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Air pollution danger days rise in 2008

API shows street-level air worsens

Daniel Sin – SCMP – Updated on Jan 02, 2009

Despite clearer skies and government efforts to switch vehicles to cleaner fuel, the air was dirtier than ever across much of the city last year, according to air pollution index data.

The number of hours in which street-level pollution exceeded danger levels at three of the most crowded areas rose by 14 per cent – and by more than 40 per cent in one area.

Meanwhile, in the western parts of the city, which have the worst air quality, the number of hours in which the ambient air pollution exceeded danger levels also rose, although cleaner areas of the city saw an improvement in air quality.

The figures prompted a warning from a university expert of the long-term health effects on residents.

But the government insisted air quality was in fact improving, saying the API as now calculated did not give the full picture – a response that raised questions from an environmental group about why it is still being used.

The number of hours last year when roadside pollution, measured by monitoring stations in Central, Causeway Bay and Mong Kok, exceeded an API of 100 totalled 2,007, up 14 per cent from 1,760 hours in 2007, and a six-year high.

An API of over 100 indicates the pollutants in the air pose immediate health risks, especially to people with respiratory or heart illnesses.

The API figures, published by the Environmental Protection Department, show that roadside air quality was the poorest in Central, where 1,013 hours of API readings over 100 were recorded, up 34.2 per cent from 2007. This was followed by Mong Kok, which had slightly fewer than 600 hours above the threshold, a drop of 18.1 per cent. In Causeway Bay, there were 402 hours of poor air quality, up 42.6 per cent from 2007.

An Environmental Protection Department spokeswoman said that as the API was based on just one of a list of pollutants that recorded the highest concentration on a given day, the readings did not represent the trend of air pollution concentrations.

“A more scientific, robust and commonly adopted approach by professionals to assess long-term air quality trends is to examine the annual trends of air pollutant concentrations,” she said.

Friends of the Earth environmental affairs officer Angus Wong Chung-yin found the explanation confusing.

“[It] shows the API is not sufficient to give the public an accurate picture of the air pollution if people are not able to draw a conclusion from the trend figures,” he said. “In this case, the government should review the approach and develop better indicators to help people understand the changing situation in air quality.”

On the department’s claim that roadside concentrations of some pollutants had fallen, Mr Wong admitted there had been an improvement, but it appeared to have levelled off since 2004.

Professor Wong Tze-wai, of Chinese University’s department of community and family medicine, said the health impact could be long-lasting. “Our research shows that an increase in 10 micrograms of a pollutant in every cubic metre of air will increase the rate of death, hospitalisation or treatment in a clinic by 1 to 1.5 per cent, depending on the type of the pollutant,” he said.

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