Air Quality Health Index to reach 'Serious' levels amid dusty monsoon

The health risk category of the Air Quality Health Index (AQHI) at some air quality monitoring stations could reach the "Serious" level today, according to the Environmental Protection Department's forecast.

The Department noted that under the influence of a dusty air stream associated with the northeast monsoon, the background levels of pollutants including suspended particulates have been recorded higher than normal since 10pm on Saturday night (April 12).

With the monsoon moderating gradually, winds in Hong Kong are expected to weaken and unfavorable to pollutant dispersion in the city, leading to an increase in pollution levels. 

According to the AQHI monitoring page on the Environmental Protection Department's website, the concentration of respirable suspended particulates (PM10) in several areas surged last night, ranging from more than 10 times to 30 or 40 times. 

Among them, the record of general monitoring stations in Central/Western increased from 7.5 μg/m3 at 9pm last night to 275.7 μg/m3 at midnight, an over 35 times rise within 3 hours.

The Sham Shui Po general monitoring station also recorded an increase of PM10 from 15.2 μg/m3 at 9pm last night to 212 μg/m3 during midnight.

The pollutant level is anticipated to remain relatively high in the following one or two days. 

With a health risk category in the "Very High" range or above, children, the elderly and persons with existing heart or respiratory illnesses are advised to reduce physical exertion and outdoor activities to a minimum or avoid such activities. The general public is advised to reduce, or reduce to a minimum, outdoor physical exertion, and to reduce time outdoors, especially in areas with heavy traffic. 

EPD noted that the concentration of fine suspended particulates (PM2.5), which could affect human health directly, recorded a relatively low increase.

It added that Hong Kong has been affected by dusty air streams in the past, with the duration of the impact ranging from a few hours to a few days and the impact is expected to be similar to the accumulation of air pollutants under normal calm winds.

(Kelvin Wan)