Air pollution in Delhi
The air quality in Delhi, the capital territory of India, according to a WHO survey of 1,650 world cities, is the worst of any major city in the world. It also affects the districts around Delhi  Air pollution in India is estimated to kill about 2 million people every year; it is the fifth largest killer in India. India has the world's highest death rate from chronic respiratory diseases and asthma, according to the WHO. In Delhi, poor quality air irreversibly damages the lungs of 2.2 million or 50 percent of all children.
On 25 November 2019, the Supreme Court of India made statements on the pollution in Delhi saying "Delhi has become worse than narak (hell)". Supreme Court Justice Arun Mishra said that it is better to get explosives and kill everyone.
India's Ministry of Earth Sciences published a research paper in October 2018 attributing almost 41% to vehicular emissions, 21.5% to dust and 18% to industries. The director of Centre for Science and Environment (CSE) alleged that the Society of Indian Automobile Manufacturers (SIAM) is lobbying "against the report" because it is "inconvenient" to the automobile industry.
Air quality index of Delhi is generally Moderate (101–200) level between January to September, and then it drastically deteriorates to Very Poor (301–400), Severe (401–500) or Hazardous (500+) levels during October to December due to various factors including stubble burning, road dust, vehicle pollution and cold weather. In November 2017, in an event known as the Great Smog of Delhi, the air pollution spiked far beyond acceptable levels. Levels of PM2.5 and PM 10 particulate matter hit 999 micrograms per cubic meter, while the safe limits for those pollutants are 60 and 100 respectively.
Delhi's pollution problem is also caused by the factor of animal agriculture, as smog and other harmful particles are produced by farmers burning their crop in other states. About 80 per cent of agriculturally used land is used for animal agriculture, so animal agriculture can also be attributed as a factor in Delhi's air pollution problem. Initiatives such as a 1,600 km long and 5 km wide The Great Green Wall of Aravalli green ecological corridor along Aravalli range from Gujarat to Delhi which will also connect to Shivalik hill range is being considered with planting of 1.35 billion (135 crores) new native trees over 10 years to combat the pollution. In December 2019, IIT Bombay, in partnership with the McKelvey School of Engineering of Washington University in St. Louis, launched the Aerosol and Air Quality Research Facility to study air pollution in India.
Particulate matter levels in Delhi
Air quality or ambient/outdoor air pollution is represented by the annual mean concentration of particulate matter PM10 (particles smaller than 10 microns) and PM2.5 (particles smaller than 2.5 microns, about 25 to 100 times thinner than a human hair).
The world's average PM10 levels, for the period 2008 and 2013, based on data of 1600 cities in 91 countries, range from 26 to 208 micrograms per cubic meter of air (μg/m3), with the world average being 71 μg/m3. 13 of the 25 cities worldwide with the highest levels of PM are in India.
In 2010, the year of the WHO survey, the average PM10 level in Delhi was 286 μg/m3. In 2013, the PM2.5 level was 153 μg/m3. These levels are considered very unhealthy. In Gwalior, the city with the worst air quality in India, the PM10 and PM2.5 levels were 329 μg/m3 and 144 μg/m3 respectively. For comparison, the PM10 and PM2.5 levels in London were 22 μg/m3 and 16 μg/m3 respectively. The PM levels in Delhi have become worse since the WHO survey. In December–January 2015, in Delhi, an average PM2.5 level of 226 μg/m3 was noted by US embassy monitors in Delhi. The average in Beijing for the same period was 95. Delhi's air is twice as bad as Beijing's air. As of October 2017, experts in several monitoring stations have reportedly measured an air quality index (AQI) of 999. According to said experts this is the equivalent of smoking 45 to 50 cigarettes a day. This has led to some government officials, such as Arvind Kejriwal calling the nation's capital a "gas chamber".
Safe levels for PM according to the WHO's air quality guidelines are 20 μg/m3 (annual mean) for PM10 and 10 μg/m3 (annual mean) for PM2.5.
Causes of poor air quality
- Lack of active monitoring and reaction by authorities.
- Lack of political priority.
- Motor vehicle emissions are one of the causes of poor air quality. Other causes include wood-burning fires, fires on agricultural land, exhaust from diesel generators, dust from construction sites, burning garbage and illegal industrial activities in Delhi. Although pollution is at its worst from November to February, Delhi's air misses clean-air standards by a wide margin for much of the year. It is a noxious mix of emissions from its 9 million vehicles, construction dust and burning of waste. On the worst days, the air quality index, a benchmark ranging from zero (good) to 500 (hazardous), exceeds 400.
- The Badarpur Thermal Power Station, a coal-fired power plant built in 1973, is another major source of air pollution in Delhi. Despite producing less than 8% of the city's electric power, it produces 80 to 90% of the particulate matter pollution from the electric power sector in Delhi. During the Great smog of Delhi in November 2017, the Badarpur Power Plant was temporarily shut down to alleviate the acute air pollution but was allowed to restart on 1 February 2018. In view of the detrimental effect to the environment, the power plant has been permanently shut down since 15 October 2018 
- The drift/mist emissions from the wet cooling towers are also a source of particulate matter as they are widely used in industry and other sectors for dissipating heat in cooling systems.
- Although Delhi is kerosene free and 90% of the households use LPG for cooking, the remaining 10% uses wood, crop residue, cow dung, and coal for cooking. (Census-India, 2011)
- Fire in Bhalswa landfill is a major reason for airborne particles in Delhi.
- Heavy metal-rich fire-crackers
- Agricultural stubble burning also affects Delhi's air quality when crops are being harvested.
