Wan Chai's Hennessy Road has the worst roadside air pollution in the city, according to findings of a new study by the Civic Exchange.

The study, released Tuesday, gauged roadside air pollution in the city's 18 districts. The study concluded that curbside pollution was heavily influenced by lack of open space and traffic stoppages rather than by traffic density.

For example, average nitrogen dioxide levels recorded along the Kwun Tong Bypass where some 96,700 vehicles ply its surface everyday were at 180 micrograms per cubic meter (mg/m3), compared to 380 mg/m3 on Nathan Road which sees less than half the traffic volume at 41,400 vehicles per day.

Identifying roads that were heavily developed on both sides as especially susceptible to the accumulation of pollution, the think tank's Chief Executive Officer Christine Loh said readings for Hennessy Road were off the charts, logging in at 480 mg/m3 even though only 24,000 vehicles per day were observed.

In contrast, the van found average readings were at 80 mg/m3 in Stanley.

A plethora of pedestrians, bus stops, traffic lights and poor urban ventilation taken together made Hennessy Road the worst for roadside air pollution exposure, she said.

Using a van outfitted with sensors on a three-meter-tall probe, a team from the Hong Kong University of Science and Technology's Institute for the Environment led by director Chan Chak-keung found levels of nitrogen dioxide in congested arteries were two to three times higher than the World Health Organization's recommended level of 200 mg/m3 and still in excess of the city's outdated air quality target of 300 mg/m3.

Loh said their readings were on the conservative side. She said pedestrians likely were inhaling more pollutants than government estimates and even more than the findings revealed by the current survey.

"Because (the probe) is a little bit higher, that's where the air has already mixed, but [the air quality] where we're standing in terms of where our mouths and noses are is essentially worse," she said.

The other most seriously polluted roads identified in the study were Ma Tau Wai Road, Kwun Tong Road, Des Voeux Road Central, Gloucester Road and King's Road.

Container Port Road South was also identified as a black spot for sulfur dioxide with 70 mg/m3 recorded and attributed directly to marine emissions from the nearby Kwai Chung Container Port.

Currently, the government has only three roadside air pollution readers, stationed in Central, Causeway Bay and Mong Kok.

Loh suggested the administration complement their data collection with mobile systems to create a more accurate assessment of the city's roadside ills while identifying areas largely left out of air improvement measures.

Franchised buses make up roughly 40 percent of traffic volume in busy urban arteries and the government is proposing the setting up of low emission zones that would prevent all but the latest low-emission buses from entering.

Community Outreach Officer of the Clean Air Network Erica Chan suggested the government extend the proposed zones. So far the zones cover only busy pedestrian corridors, including areas with high concentrations of medical facilities and schools. The principal aim is to protect the young, the elderly and the chronically ill.

The readings were collected by a mobile real-time air-monitoring platform dubbed "MAP" and financed by the Hong Kong Jockey Club Charities Trust.

Built by the Hong Kong University of Science and Technology, it collected roadside air quality data over 30,000 kilometers in Macao and Hong Kong.

China Daily

(HK Edition 06/23/2010 page1)