Hong Kong authorities advised members of the public to take precautions as air pollution levels in some areas of the city could reach the "serious" level later on Sunday.

According to the Environmental Protection Department (EPD), the health risk category of Air Quality Health Index (AQHI) reached the "very high" level at air quality monitoring stations in Tuen Mun, Yuen Long, North, Tai Po, Kwun Tong, Tseung Kwan O, Central/Western, and Eastern districts on Sunday morning.

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Under the influence of a dusty air stream associated with the northeast monsoon, the level of suspended particulates in background pollutants has been recorded higher than normal since 10 pm on Saturday, the EPD said.

With the monsoon moderating gradually, winds in Hong Kong are expected to weaken and unfavorable to pollutant dispersion, leading to increase in pollution levels, the department said, adding that the pollutant level will remain relatively high in the next day or two.

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With a health risk category in the "very high" range, children, the elderly, and persons with existing heart or respiratory illnesses were advised to reduce physical exertion and outdoor activities to a minimum or avoid such activities.

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"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," the EPD said.

The Education Bureau also urged all schools to visit the EDB website for appropriate measures to safeguard students' health and take note of changes in the index.