Effects of poor air quality
Effects on children
2.2 million children in Delhi have irreversible lung damage due to the poor quality of the air. In addition, research shows that pollution can lower children's immune system and increase the risks of cancer, epilepsy, diabetes and even adult-onset diseases like multiple sclerosis. Children are more vulnerable to the negative effects of air pollution as they are growing and developing which means that they breathe a higher rate of air per kilogram of their body weight. They also spend more time outside and are thus more exposed to it.
Effects on adults
Poor air quality is a cause of reduced lung capacity, headaches, sore throats, coughs, fatigue, lung cancer, and early death. During the ongoing Covid 19 pandemic, in case the particulate matter (≤ pp10) is not controlled, the aerosols would work as virus carriers/host in the rapid spread of the pandemic.
Smog in Delhi
Smog in Delhi is an ongoing severe air-pollution event in New Delhi and adjoining areas in the National Capital Territory of India. Air pollution in 2017 peaked on both PM 2.5 and PM 10 levels. It has been reported as one of the worst levels of air quality in Delhi since 1999.
"The Great Smog" also led to cancellation and delay of public transport, primarily trains and flights, causing many hindrances to the people.
- Source of pollution
The current majority of analysis sources are hinting towards colder weather, stagnant winds trapping the various sources of smoke. The primary sources of smoke are stubble burning, lit garbage, road dust, power plants, factories, and vehicles.
Air quality can be measured by the amount of PM 2.5 and PM 10 particulates suspended in the air. On 7 November 2017 the PM 2.5 levels in Delhi shot up to a high 999, much above the recommended 60 micrograms. At the same time, PM 10 shot to 999 (the maximum level for the monitors), instead of the recommended limit of 100.
Again on 8 November 2017 the PM 2.5 levels shot up to 449. At the same time PM 10 shot to 663.
The temperature in New Delhi during this period was from 15 to 29 °C (~66 °F).
During the second day of the third test of Sri Lankan cricket team in India in 2017-18 at Delhi, smog forced Sri Lanka cricketers to stop playing and wear anti-pollution masks. Cricketer Lahiru Gamage reported to have shortness of breath. Nic Pothas, coach of Sri Lankan cricket team, reported that cricketer Suranga Lakmal had vomited regularly due to severe pollution effect on the Delhi ground. There was a halt of play between 12:32 pm to 12:49 pm which caused Indian coach Ravi Shastri to come out aggressively and have a talk with the field umpire David Boon.
A Health Emergency was declared in the capital by the Central Government of India to cope with the extrusive amount of polluted air. The day was declared as a holiday for schools, offices and other government centres.
- Health effects
The government of Delhi has declared a health advisory.
- Chest constriction
- Irritation in eyes
- All Delhi schools will remain shut for the next few days.
- For the next five days, no construction and demolition work will take place in Delhi.
- All diesel generator sets have been banned for the next ten days, except at hospitals and in emergencies.
- The Delhi government will supply power to unauthorized colonies which use diesel generators.
- The coal-based Badarpur power plant will be shut down for ten days. There will be no-fly ash transportation from the power plant.
- The Environment Department will launch an app to monitor the burning of leaves.
- Vacuum cleaning of roads will start on 10 November.
- Water sprinkling will start on all roads from the next following days.
- People should stay at home as much as they can and they should try working from home.
- As per Faster Adoption and Manufacturing of Electric Vehicles in India scheme it is expected by 2030 all vehicles will be Battery electric and Hybrid
- All combustion engined vehicles will be upgraded to BS6 emission standards
- Any vehicle older than 10-15 years or below BS6 emissions will be banned
- By 2021, the entire Delhi Metro is expected to be 100% powered by solar energy
In October 2020, Delhi authorities established a 10-member air pollution control team working in a dedicated conference room. They examine complaints received through the "Green Delhi" mobile app. As of 2020, they also regulate construction dust and ban diesel generators. Air pollution is an issue of special concern during the COVID-19 pandemic because the virus can damage people's lungs and make them less able to cope with pollution.
Longer term measures
Air quality monitoring stations
The Indian Meteorological Department (IMD) has air quality monitoring stations in Mathura Road, IMD Delhi (Jor Bagh area), IGI Airport, IITM Delhi, Guru Teg Bahadur Hospital (Ghaziabad area), Dhirpur, Delhi Technological University, Pitampura, Shaheed Sukhdev College of Business Studies (Rohini), Aya Nagar (Gurgaon), and Noida. The air pollution monitor of the U.S. Embassy in New Delhi covers the area of Chanakyapuri.
Response of expatriates
To contend with the poor air quality, embassies and international businesses in Delhi are considering reducing staff tenures, advising staff to reconsider bringing their children to Delhi, providing high-end air purifiers, and installing expensive air purifiers in their offices.
In December 2017 during a test match between Sri Lankan and Indian cricket teams in New Delhi, Sri Lanka players began to feel breathing problems and several players vomited both in the restrooms and in the field and had to use face masks until the match was stopped. However Indian side was unsympathetic to the Sri Lankan team, Hindi commentators joked on air that Sri Lankan players were using masks to hide their faces after having taken the beating of their lives while prominent people lauded Indian cricket team's nationalism on Twitter claiming that they sacrificed their health to entertain the crowd that had turned up, while Virender Sehwag called it an act to stop Virat Kohli from scoring a triple century. However, after the resumption of the match Indian player Mohammad Shami also vomited. Before Shami had said that while pollution levels are a concern, Indian players are used to such conditions. In the opinion of the Indian Medical Association president the match should never have taken place and the ICC should have a policy on pollution.
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