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Hong Kong’s Air Pollution Index is shamefully misleading

South China Morning Post – 27 Jan 2012

In the executive summary of his paper Air Pollution and Public Health, written in 2009, University of Hong Kong Professor Anthony Hedley writes: “There is incontrovertible evidence that pollution levels currently experienced throughout the year in Hong Kong are causing an epidemic of health problems arising from damage to lungs, heart and blood vessels. Hong Kong’s pollution is a significant cause of premature death from cardiopulmonary disorders.

“Present levels of pollution cause injury to the immature developing lungs of children and adolescents. This damage will lead to lifelong health problems in many and a reduction in life expectancy.”

Professor Wong Tze Wai, with the Chinese University of Hong Kong, concluded an earlier paper, Health Impact of Roadside Air Pollution, by observing that: “Roadside air pollution is a cause for concern; levels of air pollutants at roadside are very high; public health is severely affected; needs urgent action to reduce roadside levels…”

Given these dire warnings by acknowledged public health experts, it is curious that roadside pollution does not excite the same sort of fears in the mind of the public as Sars and bird flu, even though it is responsible for far more deaths.

The World Health Organisation says there have been 341 deaths worldwide from bird flu since 2003 and a total of 913 deaths from Sars.

According to the Hedley Environmental Index, which measures the impact of air pollution on public health in Hong Kong, the average annual number of avoidable deaths attributable to air pollution over the past five years is 3,200. That is a total of 16,000 avoidable deaths in Hong Kong over the past five years alone. These figures are arrived at by a peer-reviewed methodology and have not been challenged by the government or the medical profession.

One of the reasons for the apparent lack of concern is that those struck down are not pronounced dead as a result of contracting a disease with a name like bird flu. It is a “silent injury”. People die from toxic attack on their respiratory and other functions.

Another reason for the apparent lack of understanding by the public of the risks posed by air pollution is the government’s Air Pollution Index. This takes the readings from the government’s air monitoring stations and reduces them to one number on a scale of 0 to 500 and divides the scale into five broad levels ranging from low to severe.

The system is explained at: The problem is that these measurements are based on Hong Kong’s woefully outdated air quality objectives set in 1987 and hugely understate the health impacts. (See how API relates to air quality objectives (AQOs) at

Try comparing the government’s API and the Hedley index ( We did this several days last week when the API index indicated low and “safe to go out”, while the Hedley index, using the same data but calibrated to the World Health Organisation Guidelines, measured “very poor”.

In other words, the API is completely misleading. Or as Professor Hedley called it on RTHK’sBackchat programme, “a complete piece of fiction”. He added: “It’s the government’s responsibility to translate this problem into health risks and to inform people what they are facing and what their children will face in future years – even if they clean up tomorrow.”

So perhaps it is time for Secretary of the Environment Edward Yau Tang-wah (Golden Bauhinia) to stop this shameful practice and either publish figures that indicate the true health impacts or to stop publishing this information, which deliberately misleads the public.

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