Air pollution reached dangerous levels in Hong Kong on Sunday, creating a “very high” health risk after a Northeastern monsoon swept smog from the mainland into the city.

Photo: HKO webcam.

At around 6:30pm Sunday, the Environmental Protection Department recorded Air Quality Health Index readings of 8 in the Central/Western district, with highs of 10 in Tuen Mun and Tung Chung. The public were advised to reduce the time of their stay outdoors.

Harmful air pollution, which is measured by the amount of PM2.5 particles found in the atmosphere, registered readings of 193 micrograms per cubic metre in Causeway Bay, and an average of 172 for the city. The reading is far beyond the The World Health Organisation safety limit of 25, or even Hong Kong’s limit of 75.

A spokesperson for the Environmental Protection Department has said that recent sunshine “enhances photochemical smog activities and the formation of ozone.” Furthermore, the relatively light wind has hindered the effective dispersion of pollutants.

Monday lunchtime. Photo: HKO webcam.

The Hong Kong Observatory predicts that pollution levels will remain high, until a monsoon brings in cooler and windier weather later in the week.

In Beijing on Sunday, PM2.5 readings reached 482, however the US Embassy said its readings well surpassed 500, the level at which the scale tops out.