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Letter to the Editor of SCMP - Response to a letter on air pollution
Professor Richard Fielding’s letter headlined “Lack of will to fight pollution” on 19 December 2008 refers.
The Government is determined to improve our air quality. On our home front, we have been implementing comprehensive measures to control our emissions at source. We have capped the emissions of the power plants and required the use of ultra low sulphur diesel across all industrial and commercial processes. We are controlling products that contain volatile organic compounds in a manner similar to California. Our control on vehicular fuel and emission standards are on a par with the most stringent European requirements. To address the regional smog issue, we are working with the Guangdong Provincial Government to reduce the emissions of four key air pollutants in the region by 20% to 55% by 2010.
We are reviewing our Air Quality Objectives (AQOs), taking into account the latest international developments including the Air Quality Guidelines published by the World Health Organization.
Professor Fielding raised concern about the relationship between air pollutant concentrations and the air pollution index (API). Like many other overseas API systems, our API is computed by (i) converting the concentrations of various pollutants over different averaging times ranging from 1-hour to 24-hours into sub-indices by comparing the concentrations with the respective 1-hour to 24-hour AQOs; and (ii) taking the highest of the sub-indices as the API for a station at that hour. One should note that the AQO for respirable suspended particulates (RSP) is based on an averaging time of 24-hours instead of 1-hour, due to the lack of scientific evidence with respect to the exposure-response relationship for RSP over a period as short as one hour. Hence the API for RSP is computed based on moving 24-hour average concentrations instead of 1-hour concentrations.
The API is derived from the actual pollutant concentrations and therefore bears direct relationship with the state of air quality. On 15 December 2008, the day mentioned by Professor Fielding, the API for the general stations were on the upper side of the high band, and the roadside API were up to 104 at the Central roadside station in the afternoon. Both readings duly indicated that the pollution level on that day was considered high or very high.
To make the API more useful to the public, we have engaged a team of leading academics from local universities to review our API system and draw up their recommendations for improvement. The review will complete within 2009.
Dave Ho
Principal Environmental Protection Officer
Environmental Protection Department
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