HONG KONG -- The general and roadside monitoring stations of Hong Kong's Environmental Protection Department have recorded a higher than normal pollution level Friday and the health risk category is serious in some places.

At 6 pm, the Air Quality Health Index (AQHI) at Sha Tin and Kwai Chung general stations as well as the three roadside stations reached 10+ while other stations were at 8 or above. The corresponding health risk categories are very high to serious.

The elevated health risk is due to high levels of suspended particulates and nitrogen dioxide brought about by light wind, which has been prevailing over the territory since this morning, and the high level of ozone in the region.

The light wind hinders the effective dispersion of air pollutants and the high level of ozone promotes the formation of nitrogen dioxide, particularly at the street level.

According to the Hong Kong Observatory, a cooler replenishment of the northeast monsoon will reach the coastal areas of Guangdong Province overnight. Under the influence of a strong easterly airstream, there will be a few rain patches over the coast of Guangdong early next week. Until then, it is expected that the pollution would persist at a level higher than normal.

AQHI ranges from 1 to 10 and 10+, and the corresponding health risk categories are low, moderate, high, very high and serious.