BEIJING — Visibility shrank to less than 50 yards and small-particle pollution soared to a record 40 times higher than an international safety standard in one northern Chinese city as the region entered its high-smog season.
Winter typically brings the worst air pollution to northern China because of a combination of weather conditions and an increase in the burning of coal for homes and municipal heating systems, which usually starts on a specific date.
For the large northern city of Harbin, the city’s heating systems kicked in on Sunday, and on Monday visibility there was less than 50 yards, according to state media.
‘‘I couldn’t see anything outside the window of my apartment, and I thought it was snowing,’’ Wu Kai, 33, mother of a baby boy, said in a telephone interview from Harbin.
She said her husband went to work in a mask and he could barely see a few yards ahead of him. His usual bus had stopped running.
‘‘It’s scary, too dangerous,’’ she said. “How could people drive or walk on such a day?’’
The density of fine particulate matter was well above 600 micrograms per cubic meter — including several readings of exactly 1,000 — for several monitoring stations in Harbin. A safe level under World Health Organization guidelines is 25 micrograms per meter.
The manager for US jazz singer Patti Austin, meanwhile, said the singer had canceled a concert in Beijing because of an asthma attack probably due to pollution.