section_path: Cityscape/Environmental issues/Air quality
section_name: Air quality
paragraph_text: Air quality
  
  Joint research between American and Chinese researchers in 2006 concluded that much of the city's pollution comes from surrounding cities and provinces. On average 35–60% of the ozone can be traced to sources outside the city. Shandong Province and Tianjin Municipality have a "significant influence on Beijing's air quality", partly due to the prevailing south/southeasterly flow during the summer and the mountains to the north and northwest.
  
  In preparation for the 2008 Summer Olympics and to fulfill promises to clean up the city's air, nearly US$17 billion was spent. Beijing implemented a number of air improvement schemes for the duration of the Games, including halting work at all construction sites, closing many factories in Beijing permanently, temporarily shutting industry in neighboring regions, closing some gas stations, and cutting motor traffic by half by limiting drivers to odd or even days (based on their license plate numbers), reducing bus and subway fares, opening new subway lines, and banning high-emission vehicles. The city further assembled 3,800 natural gas -powered buses, one of the largest fleets in the world. Beijing became the first city in China to require the Chinese equivalent to the Euro 4 emission standard.
  
  Coal burning accounts for about 40% of the PM 2.5 in Beijing and is also the chief source of nitrogen and sulphur dioxide. Since 2012, the city has been converting coal-fired power stations to burn natural gas and aims to cap annual coal consumption at 20 million tons. In 2011, the city burned 26.3 million tons of coal, 73% of which for heating and power generation and the remainder for industry. Much of the city's air pollutants are emitted by neighboring regions. Coal consumption in neighboring Tianjin is expected to increase from 48 to 63 million tons from 2011 to 2015. Hebei Province burned over 300 million tons of coal in 2011, more than all of Germany, of which only 30% were used for power generation and a considerable portion for steel and cement making. Power plants in the coal-mining regions of Shanxi, Inner Mongolia and Shaanxi, where coal consumption has tripled since 2000, and Shandong also contribute to air pollution in Beijing. Shandong, Shanxi, Hebei and Inner Mongolia, respectively rank from first to fourth, among Chinese provinces by coal consumption. There were four major coal-fired power plants in the city to provide electricity as well as heating during the winter. The first one (Gaojing Thermal Power Plant) was shut down in 2014. Another two were shut in March 2015. The last one (Huaneng Thermal Power Plant) would be shut in 2016. Between 2013 and 2017, the city planned to reduce 13 million tons of coal consumption and cap coal consumption to 15 million tons in 2015.
  
  The government sometimes uses cloud-seeding measures to increase the likelihood of rain showers in the region to clear the air prior to large events, such as prior to the 60th anniversary parade in 2009 as well as to combat drought conditions in the area. More recently, however, the government has increased its usage of such measures as closing factories temporarily and implementing greater restrictions for cars on the road, as in the case of " APEC blue " and "parade blue," short periods during and immediately preceding the APEC China 2014 and the 2015 China Victory Day Parade, respectively. During and prior to these events, Beijing's air quality improved dramatically, only to fall back to unhealthy levels shortly after.
  
  On 8 and 9 December 2015 Beijing had its first smog alert which shut down a majority of the industry and other commercial businesses in the city. Later in the month another smog "red alert" was issued.
  
  According to Beijing's environmental protection bureau's announcement in November 2016, starting from 2017 highly polluting old cars will be banned from being driven whenever Smog "red alerts" are issued in the city or neighboring regions.
  
  In recent years, there has been measurable reductions in pollutants after the "war on pollution" was declared in 2014, with Beijing seeing a 35% reduction in fine particulates in 2017 and further reduction by 2020. The primary factors behind this reduction were replacing coal power with natural gas and cleaning up polluting industrial facilities in the Beijing area.
  
  Beijing's annual average concentration of major airborne fine particulate matter, or PM2.5, declined to 30 micrograms per cubic meter in 2022, the best air quality for the city since 2013.