A cloud over air quality index

PUBLISHED : Thursday, 30 October, 1997, 12:00am
UPDATED : Thursday, 30 October, 1997, 12:00am

I would appreciate an explanation from the Environmental Protection Department (EPD) regarding its air quality index (AQI).

For nearly every day of the past several months there has been very low visibility in Hong Kong. On many days one can see no more than a few kilometres, when under clear conditions an unobstructed view from a moderate elevation should be 20 to 30 kilometres.

Yet, each evening the TV weather report tells us that air quality is 'good to moderate'. As I write this, the view from my office window is so obscured by haze that I cannot see the four kilometres across the western harbour! Yet, the evening's report said air quality would be 'moderate'.

The EPD reports in its annual reviews that average annual air quality for Hong Kong is unhealthy in most urban areas with respect to suspended particulates even though the air quality is reported to be 'good to moderate' every day.

Experts surely can explain the apparent discrepancy, but is not the purpose of the AQI to inform the general public? Unfortunately, in its present form the AQI report on the news misleads viewers about the overall quality of the air we breathe.

Air quality in much of Southeast Asia near Indonesia has been very unhealthy for much of the past weeks. Yet, on a year basis how much worse is their air than Hong Kong's? Once the fires are out, much of their haze will go away, while ours seems now to be virtually a permanent fact of life.

I ask the EPD if it would be useful to also produce a daily air quality rating which is a running average of how each day's pollution would - if continued for a year - compare against annual average standards.

I would appreciate comments from the EPD regarding the present AQI rating system and whether the types of suggestions made above are feasible.

WILLIAM BARRON Centre of Urban Planning and Environmental Management University of Hong Kong