Particulate pollution, which health officials say is the most destructive to lungs, was measured at over 500 micrograms per cubic meter, with some downtown Harbin locations reaching as high as 1,000.
The World Health Organization says a reading over 300 is hazardous and recommends a daily level of no more than 25.
“The impact of air pollution on people will be gradual. There won't be a sudden outbreak of symptoms, but normally three to five days after the smoggy weather occurs, there is a peak in the number of people seeing doctors,” Deng Ying, a doctor at the Second Affiliated Hospital of Harbin Medical University told the official Xinhua news agency.
Beijing was enveloped in hazardous smog last winter when the particulate concentration soared above 900.
China has announced plans over the past few years to tackle the pollution problem in the increasingly industrialized country, but little apparent progress has been made.
Photo: China Daily