With the smog enveloping Beijing already on its sixth consecutive day, the World Health Organisation said the current levels of air pollution in China has reached a crisis.
"Of course, on days where pollution levels reach or even exceed the scale we are very concerned and we have to see this as a crisis," Bernhard Schwartlander, the WHO representative in China, said.
He implied sicknesses and number of deaths are surely to abound in the coming years in the developing economy.
"There's now clear evidence that, in the long term, high levels of air pollution can actually also cause ... lung cancer."
On Tuesday night, readings from the U.S. Embassy in Beijing showed levels of PM2.5 averaged 452 microgrammes per cubic metre over a 24-hour period. WHO has always stipulated and recommended a 25 microgrammes per cubic metre level. Tuesday night's readings was way above 18 times than WHO's recommendations.
"We know it has an impact on health, but we don't know yet how much," Shin Young-Soo, the WHO's Western Pacific regional director, said.
On Tuesday, Chinese President Xi Jinping, along with other officials of the Communist Party of China (CPC), braved the smoking and hazardous smog by making a surprise visit to a tourist area. Without a face mask, Mr Xi walked along the lanes of Nanluogu Xiang with its bars, cafeterias and curio shops.
Dressed in trademark black long jacket and trousers, Mr Xi even stopped to chat with pedestrians which included the locals and a handful of foreign tourists. He also visited families living in the city's signature old-styled courtyard, or hutong, homes.
China's National Meteorological Centre forecast more smog pollution ahead for the affected areas.
"From Tuesday to Wednesday, moderate smog will shroud Beijing, Tianjin, Hebei, Shanxi, Shandong, Henan, Shaanxi and Liaoning, where weather conditions will not be favorable for the dispersion of pollutants. Some of those regions will see heavy smog," the agency said in a statement.
Around 980,000 square km of central and eastern China are under the smog cover, according to local reports. Of that, 800,000 square km were heavily polluted, including Beijing and the provinces of Hebei, Shanxi and Liaoning.
Xinhua News Agency said on Tuesday that 147 industrial companies have cut or suspended production to curb the current pollution.
In Liaoning and Shandong provinces, expressways had to be closed as visibility fell to less than 50 metres, Xinhua said.