Officials in Harbin, China closed down airports, public transportation as well as many schools on Monday when visibility became dangerously low very low due to smog.

A particulate matter index (PM2.5) gave a reading of 1,000 in Harbin, population 11 million.
The World Health Organization says a daily level of 20 is safe while anything about 300 is hazardous to your health.

According to MSN, the cause is "the first day of the heating being turned on in the city for winter."

Although the government has wanted to address the problem of air pollution for years, it has made very little progress which has brought up inequality issues between the social classes in China.

Now other parts of China are experiencing increasingly high levels of air pollution. Therefore, China has instituted a color-coded alert system to handle these issues.