- Avoid or reduce outdoor exercise and spend more time indoors, says environment department
- Top alert level recorded in parts of the city on Wednesday, with children, elderly and those with certain illnesses in built-up areas most at risk
Air pollution reached its highest alert level in parts of Hong Kong on Wednesday after the government warned of a "serious" risk to public health and advised people to avoid outdoor activity.
The Environmental Protection Department released a statement earlier on Wednesday afternoon saying pollutant levels had been rising since the morning, with the Air Quality Health Index expected to reach the worst category at some monitoring stations.
Later in the afternoon, two official sites in the New Territories recorded the risk to public health as "serious", which is at the top of the five-tier scale.
"Under the influence of the outer subsiding air of tropical cyclone Danas, the weather in Hong Kong today is hazy with sunny periods and light wind," the statement said.
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"Hong Kong is being affected by an air mass with higher background pollutant concentrations. Higher than normal levels of ozone and particulates have been recorded in the territory since noon."
It added high levels of ozone promoted the formation of nitrogen dioxide, particularly in urban areas and at the roadside.
At 2pm, 11 out of 16 monitoring stations, including general stations in 13 districts and three roadside sites on Hong Kong Island and Kowloon, reported the health risk from the pollution as "very high", the second highest on the scale.
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The areas affected included Central and Western district, Yuen Long, Kwai Chung, Tun Muen, Tung Chung and Tai Po.
At 4pm, two stations in Yuen Long and Tuen Mun recorded a "serious" health risk from pollution.
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The department advised members of the public to reduce or avoid outdoor physical exertion to minimum levels and to cut the time they spent outside, especially in areas with heavy traffic, where the health risk is very high for children, the elderly and people with existing heart or respiratory illnesses.
Hong Kong Observatory forecast a southwesterly air stream to bring a few showers and thunderstorms to the south China coast and ease the pollution later in the week.
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