Weather

The mixture of natural fog and unnatural smog started accumulating over the first weekend of December 2013. In Shanghai, the Air Quality Index (AQI) crossed the threshold of 300 on 2 December.^{[citation needed]} The lingering smog also left the air qualities in neighboring cities, such as Nanjing, Jiaxing, at seriously polluted levels. The National Meteorological Center (NMC) issued yellow alert for smog and fog, the third most serious alert in China's four-tiered system.^[5] PM_2.5 particulate levels reached their highest point on 6 December 2013, with Shanghai reaching a high of 507.^[6] The U.S. Embassy categorizes air quality readings over 300 as hazardous to all humans, not just those with heart or lung ailments.

According to a NASA Terra Satellite image, the thick haze stretches over Eastern China, across a distance of around 1,200 kilometres (750 mi).^[7] The polluted air appears gray on the image and most of the pollution is trapped in the lower boundary layer of a few hundred meters.

Causes

Coal burning is a primary source of fine particle air pollution. It increased as the weather worsened during winter months and residents burned more coal to keep warm. This increased the amount of sulphate and nitrate (results of coal combusting), which led to higher PM_2.5. Research suggests that 41% of the carbon that made up these high PM_2.5 levels in Shanghai were also from coal burning.^[8]

Additionally, there were pollution from industrial sources. Jiangsu, Anhui, Shandong, Henan and many eastern provinces are heavy coal-burning regions. Research shows that prevailing winds blew low-hanging air masses of factory emissions (mostly SO₂) towards the east coast of China.^[9] Regional transportation also had a significant impact on air quality.

The State Environmental Protection Administration investigates tens of thousands of polluters every year, shutting down thousands of the worse offenders, but has failed to reach its target of reducing emissions by 2 percent.^[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.^[11]

Shanghai

Air in Shanghai was reported to have a strange taste – astringent and smoky, with an aftertaste of earthy bitterness.^[12] It was possible to feel the dust-like particulate matter on tongues.

With such a high concentration of air pollutants, government authorities warned residents of health symptoms, such as coughing and headaches. Citizens were advised to wear protective masks and use air purifiers. Many sanitation workers were required to wear dust masks during work early in the morning. Schools were closed as the government ordered children to stay indoors and reduce outdoor activities as much as possible.

Construction work was halted, and authorities pulled nearly one-third of government vehicles from the roads. A majority of inbound flights were cancelled and more than 50 flights were diverted at Shanghai Pudong International Airport.^[13]

Nanjing

The heavy smog greatly polluted central and southern Jiangsu Province, especially around Nanjing, capital of East China's Jiangsu province.^[14] AQI remained at "severely polluted" for five straight days, "heavily polluted" for nine, and hit a record-breaking value of 331. PM₁₀ also went over 500 at times.^[15] On 3 December 2013, levels of PM_2.5 particulate matter averaged over 943 micrograms per cubic metre,^[16] decreasing to over 338 micrograms per cubic metre on 4 December.^[17] Between 3:00 pm, 3 December and 2:00pm, 4 December local time, several expressways from Nanjing to other Jiangsu cities were closed, stranding dozens of passenger buses in Zhongyangmen bus station.^[14] From 5 to 6 December, Nanjing's air pollution stayed at red alert, suspending classes in all middle and primary schools and kindergartens. Experts say these figures indicate high levels of dust on construction sites. Children's Hospital outpatient services increased by 33 percent; the general incidence of bronchitis, pneumonia, upper respiratory tract infection increased significantly.^[18] The smog dissipated 12 December.^[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.^[20]

Jiangxi

Visibility was reduced to less than 50 meters. Many highways in East China's Jiangxi province were closed.^[21]

Bacteria in PM_2.5

Scientists are still trying to understand the microorganisms within PM_2.5 particles and how they are spread through pollutants. Research indicated that many kinds of pathogens and bacteria can be spread through PM_2.5 smog and cause diseases. 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.^[30] The same study also reported that among all the microorganisms within PM_2.5 particles, 86.1% are bacteria, 13% eukaryota, 0.8% archaea, and 0.1% viruses.^[30] The smog contains a variety of microorganisms such as Actinomycetota, Pseudomonadota, Chloroflexota, Bacillota, Bacteroidota, and "Euryarchaeota". Many of these are not harmful to humans, but some pathogenic microorganisms are carried through smog, and their numbers increase as the pollutant level increases.^[30]

More than 1,300 kinds of microorganisms have been detected on PM_2.5 particles. Because PM_2.5 particles have relatively large surface area, many microorganisms from the soil easily attach to them, spreading them quickly through wind. For example, scientists detected that Aspergillus fumigatus var. fumigatus, a fungus which triggers allergic reactions in the respiratory system, are 1% to 8% of microorganisms found on PM_2.5 particles.^[31]

Index

The United States Environmental Protection Agency (EPA) has developed an Air Quality Index that is used to report air quality. This AQI is divided into six categories indicating increasing levels of health concern. A PM_2.5 concentration lower than 12 μg/m³ indicates good air quality and between 12 and 35 μg/m³ the airquality is moderate. An AQI value over 300 represents hazardous air quality and below 50 the air quality is good.^[32] In December 2013, huge areas of Eastern China reached "hazardous" level for multiple days.