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January 20, 2011

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Visibility a gauge of HK death rates

VISIBILITY in Hong Kong has deteriorated so sharply over the past 50 years because of air pollution that variations in levels can be used to predict mortality rates, health experts said yesterday.

On an average day, visibility is now 12.6 kilometers, well below that of cities such as Paris, Berlin, Auckland or Vancouver, where visibility stands at 20-25km or beyond. Using government data, researchers at the University of Hong Kong found that the number of hazy days when visibility fell to below 8km shot up to 54 in 2007 from 6.6 in 1968.

For every 6.5km reduction in visibility, there was a corresponding 1.13 percent increase in the number of non-accidental deaths, such as from heart and respiratory causes. These additional deaths worked out at a total of 1,200 per year between 2007 and 2010, the experts told a news conference.

"Loss of visibility is a direct measure of serious harm to health. Loss of visibility kills people," said Anthony Hedley, Honorary Professor at the School of Public Health.

Professor Lam Tai-hing, the school's director, said: "The less you can see, the greater the harm. It is very important to believe in your eyes because at the moment, the government is still using outdated air quality objectives.

"Based on that, people are being told today's air quality is good or acceptable when in fact, if you follow the World Health Organization's air quality guidelines, it is very bad indeed." Poor visibility was due to the concentration of pollutants such as respirable suspended particulates and nitrogen dioxide, Hedley said.

While the amount of particulates in places such as Vancouver and Auckland measured between 10 to 12 micrograms per cubic meter of air, Hong Kong had 80, or seven times more.

"The higher the pollutant concentrations, the lower the visibility," Hedley said, adding that even short exposure to such pollutants was particularly dangerous for those suffering from underlying heart or lung illnesses.

"Air pollutants increase the stickiness of elements in the blood ... With increased stickiness, blood cells stick together, they form a clot. If you form a clot, you may obstruct a vessel and if the vessel is in the heart or the head, you get a heart attack or a stroke."




 

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