China's capital Beijing and the neighbouring provinces will be affected with the fresh bout of smog following a considerable rise in the pollution levels, the China National Environmental Monitoring Centre warned today. The Beijing-Tianjin-Hebei region and Shandong, Shanxi, Henan provinces will be hardest hit from January 12 to 17. Beijing and Tianjin issued orange alerts yesterday for air pollution in the coming days, advising children and the elderly to stay indoors. Under China's four-tier warning system, red is the most severe, followed by orange, yellow and blue. Certain construction activities were suspended and heavy-duty vehicles were pulled off the road, state-run Xinhua news agency reported. The alert, the second highest level, will come into effect in Beijing from tomorrow and last until Monday, said the city's air pollution emergency response office. From January 13 to 15, parts of the Beijing-Tianjin-Hebei region, southern Shanxi, western Shandong as well as northern Henan are forecast to see severe air pollution, with the density of PM2.5, the major air pollutant, estimated to exceed 250 micrograms per cubic meter of air, said the Ministry of Environmental Protection. The air will gradually improve on January 16, but worsen again the next day. The smog will be dispersed when a cold front arrives on January 18, the ministry said. According to the local air pollution emergency response plan, an orange alert should be issued when the average air quality index is forecast to exceed 200 for three consecutive days and one of those days is forecast to be over 300, the report said.