BEIJING -- China ordered government vehicles off the roads as part of an emergency response to ease air pollution that has smothered the city for three days, while warning the smog will persist until Wednesday.

Hospitals were inundated with patients complaining of heart and respiratory ailments and the website of the capital's environmental monitoring center crashed. Hyundai Motors' venture in Beijing suspended production for a day to help ease the pollution, Xinhua News Agency reported.

Official measurements of PM2.5, fine airborne particulates that pose the largest health risks, rose as high as 993 micrograms per cubic meter in Beijing on Saturday, compared with World Health Organization guidelines of no more than 25. It was as high as 500 at 6 a.m. . Long-term exposure to fine particulates raises the risk of cardiovascular and respiratory diseases as well as lung cancer, said the WHO.

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Exposure to PM2.5 helped cause a combined 8,572 premature deaths in Beijing, Shanghai, Guangzhou and Xi'an in 2012, and led to economic losses of $1.08 billion, according to estimates given in a study by Greenpeace and Peking University's School of Public Health published Dec. 18.

-- Bloomberg News