Air pollution soared to its highest level in more than a year yesterday, with diesel vehicles singled out as as the worst contributors.
The highest reading of 140 on the air pollution index was recorded in Causeway Bay at 8am. By 2pm, pollution in the area had dropped marginally to 139.
In Mongkok, the reading peaked at 120 at 2pm, while roadside pollution in Central dropped from a high of 114 at 3am to about 100 by early afternoon.
When the air pollution index hits 100, a health warning is issued to those with respiratory or heart disease.
Nitrogen dioxide, a component of vehicle exhausts, was identified as the major contributor to yesterday's pollution, but Sarah Liao Sau-tung, the Secretary for Environment, Transport and Works, said the poor air quality was only 'episodic' and brought about by a lack of wind.
In an effort to clear the air, the government recently introduced an ultra-low sulphur diesel and partly implemented a tighter vehicle emissions standard, known as Euro III.
About 80 per cent (or 24,000) of pre-Euro III light diesel vehicles have since been fitted with a device to reduce particle emissions, and more than 90 per cent of Hong Kong's taxis now run on liquefied petroleum gas.
Dr Liao said yesterday her bureau had also asked bus companies to deploy more low-emission buses in busy streets in Causeway Bay, Central and Mongkok, where long bus queues are common.
'We will be working on capping the emission levels of bus fleets entering the busy areas. If they do not meet the requirement, they might not be allowed to enter the areas,' she said.
But Hung Wing-tat, associate professor at the Polytechnic University's department of civil and structural engineering, said the fact that the current pollution was coming from diesel vehicles was a clear indication the government needed to maintain pressure to improve air quality.
'The problem will continue unless we go [wholly] to Euro III, or even higher standards [of emission controls]. Retro-fitting vehicles will not solve the problem because it has little effect on nitrogen oxide,' he warned.
Clear the Air chairman Lincoln Chan said: 'The government has done a lot of things, but not enough. When you compare 2001 and 2002 figures, air quality should be improving.'
Yesterday's reading at Causeway Bay was the highest roadside reading since January 7 last year, when it rose to 140 after a high of 153 at the same station on January 1 last year.
The highest readings at general stations yesterday were 105 at Kwai Chung and 104 at Kwun Tong. The record high for the air pollution index is 185, reached at the airport town of Tung Chung on September 9 last year.
Anthony Hedley, chair of community medicine at the University of Hong Kong, said the high pollution was 'totally unacceptable'.
'Pollutants, even at very much lower levels, cause damage to people's health and result in early death,' he said.
Friends of the Earth campaign director Daphne Mah Ngar-yin called on the government to do more. 'The government has underestimated the wide-scale application of renewable energy in Hong Kong,' she said.