13rd, January, 2010
EPA Thick smog hangs over Hong Kong. Air pollution reached dangerous levels one of every eight days in 2009, according to news reports.
The air pollution in Hong Kong reached “life threatening” levels on average one in every eight days in 2009, The South China Morning Post reported in an article that was picked up widely by other news media last week.
According to the report, the “roadside air pollution index” recorded by Hong Kong’s Environmental Protection Department indicated “very high pollution” on at least 44 days in the city’s central district — up from 39 days in 2008.
Green Inc. reached out to Eva Wong, a spokeswoman with the Environmental Protection Department, to discuss the situation. Excerpts from that e-mail exchange are below.
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Q.
Has the air pollution situation in Hong Kong really become worse in 2009 compared with previous years?
A.
Concentrations of all the major pollutants except ozone in the general (ambient) air reduced in 2009 as compared with 1999. At the roadside, there are also discernible signs of air quality improvements due to the comprehensive vehicle emission control programs taken after 1999.
However, nitrogen dioxide concentration rose by 11 percent in the period.
The rise in nitrogen dioxide concentration at the roadside in 2009 could be explained by the high level of solar radiation and lower than normal rainfall, which favors the photochemical formation of ozone in the region. Hence, 2009 saw a rise in ozone concentration in the ambient air by 10 percent as compared with 2008. The higher ozone concentration is conducive to the oxidation of nitrogen monoxide emitted from vehicles to form nitrogen dioxide, resulting in a higher nitrogen dioxide concentration at the roadside.
Q.
Is it true that the air pollution in Hong Kong is already so consistently dangerous that the threshold for severe harm to human health is exceeded almost every day?
A.
The health effects of air pollution vary according to the species of the causing air pollutants and their concentrations.
To alert the public to the health risk posed by air pollution, particularly in the short term, most countries use an air pollution index (A.P.I.), the compilation of which does not have a universal methodology.
In Hong Kong, the A.P.I. system was developed originally based on the former U.S. Pollutants Standards Index system. It is in general comparable with those adopted in other Asian cities, such as Singapore and Taipei. Like the A.P.I. systems in other cities, we provide advice to those more susceptible to air pollution, such as those with heart and respiratory illnesses, to take precautionary measures when the A.P.I. reaches the very high band — i.e., an A.P.I. exceeding the 100 mark.
Apart from emissions, weather conditions affect daily air pollution levels. We usually have good air quality in summer because the summer monsoon brings a cleaner background airstream from the ocean and the air-mixing level is higher favoring the dispersion of pollutants. Our air pollution is higher on days with unfavorable weather conditions that hinder dispersion, or favor photochemical smog formation and when we are under the influence of the continental airstream. Such conditions more often occur in autumn and winter.
On the whole in 2009, the A.P.I. level breached the 100 mark 7 percent to 13 percent of the time at each of our three roadside air-quality monitoring stations.
Q.
We understand that Hong Kong’s air-pollution index allows for levels of emissions many times higher than those recommended under the World Health Organization’s Air Quality Guidelines. Can you comment?
A.
Our A.P.I. system makes reference to Hong Kong’s current Air Quality Objectives (A.Q.O.’s). In response to the release of a new air-quality guideline by the WHO, we are in the process of updating our A.Q.O.’s.
We are considering the views gathered from a public consultation on a set of proposed new A.Q.O.’s, which are largely comparable with those of the European Union, and a host of air-quality improvement measures for achieving the proposed new A.Q.O.’s with an aim to deciding how best to take forward the updating.
Meanwhile, we have also commissioned the health experts of the local universities to review our A.P.I. system for better communication of the air-pollution levels and their respective health effects to the public.