Chinese business capital Shanghai, along with some parts of the Yangtze River Delta, have been hit with heavy smog on Tuesday.

Officials believe that the cold front that came from the north carried the smog. Because of this poor air quality, the municipal government issued a yellow alert - the third highest level warning.

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Shanghai factories were told to reduce their production. Schools were advised to avoid outdoor activities, or to let pupils stay outside the classrooms for long periods of time.

Residents, who were either sick, elderly or young, were advised to remain inside the home, avoiding any outdoor activity. Windows were also advised to be closed.

The smog arrived in Shanghai a day prior to the closely-watched World Internet Conference, which will be hosted in the city. This event will include a speech to be given by Chinese President Xi Jinping. Those expected to be attending include tech industry giants and global leaders from countries such as Pakistan and Russia.

The smog that fell over Shanghai limited visibility. The city's air quality index reached levels higher than 300, which is considered to be very dangerous to human health. Exposure to such will have long-term impacts on health.

According to the U.S. Department of State, PM 2.5 levels rose up to 281, the highest level that Shanghai had since mid-January. PM 2.5 particles are dangerous tiny pollutants that cause asthma and other respiratory diseases.

As regions to the north have tightened pollution regulations for production plants such as steel mills and cement plants, production is moving south. This could also be contributing to the smog that fell down on the city.

This current air pollution problem is not only limited to Shanghai. Reports say it has been causing problems nationwide, along with clogged waterways and heavy metals in the soil.

TagsShanghai Smog, Beijing Air Pollution, Shanghai Air Pollution, World Internet Conference Wuhan