The Environmental Protection Department warns the Air Pollution Index will remain higher than normal in the coming days due to light wind conditions in Hong Kong.

The department recorded very high indices of 125, 102 and 108 at the Tung Chung, Yuen Long and Central-Western general air quality monitoring stations at 3pm today due to high ozone concentrations.

At the roadside, the index at Central station also reached 115 due to high concentrations of nitrogen dioxide.

Under the combined effects of a continental airstream and Typhoon Sinlaku near Taiwan, the weather over south China is fine and hot with light wind. Air pollutants in Hong Kong and the Pearl River Delta region are trapped due to the light wind, and the sunny and hot weather is causing the photochemical reaction of pollutants to form ozone in the region.

At the roadside, pollutants emitted from vehicles cannot disperse effectively under the calm conditions. With the elevated background ozone concentrations, the nitrogen oxides emitted from vehicles are readily oxidised to form nitrogen dioxide.

The Hong Kong Observatory forecasts the weather will remain fine and hot with light wind in the next few days. Dispersion of air pollutants will still be poor and photochemical smog reactions will continue to be active.

With the index in the very high range, people with heart or respiratory illnesses should reduce physical exertion and outdoor activities. Click here for latest air pollution index readings or call 2827 8541.