New PM2.5 Pollution Study Showing Major Roadside Air Pollution Hotspots Along the Tramway

HONG KONG, Thursday, 30 April 2015 – Independent public policy think-tank Civic Exchange co-launched a new report today with Institute for the Environment of HKUST, entitled “PM2.5 Pollution along the Tramway”. This report aims to provide some insights into effective policy options for reducing people’s exposure to toxic air pollutants and protecting public health in Hong Kong’s dense urban setting.


In early 2013, an HKUST research team together with Civic Exchange engaged Hong Kong Tramways to explore a potential research project that would measure urban air quality on the northern shore of Hong Kong Island along the tramway. The idea was to install an air quality monitoring unit on a tramcar for year-round, real-time collection of air quality samples, with the objectives of measuring PM2.5 concentrations along the tramway, and investigating the correlation between street-level air quality and urban morphology.

An air quality monitoring unit that mainly composed of an aerosol monitor and a Global Positioning System (GPS) locator was installed on one of the tramcars. PM2.5 concentrations and GPS location information were collected every second, which were then fed into a database system managed by the HKUST team for processing and analysis. Actual PM2.5 measurement began in August 2013, with the tramcar operating under normal condition from 6:00 in the morning until midnight, except on the planned maintenance days.

To examine the correlation between PM2.5 concentrations and urban morphology, the HKUST study also used the plan area index and frontal area index to characterise urban and building morphology along the tramway and their impacts on urban wind ventilation and air pollution dispersion.

Key findings:

  • PM2.5 pollution hotspots: Annual average PM2.5 concentrations were highest along Des Voeux Road Central (close to 55 µg/m3), followed by Hennessy Road/Yee Wo Street in Causeway Bay. High PM2.5 concentrations were also found in Des Voeux Road West in Western District and King’s Road in North Point. As a reference, Hong Kong’s annual average air quality objective (AQO) for PM2.5 is 35 µg/m3, whereas WHO’s recommended standard is 10 µg/m3.
  • PM2.5 daily average concentrations non-compliant with HK air quality objectives (75 µg/m3): PM2.5 daily average concentrations in areas like Central, Causeway Bay and part of Western District exceeded Hong Kong’s AQO in 15 to 20 days each year.
  • PM2.5 daily average concentrations non-compliant with WHO’s air quality guideline (25µg/m3): PM2.5 daily average concentrations exceeded WHO AQG in Central and Causeway Bay (about 280 days), Western District, Admiralty and most of Wan Chai (over 200 days), North Point (over 150 days), and Eastern District (over 80 days).
  • PM2.5 concentrations and urban morphology: there is a moderately positive correlation between urban morphology and PM2.5 concentrations in Central and Wan Chai.

Policy recommendations:

So far, Government actions that address roadside air pollution are too focused on reducing emissions from road vehicles. This is an important part of the solution, but not the only solution.

We argued that the Government should make it a policy priority to improve roadside air quality in major urban street canyons, such as the main traffic corridors along the tramway, to a level where people’s health can be protected. Specifically,

  1. The Government should make reference to health-based guideline, such as the WHO AQG, and set air quality targets in concentration (in µg/m3) for major roadside air pollution hotspots;
  2. In order to achieve the air quality targets, the Government should take away road traffic from urban street canyons whenever opportunities arise;
  3. Pedestrianisation scheme and low emission zone should not be discussed exclusively for Central, Causeway Bay and Mong Kok. Other locations where roadside air quality is equally bad, such as Des Voeux Road West, Hennessy Road and King’s Road, should also be considered;
  4. The Government should devise a long-term strategy to improve wind ventilation and air dispersion in urban street canyons with every new development and urban re-development opportunities; and
  5. The Government should explore the possibility of deploying new monitoring techniques, mobile and stationary, with university partners and other research organisations in order to expand both the temporal and spatial coverage of air quality monitoring.

“Roadside air quality is something we much improve in Hong Kong, as people’s health will be badly affected. We need more data to understand the situation and to find the most effective solutions, but right now, street-level air quality data are only collected at EPD’s roadside monitoring stations in Central, Causeway Bay and Mong Kok,” says Jimmy Fung, Head and Professor of HKUST’s Division of Environment. “With due attention to system calibration and data quality control, this tramway monitoring platform could well become a complementary system to the government’s monitoring station network and fill important data gaps”, Fung added.

“At present, most government efforts focused on tailpipe solutions. Very little has been considered to improve air pollutant dispersion in urban street canyons and to reduce people’s exposure to roadside emissions through planning and transport management measures,” claimed Simon Ng, Chief Research Officer of Civic Exchange. “Our Government must make it a policy priority to improve roadside air quality in major urban street canyons if we want to see any real progress,” Ng asserted.

Download report (PM2.5 Pollution along the Tramway):

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