By Lin Meilian

A weather expert said that heavy fog, which often delays flights and causes economic problems, should be classified a natural disaster.

"Thick fog that delays air and rail services, causes traffic accidents and blocks expressways has become a big headache of modern transportation," Zhang Mingying, an expert with the Beijing Meteorological Station, told the Global Times Thursday. "Therefore, it should be one of the natural disasters."

Heavy fog is when visibility is less than 1 kilometer. Dense fog with visibility lower than 500 meters should be considered a natural disaster, Zhang said.

Zhang's remarks followed an alert for thick fog issued Thursday by the National Meteorological Center. The fog has continued to blanket Central and Southern China.

It said visibility was expected to be less than 200 meters in some places and advised people to cut down on outdoor activities.

The thick fog delayed 80 flights and stranded more than 3,000 passengers at the airports in Shanghai, the Xinhua News Agency reported Thursday. And in the neighboring Zhejiang Province, another 3,000 passengers were stranded as dozens of flights were delayed.

It could be worse.

A major accident occurred in Hebei Province early November after nine cars smashed into each other in thick fog.

Zhang said the losses that occur from dense fog is not as obvious as those from earthquakes or tsunamis but people should not underestimate its power.

"In some polluted places in the country, thick fog and pollution are like twins," he said. "Heavy smog that contains pollutants worsens the air quality."

"Same with other natural disasters, thick fog is beyond our control," He added. "We cannot ignore, remove or stop it, but we can predict it and learn how to live with it."

However, not everyone was quick to support the move to label fog as a natural disaster.

Yang Liu, a driver in Sichuan Province, where dense fog is frequent, told the Global Times Thursday that thick fog was hardly the same as a disaster.

"Thick fog causes shutting down the highways, but what does the earthquake cause? Severely damaged highways," he added.