Story highlights At least 24 cities have issued air pollution alerts

The fog and smog should begin to disperse Wednesday

(CNN) As if recent red alerts for smog weren't bad enough, China has now issued its first-ever red alert for fog to go along with them.

More fog envelops cars crossing a bridge in Yangzhou, in China's eastern Jiangsu province.

China's national observatory issued the fog alert Tuesday in a number of northern and eastern regions.

That followed some 24 cities issuing red alerts for air pollution . Red is the most serious level in the country's warning system.

Commuters wear masks on a polluted day in Beijing on December 20. Hundreds of flights were canceled and road and rail transport ground to a halt under the low visibility.

Through Wednesday, thick fog in parts of the Beijing-Tianjin-Hebei region will reduce visibility to less than 500 meters (about 547 yards), as well as in the provinces of Henan, Shandong, Anhui and Jiangsu, the National Meteorological Center said. In extreme cases, visibility may fall below 50 meters (55 meters) in those regions.

Beijing's cental business district was clouded in pollution December 31 during an orange alert -- not as bad as what came in the new year.

The center also renewed an orange alert for smog in the same period in northern, eastern and central China, with smog continuing to blanket the regions since Friday.

On New Year's Day, Beijing was under a dark cloud of toxic particles 20 times higher than the maximum level recommended by the World Health Organization.

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