Timeline of pollution in Delhi
|Time period||Development summary|
|1980s||The issue of air and water pollution in Delhi enters the Supreme Court's agenda in the late decade, and periodic statements and orders are issued from the bench.|
|1990s||Delhi reaches among the world's worst urban level of air quality. Air pollution's heavy impacts on human health, including infant mortality and asthma, leads to sustained efforts for improvement by Indian civil society. Several small and medium-size industries are relocated from Delhi as a measure to control pollution.|
|2000s||Till mid-decade, busy Central and South Delhi areas are high air pollution zones. From then on, dirty air would spread to even cleaner residential areas.|
|2010s||Emergency plans to tackle the city’s annual crisis are reported to have failed in the last years. Delhi’s pollution levels reach high enough to affect the respiratory and cardiac systems of even healthy people.  The city ranks among the most polluted in the world.|
|Year||Month and date||Pollution type||Type of event||Details|
|1947||Air pollution||India becomes an independent state. At the time, fog in Delhi is rather rare.|
|1950–1951||December–February||Air pollution||Only one foggy day is reported in the winter months in the city.|
|1955||Water pollution||Crisis||Sewage and industrial wastes from the Najafgarh drain cause a famous jaundice episode in Delhi. The Najafgarh drain comes to be known as "sorrow of Delhi"|
|1974||Water pollution||Policy||The Central Pollution Control Board is set up under the Water Act.|
|1982||General||Policy||Delhi passes its first Industrial Policy.|
|1985||Air pollution||Policy||The Supreme Court of India states verdict to deal with the chronic problem of vehicular pollution in Delhi, one of the earliest stand taken by judiciary.|
|1987||Air pollution||Study||A survey estimates that 1172 tonnes of suspended particulate matter, hydrocarbons, sulphur dioxide, nitrogen oxides, carbon monoxide and other poisonous gases are spewed into the air in Delhi by industrial units, the various modes of transport and the power sector.|
|1990 – 2001||General||Policy||A Master Plan of Delhi allows for "light" industry to be set up in residential areas. This creates a leeway for many industries which are not in the hazardous category (H) to start in the areas vacated by the "H" category industries without the necessity for any permission from the Delhi Pollution Control Committee.|
|1993 – 2000||Light pollution||Study||Author Pavan Kumar says New Delhi, along with Telangana, Maharashtra, Karnataka and Uttar Pradesh experienced increase in “very high light pollution intensity” in the period.|
|1994||Water pollution||Policy||The Supreme Court takes suo motu notice of a newspaper report about the pollution of the Yamuna.|
|1995||General||Policy||The Supreme Court of India asks the Delhi Pollution Control Committee to categorize all industrial units in the city according to pollution hazard they pose.|
|1995||Air pollution||Policy||Delhi government introduces catalytic converter in passenger cars as vehicle control measure policy to curb air pollution in the city.|
|1996||Air pollution||46 foggy days are reported in the winter months in Delhi.|
|1996||February||Water pollution||Policy||The Supreme Court of India orders the Delhi state government to construct common effluent treatment plants, which the industries are required to pay for, to reduce water pollution.|
|1996||April||General||Policy||The Supreme Court of India orders the relocation of factories away from residential areas.|
|1997||Air pollution||Study||The annual suspended particulate matter average concentration in Delhi is 339.3 microgrammes per cubic meter.|
|1998||Air pollution||Policy||The Supreme Court of India orders a major transformation of Delhi's transportation system, in response to a public interest petition on air pollution.|
|1998||Air pollution||Policy||Delhi government introduces unleaded petrol as vehicle control measure policy to curb air pollution in the city.|
|2000||Air pollution||Policy||Delhi government introduces reduction of benzene content in fuels and reduction of sulfur content in diesel as vehicle control measure policy to curb air pollution in the city.|
|2003||General||Policy||After Supreme Court order on hazardous waste, stringent actions are prompted by various State Pollution Control Board in Delhi.|
