Air pollution experts have again called for a new alert system to warn the public about health risks created by extreme pollution like the grey pall over Hong Kong yesterday.
They issued the appeal as the city choked for a second consecutive day in what green activists called 'life-threatening' levels of air pollution.
Roadside readings in Central hovered at or above 190 for 20 hours beginning on Wednesday. They peaked yesterday at 7am with a reading of 212 - the highest ever recorded in Hong Kong with the exception of a sandstorm in 2010.
Roadside levels in Causeway Bay reached a historic peak of 200. By 8pm last night, the roadside readings were all still above 160.
The pollution, dominated by excessive levels of nitrogen dioxide, coincides with a heat wave that has driven the mercury to 37 degrees Celsius in Happy Valley, among other locations.
Environment officials blamed the pollution on a mass of still, subsiding air caused by Typhoon Saola near Taiwan.
Professor Wong Tze-wai, from Chinese University's School of Public Health, said he expected a surge in the number of people seeking treatment for respiratory diseases in the next few days. 'Even wearing a mask wouldn't have made any difference in the past two days,' he said.
Alfred Tam Yat-cheung, a paediatrician in Central, confirmed Wong's worries, saying he treated more patients than usual yesterday. 'Some kids whom I had thought were recovering had their allergies and asthma back again or getting worse.'
The Hedley Environmental Index - a real-time tracker of Hong Kong's air pollution - said yesterday's extreme levels would lead to more than 17 premature deaths and over 800 hospital admissions. Despite the threat to public health, Wong said the government's alert system failed to link pollution levels with health risks.
To clarify that link, a group of experts from local universities, including Wong, developed a new alert system several years ago that takes health risks into account. The system grew out of a study commissioned by the Environmental Protection Department.
'We did our studies and handed it to the Environmental Protection Department in 2009,' Wong said. 'But we have no idea what is blocking it from being introduced.'
He said the proposed new system is based on a cocktail of indicators, including concentrations of particular pollutants and the health consequences of exposure.
Erica Chan, from the Clean Air Network, said environment officials were slack in warning the public about the severe pollution.
'They should have sent a scientist to explain the matter, as most people don't quite understand what the air pollution index means,' Chan said. 'They could offer more suggestions specific to different groups of people, particularly street workers.'
An EPD spokesman said the department had an established mechanism to inform the public about air pollution readings. It would consider revamping the API system when it upgraded the air quality objectives. The city's air quality standards have not been revised since 1987.
The number of premature deaths that will result from yesterday's pollution, according to the Hedley Environmental Index