It was one of the worst bouts of air pollution in the area, cutting visibility and causing major disruption in transportation and daily activities.

[2] China limited the fine particulate matter level, and the Chinese government officials' assessment index included improving the environment for the first time.

The fastest growing fog and smog days occurred in the Pearl and Yangtze River Delta regions, which are the most industrialized areas.

The report calls for urgent implementation of regional joint prevention and control measures to effectively solve the air pollution crisis.

[citation needed] The lingering smog also left the air qualities in neighboring cities, such as Nanjing, Jiaxing, at seriously polluted levels.

Research shows that prevailing winds blew low-hanging air masses of factory emissions (mostly SO2) towards the east coast of China.

[10] In 2011, a factory manufacturing solar panels in Zhejiang province had been shut down because of toxic emissions of fluorine polluting air and water, sickening nearby residents.

With such a high concentration of air pollutants, government authorities warned residents of health symptoms, such as coughing and headaches.

[14] From 5 to 6 December, Nanjing's air pollution stayed at red alert, suspending classes in all middle and primary schools and kindergartens.

[19] Officials blamed the dense pollution on lack of wind, automobile exhaust emissions under low air pressure and coal-powered district heating system in North China.

On 12 February 2014, China's cabinet announced that government will implement a series of measures aimed at shifting the primary energy source from coal to natural gas and renewables.

[22] PM2.5, a particulate matter with a diameter of 2.5 micrometers or less, is one of the major components of the air pollution in Eastern China, contributing to the growing smog problem in large areas across cities.

PM2.5 is a byproduct of the process of coal burning from power stations and produces significant amounts of sulfate, black carbon, ammonium, and nitrate.

[25] More importantly, such chemicals, along with organic carbon released from coal burning, may react with each other in the air, creating more toxic, harmful particles made of SO2−4 and NO−3.

[28] Pollution from China has already affected other countries, and some ozone-forming particles have travelled across the Pacific Ocean to the United States, contributing to a relatively high level of ozone on the American West Coast.

While these particles, along with other ozone-related chemicals, can be carried up to 30,000 feet above the ground, researchers in the United States predict that these pollutants may play a bigger role in the near future.

For example, Chinese researchers have found that smog in Beijing contains significant amounts of inhalable microbial allergens and pathogenic species, which increase the risk of respiratory diseases.