas with stations this year were Central & Western, Kwun Tong, Sham Shui Po and Yuen Long, each recording more than 3,000 hours of high to severe pollution. Only the stations at Tai Po and Tung Chung saw improvements.
While the total hours of unhealthy air rose slightly, hours of high to severe pollution recorded at the department's three roadside monitoring stations fell from an average of 7,949 hours last year to 7,526 hours this year, arresting a steady 10-year trend.
Roadside pollution in Central increased slightly this year, while the level in Causeway Bay remained steady. Mong Kok was the only roadside station that recorded an improvement, with the average number of hours of high to severe air pollution dropping 11 per cent from last year.
Professor Alexis Lau Kai-hon, of the University of Science and Technology's environment division, said he was not surprised by the findings. "Last year's general air pollution figures were exceptionally low, so this year's higher figure is relative," Lau said.
"But there's no denying much of this year's increase was related to the mainland."
Mainland air quality deteriorated significantly this year. This month alone, readings of PM2.5 - tiny particles which are particularly hazardous to health - were off the charts in at least 25 cities.
Lau warned that although data from general stations could suggest air quality had improved a tiny amount in the last decade, pollutant levels were still consistently higher than what the World Health Organisation deems as safe.
Melonie Chau Yuet-cheung, senior environmental officer with Friends of the Earth, said this year's decrease in high roadside air pollution hours was in no way an indication of improvement in the overall air quality.
"The lower [high to severe] readings at roadside stations could mean emissions from areas like shipping contributed to general air pollution more significantly than cars this year."
Ocean-going vessels were the largest source of emissions of respirable suspended particulates and sulphur dioxide in 2011, according to the department. New legislation requiring such vessels to switch to low-sulphur fuels before berthing in Hong Kong is not expected to take effect until 2015.
Olaf Merk, a ports administrator for the Organisation for Economic Co-operation and Development, said aligned regional emission controls would be more "logical" than Hong Kong acting in isolation.
The 18-year-old API will be replaced this month by an air quality health index (AQHI), which analyses three-hour average concentrations of four major pollutants using a five-level health risk scale, with 1 indicating "low" health risk and above 10 deemed "serious".
The department says the stricter standards will mean more days will show AQHI readings at high to serious levels.