The Environmental Protection Department has advised people to reduce physical exertion and outdoor activities due to higher than normal pollution levels.
At 4pm today the Air Quality Health Index at some general air monitoring stations and the Causeway Bay roadside air monitoring station reached 8 or above, corresponding to a "very high" health risk.
The department said Hong Kong is being affected by an airstream with higher background pollutant concentrations. The sunshine enhances photochemical smog activities and ozone formation during daytime, and the high level of ozone and light wind conditions have promoted the formation and accumulation of nitrogen dioxide, particularly in urban areas.
It is expected that the AQHI at some general and roadside air monitoring stations may reach the "Serious" level later today.
The Hong Kong Observatory said the weather in the next two days will be warm during the day with light winds. It is expected that higher than normal pollution levels will linger until Sunday.
Children, the elderly and people with heart or respiratory illnesses are advised to reduce physical exertion and outdoor activities.
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