|2003||Air pollution||Delhi wins the United States Department of Energy's first 'Clean Cities International Partner of the Year' award for its "bold efforts to curb air pollution and support alternative fuel initiatives".|
|2007||Air pollution||Study||Study finds that the conversion of buses from diesel to CNG in Delhi helped reduce particulates, carbon monoxide, and sulfur oxide, while lowering the sulphur content of fuels cut both sulfur dioxide and – due to SO2 converting to sulphates, fine particles (PM10). Another study only identified lower CO as a result of the change to compressed natural gas in Delhi.|
|2009||Water pollution, soil contamination||Policy||Delhi allows the use of only virgin plastic.|
|2011||September||Air pollution||Study||The World Health Organization releases data about urban air. This reveals that Delhi has crossed the maximum PM10 limit by almost 10-times at 198 μg/m3 (micrograms per cubic meter). Emission from vehicle and industrial activities are found to be linked with outdoor as well as indoor air pollution in Delhi.|
|2012||Water pollution, soil contamination||Policy||Delhi completely bans all plastic.|
|2013||Air pollution||74 foggy days are reported in the winter months in Delhi.|
|2013||January||Air pollution, water pollution, soil contamination||Policy||The High Court of Delhi directs the civic authorities of Delhi to shift the biomedical waste incinerator from the residential area in the city to outside.|
|2013||April||Air pollution||Study||Research paper by The Centre for Development Economics at Delhi School of Economics indicates that Delhi Metro helps reduce vehicular air pollution.|
|2014||May||General||Study||The World Health Organization announces New Delhi as the most polluted city in the world.|
|2014||December||Air pollution||Study||The Centre for Science and Environment classifies the air in Delhi as “severely polluted” for over 65 per cent days.|
|2015||December||Air pollution||Study||Study shows that Delhi loses 80 lives to air pollution every day, or approximately 10,000 to 30,000 annual deaths in the city.|
|2015||End of the year||Air pollution||Policy||Severe air pollution in Delhi National Capital Region leads to a number of Supreme Court rulings, one banning the sale of diesel cars in the area with engine displacements greater than 2.0 L from January 1 to 1 April 2016.|
|2016||November||Air pollution||Crisis||Air pollution in Delhi reaches 16 times above safe levels, and the Delhi government declares an emergency.|
|2017||November||Air pollution||Crisis||A public health emergency is declared by the Indian Medical Association in Delhi as air quality index breached 999, likened to smoking 50 cigarettes a day. Air pollution raises to over 710 micrograms per cubic meter, more than 11 times the World Health Organisation’s safe limit.|
|2017||November 17||Air pollution||Policy||The government of Delhi launches the odd-even rule in an attempt to reduce pollution in the nation's capital. It is based on the Odd-Even rationing method: This means that cars running with number plates ending in Odd digits could only be driven on certain days of the week, while the Even digit cars could be driven on the remaining days of the week.|
|2017||November 25||Air pollution||Policy||The Supreme Court of India bans the sale of firecrackers in Delhi to alleviate pollution.|
|2017||December||Air pollution||Crisis||During a test match between Sri Lankan and Indian cricket teams in New Delhi, Sri Lanka players begin to feel breathing problems and several players vomit both in the rest rooms and in the field and have to use face masks until the end of the match.|
|2018 – 2019||November 1 2018 – January 6 2019||Air pollution||Policy||According to report, toxic levels of air pollution monitored over Delhi almost every week during the period shows that the government’s emergency plans to tackle the city’s annual crisis have failed.|
|2019||March||Air pollution||Study||Study published in journal Nature Sustainability shows that high levels of air pollution in New Delhi during the fall and winter months are largely the result of post-harvest burning of crop residue. Pollution levels from crop burning are so high they rival fossil fuel emissions during peak summer months. The findings contradict the widespread notion that the emission flux between cities and the countryside is mainly one-way, and that the main source of pollution in a megacity is expected to be traffic.|
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