Kai Tak Cruise Terminal in Kowloon in early January (upper photo) and on January 23 (lower). Photos: Asia Times, Google Maps

Air pollution in Hong Kong worsened on Monday for the second time in five days, reaching the highest level of “serious” in three districts in the afternoon.

At 5pm, Yuen Long and Tuen Mun in the New Territories and Tung Chung on Lantau Island reached the “serious” health risk, and their readings for PM 2.5 – fine airborne particles with a diameter of 2.5 microns or less – were seven to eight times the levels recommended by the World Health Organization.

As recorded by pollution-monitoring stations across the city, downtown districts Central and Causeway Bay on Hong Kong Island and Kowloon’s Mong Kok, as well as 10 other districts, reached the “very high” health-risk level, Sing Tao Daily reported.

The weather on Monday was hazy with sunny periods and light winds, which hindered effective dispersion of air pollutants and led to their accumulation in Hong Kong and the Pearl River Delta region since Sunday, according to a release from the city’s Environmental Protection Department.

Sunshine also enhanced photochemical smog activity.

According to the Hong Kong Observatory, an intense northeast monsoon will start to affect the south China coast midweek. It is expected that pollution levels will improve after the wind strengthens.