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February 2nd, 2009:

Pollution Study Points To Dangers Of ‘Canyon Effect’

Cheung Chi-fai, SCMP – Updated on Feb 02, 2009

The “canyon effect” is to blame for the much higher level of ultrafine air pollutants at bus stops on “walled streets” in Central compared with those in more ventilated areas, a study has shown.

In one comparison, the number of pollutants nearly doubled. The canyon effect refers to the impact – such as poor ventilation and trapped heat – from the creation of canyon-like streets between walls of closely spaced tall buildings.

The study measured the number of ultrafine particles in every cubic centimetre of air, rather than the government’s pollution-monitoring method that tracks the weight of larger particles in every cubic metre of

Ultrafine particles can be as tiny as 20 nanometres in diameter – 2,500 times smaller than the diameter of a human hair.

Although there are no international standards on acceptable levels of the number of ultrafine particles in the air, overseas studies have found they can penetrate directly into blood vessels and lung tissue, causing
harm. Many scientists believe they may be the most harmful form of air pollution.

The Hong Kong study was conducted last year by students at the University of Science and Technology. They found the air at bus stops at sites between walls of buildings on streets with heavy traffic had more ultrafine pollutants than that at bus stops in open spaces, seaward streets and indoors.

The number of particles at the two eastbound bus stops outside Wing Lung Bank and the old Hang Seng building at Des Voeux Road Central were on average 90 per cent and 75 per cent higher than at the bus stop outside Statue Square in Central.

Measurements were taken during evening peak hours on six days between September and December.

Between 48,000 and 137,000 particles were recorded at the Wing Lung Bank bus stop, between 63,000 and 100,000 at the old Hang Seng Bank building bus stop, and a range of 22,000 to 82,000 at the Statue Square bus stop. For comparison, a benchmark reading of 20,000 was recorded at the researchers’ Sai Kung campus on a clear and fine summer day.

Des Voeux Road Central is surrounded by buildings on both sides while the Statue Square stop has more open space in its vicinity, although more buses pass by the square.

“The findings strongly suggest the presence of the canyon effect in Central,” said Lau Ngai-ting, the project’s supervisor. “The number of particles one inhales in the streets would be astronomical.”

He said that while the readings might have varied with changing weather conditions and ambient pollution levels, he believed poor ventilation contributed to higher pollution levels on the streets. Heavy traffic, such
as buses running on large diesel engines, was the key source of ultrafine particles, he said.

Researchers also measured particle levels along three different walking routes between Des Voeux Road Central and Statue Square.

On all three routes, the reading showed high levels of pollutants – hitting a high of 180,000 at one point on the road – but fell below 10,000 in elevated walkways, mall corridors and underground rail stations, where
ventilation was better.

Adrien Chen Kam-cheuk, a chemical and environmental engineering student who initiated the study, said: “Going above ground or underground seems to be a more desirable way for commuters to avoid street-level pollution.”

Mr Lau said regulating traffic through such means as electronic road pricing or low-emission zones might help reduce the pollution level.

Demand To Step Up Monitoring Of Air Quality

Cheung Chi-fai, SCMP – Updated on Feb 02, 2009

Hong Kong should increase the number of air-quality monitoring stations, particularly at the roadside, and incorporate a measurement of very fine particles to give the public a better picture of the health risk it faces, a critic says.

The issue has been raised as the government plans to consult the public on the air-quality objectives review early this year amid pressure for it to adopt the World Health Organisation’s highest standards.

But the Environmental Protection Department said there was no need to enlarge the monitoring network, although it was willing to consider expanding its fine-particles measurements and publish them online.

The city has 14 air-quality monitoring stations – 11 measuring background readings and three roadside readings of five pollutants.

The stations measuring background readings reflect the regional pollution, and the roadside ones – in Causeway Bay, Mong Kok and Central – gauge pollution posing a direct threat to people on the streets.

Only four general and one roadside station measure the level of fine particles – known as PM-2.5 – which overseas research has found to pose a greater health threat.

Last year, the annual reading of fine particles at roadside level in Central reached 41 micrograms per cubic metre of air, four times the WHO standard.

“It is worth studying the issue, given our unique city environment does not favour dispersion of pollutants,” said Alexis Lau Kai-hon, the manager of the Environmental Central Facility at the University of Science and

However, Choy So-yuk, a North Point-based district councillor and a member of the Council for Sustainable Development, said it was far more important for the government to improve roadside air quality than to build
more stations.

“Everybody knows the air quality in North Point is far worse than in Central, even without a monitoring station,” she said.

Ms Choy said officials should focus more on getting rid of the wall effect in the city by cutting building heights, and increasing the number of green areas in busy parts of the city.

Air Quality In Need Of Attention

Study proves air quality is still in need of attention

Updated on Feb 02, 2009 – SCMP

A clear sky and moderate air pollution index reading may seem favourable circumstances for a stroll, but they do not give the full picture. As we report today, a University of Science and Technology study has found that unnoticeable ultrafine particles not adequately measured by the Environmental Protection Department are ever-present, and in some locations, worryingly so. Small amounts are known to cause heart and breathing problems, particularly for the elderly. Higher measurement standards are clearly needed, as is greater effort to reducing the level of roadside pollutants. This is not to say that the government is failing us when it comes to cleaning up the environment. Improved visibility is a fact of life in some parts of the city. The concentration of several major roadside pollutants has fallen 20 per cent over the past decade. Eastern district has not had a reading of more than 100 on the air pollution index since 2005, and with the two other cleanest districts – Tai Po and Sha Tin – has recorded consistently improved figures.

Among the reasons are tighter vehicle emission standards, the introduction of ultra-low-sulfur diesel, the conversion of taxis and minibuses to LPG, and tougher control measures adopted by Guangdong province. All is not sweet air and light, of course – there is a lack of improvement in many other parts of the city. That the situation could be considerably worse than we think at roadsides takes the matter to quite another level.

Decades of air pollution studies have shown that the worse the air quality, the greater the risk of hospital stays and death from heart and lung disease. The fine particles in vehicle emissions have been determined to be more dangerous to health than gaseous pollutants. Microscopic particles – those measured by the university study but not widely taken into account by authorities – were especially troublesome because they could get into the bloodstream and more readily damage lung tissue. Particularly vulnerable were people with heart and lung problems and asthma, and the elderly.

Research at bus stops on Des Voeux Road in Central found invisible particulates were at alarming levels at points where buildings created a “canyon effect”. Levels dropped considerably in open spaces, underground passages and on elevated walkways. The readings are highly localised in nature. Nonetheless, we should be worried that waiting for a bus could be a health risk.

Our air quality standards are considerably lower than those recommended by the World Health Organisation. A government panel is finalising a study that will look into whether these should be adopted. It is clear that they should be – urgently.

More has to be done to cut roadside emissions. Hybrid and electric vehicles have to be encouraged. Urban design has to lessen the canyon effect. Doing so is in all our interests.

Clean Air Prolongs Life

Medi watch – Jerome Watson – SCMP – Updated on Feb 02, 2009

Cleaner air increased life expectancies in 51 US cities by a “remarkable” five months, on average, and by double that in what were the worst polluted areas, say researchers from Brigham Young and Harvard universities, based on an analysis of data over two decades. By 2000, Americans were living 2.72 years longer, on average, than 20 years earlier, with as much as five months of that gain due to reduced pollution, AP reports. “Such a significant increase … is remarkable,” says team leader Arden Pope.