A man looks out onto Victoria Harbour in Hong Kong on July 22, 2022. (ISAAC LAWRENCE / AFP)

HONG KONG - Hong Kong’s environmental authorities have warned that the Air Quality Health Index (AQHI) at some of the city’s monitoring stations may reach a “serious” level later Saturday under the influence of a ridge of high pressure

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In a statement, the city’s Environment Protection Department said it has recorded higher than normal air pollution levels since Saturday morning. 

Under the influence of a ridge of high pressure, the weather in Hong Kong today is fine, dry and very hot, with light winds, which is unfavorable for pollutant dispersion and results in rising regional pollution level.

Environment Protection Department, HKSAR government

"Under the influence of a ridge of high pressure, the weather in Hong Kong today is fine, dry and very hot, with light winds, which is unfavorable for pollutant dispersion and results in rising regional pollution level," the EPD said.

The intense sunshine enhances photochemical smog activity leading to rapid formation of ozone and fine particulates in the Pearl River Delta region, it explained. “The high ozone level also promotes the formation of nitrogen dioxide.”

The air pollution levels are expected to remain higher during the next couple of days, the department noted.

According to the Hong Kong Observatory, the weather will remain very hot with weak winds over the coast of Guangdong on the Mid-Autumn Festival and the following day.

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The EPD expects that the regional pollution level affecting Hong Kong will remain higher than normal until the advent of stronger wind.

The AQHIs – an air pollution evaluation information provided hourly by the EPD – are grouped into five categories from low to serious. 

When the AQHI reaches the "serious" level, employers of all outdoor workers are advised to assess the risk of outdoor work and take appropriate preventive measures to protect the health of their employees.