Hong Kong's roadside pollution levels were the worst ever last year, according to the Environmental Protection Department.
Readings at the three roadside monitoring stations in Central, Causeway Bay and Mong Kok showed that pollution levels were above the 100 mark more than 20 per cent of the time. This was 10 times worse than in 2005, when very high readings were recorded only 2 per cent of the time.
Exposure to bad air pollution can cause or aggravate respiratory problems or heart disease.
Environmentalists renewed their calls for the immediate introduction of new air quality objectives, claiming that the government had deliberately delayed their introduction to ease the way for major infrastructure projects.
The department blamed the figures on unfavourable weather conditions, worsening background pollution and the ageing vehicles on our streets.
It said a number of measures were in the pipeline to improve air quality, while the new air quality objectives would be tabled to the legislature as soon as possible.
At the roadside stations, hourly readings are taken throughout the year on major pollutants such as respirable suspended particles and nitrogen oxides. A reading over 100 means at least one pollutant fails the air quality objectives.
The station in Central showed the worst figures, with excessive readings a quarter of the time, followed by Causeway Bay at 21 per cent, and Mong Kok at 17 per cent.
The total number of hours with excessive readings was even more than in 2010, when a sandstorm hit the city in March and pushed up the figures. In that year the three stations had an average excess API reading of 17 per cent.
Pollution readings at 11 general stations, which reflect more background and regional pollution, however, remained steady and similar to previous years.
The department said increased nitrogen dioxide levels at the roadside and poor weather conditions were behind the worsening air pollution readings. While other pollutants such as sulphur dioxide have fallen, the department said the nitrogen dioxide level by the roadside has reached the highest since 1999, at 123 micrograms per cubic metre of air.
It said the increase was related to the formation of photochemical smog, which was more active last year because there was 16 per cent more sunshine. The lack of rainfall, down by almost 40 per cent on 2010, was another unfavourable factor as it lessened the removal of pollutants from the air.
To combat the nitrogen dioxide pollution, a department spokeswoman said, catalytic reduction devices were being tested on older buses, while remote sensing technology would be used to strengthen the control of petrol and LPG vehicles.
James Middleton of Clear the Air said people did not need reminders from the department to tell them that air quality was getting worse, and officials were obviously turning a blind eye even at the health risk to themselves and their children.
'The government servants working for the EPD have children too - they share the filth in our air. The deliberate prevarication obviously comes from the very top,' Middleton said. 'This is a complete disrespect and disregard of the duty of care the administration owes to the health of the people of Hong Kong.'
Middleton said he suspected the government's failure to update air quality objectives enacted 24 years ago was deliberate so that infrastructure projects such as a third airport runway and waste incinerator could pass environmental impact studies.
In a separate set of monitoring results, on the concentration of fine particles, those with a diameter of less than 2.5 microns, the annual average roadside reading at both Central and Mong Kok marginally failed the proposed new air quality standard of 35 micrograms.
The department has not published the data, but the figures were obtained recently by Clear the Air. Fine particles are not a statutory air pollutant at present. Scientists say these particles can infiltrate the blood vessels and lungs, causing more damage than larger particles.
The department said the average concentration of fine particles at monitored locations had declined by more than a quarter over the past five years. It also said at least 60 per cent of the fine particles were generated across the border.