Beijing residents have worn face masks to protect themselves as the city is hit by a rare combination of sand and smog.
Levels of PM2.5, small particles seen to be the most harmful to people's health, reached 248 micrograms per cubic meter at 10:00 a.m. local time on Monday. Readings over 200 are classified as heavily polluted by the authorities.
Levels of PM10, slightly larger particles in the air, reached 150 micrograms per cubic meter.
The polluted air cut visibility on city streets as well.
The Beijing government is now under pressure to solve its air pollution problem.
It has committed to reducing coal use by 11.8 million tons by the end of 2017, compared to 2012 levels. It would reach 70 percent of the target after the closure of the city's last coal-powered station.
Last month, the Huaneng Beijing Thermal Power Plant became the fourth and last coal-fired power station shut down by the government.
Huaneng said the shutdown of the generator, which had an installed capacity of 845,000 kilowatts and a heating capacity of 26 million square meters, would cut coal consumption by 1.6 million tons a year.
The three other power stations had already been replaced with natural gas.
Earlier this month, Beijing Gas Group Co., Ltd, the city's main heating provider, vowed to put an end to coal-powered heating and have all its power fueled by natural gas, as the capital's five-year clean air action plan draws to an end this year.
The company will invest 8.5 billion yuan (over 1.2 billion US dollars) and replace coal-fired heating with natural gas in 336 villages, covering 144,000 households, the company said in a statement.
The move will cut coal consumption by 432,000 tons per year.
By the end of the year, the company aims to end coal-burning heat in four districts, Daxing, Fangzhan, Tongzhou and Fengtai, in the city.