Delhi's air worst among 381 cities
The World Bank report titled - ' Leveraging Urbanization in South Asia', stated air pollution as a major challenge for most cities in the region.
Delhi was identified as the worst polluted among 381 cities from developing countries and 19 out of 20 most polluted cities are from South Asia.
The report said Delhi recorded air pollution three times higher than Beijing.
7 May 2015: WHO report on Delhi's pollution
According to a WHO study, Delhi is the most polluted city in the world in terms of air quality.
Delhi has the highest concentration of PM 2.5 - particulate matters less than 2.5 microns- form of air pollution, which is considered the most serious.
The report covered the period from 2008 to 2013, with the majority of values for the years 2011 and 2012.
Fact: Particulate matter
Air quality is represented by the annual mean concentration of fine particulate matter (PM10 and PM2.5, particles smaller than 10 or 2.5 microns). Delhi's air has PM2.5 concentrations of 153 micrograms and PM10 concentrations of 286 micrograms, which is much more than the permissible limits.
8 May 2015: India rejects WHO report
India rejected the WHO report on Delhi's air quality. Government scientists said that U.N. agency had overestimated levels in the capital.
"Delhi is not the dirtiest and certainly it is not that dangerous as projected," said a member secretary of the Central Pollution Control Board of India.
Chief scientist at Indian Institute of Tropical Meteorology also said that Delhi's air was better than Beijing's.
24 Jun 2015: Ten worst and ten most polluted countries
Pakistan, Afghanistan, Bahrain, Senegal, Qatar, Bangladesh, UAE, Mongolia, Egypt, and India, are the 10 most polluted countries in the world with Pakistan recording the highest level over all of the 91 countries in the WHO air pollution database.
Going by the WHO report, Iceland, Australia, Canada, Brunei, Finland, Denmark, Estonia, New Zealand, Sweden, Ireland and Luxembourg are the least polluted countries in that order.
22 Jul 2015: NGT slams Delhi government regarding improper vehicle inspection
The National Green Tribunal slammed Delhi government over its 'incomplete' inspection report on air pollution caused by vehicles entering the capital.
NGT pulled up the government for testing vehicles on only two parameters- opacity of smoke and carbon dioxide emissions.
The inspection requires inspection based on seven parameters. This includes measuring particulate matter which has been an issue as suggested by the WHO report.
Fact: Most polluted Indian cities
The top polluted Indian cities as per the WHO report in descending order include Delhi (153 micrograms per cubic metre) followed by Patna (149), Gwalior (144) and Raipur (134).
25 Sep 2015: Delhi's air worst among 381 cities
6 Oct 2015: SC asks for plan to counter pollution
Supreme Court provided New Delhi 3 days devise a policy to "clean up the air in a city ranked by the World Health Organisation as the most polluted in the world".
Recognising that pollution from commercial vehicles was most threatening, the SC asked Centre and Delhi government for a "quick positive response" on the feasibility of a pollution tax on them.
9 Oct 2015: Approved by SC: Pollution tax on vehicles in Delhi
SC has levied a pollution tax of Rs.1300 on big trucks and Rs.700 on LCVs which use the Delhi route to travel to other states; it will also be applicable on trucks transporting goods to Delhi.
This experiment will be tried for 4 months and its impact will be assessed.
The amount collected would be utilized by Delhi government for improving public transport.
3 Dec 2015: Delhi government asked to discuss pollution abatement measures
With Delhi experiencing smog for 5 days in a row, the state government has been asked by the National Green Tribunal (NGT) to convene an emergency meeting and discuss measures to control pollution.
The government is also required to release a notification with the control measures already taken.
The bench said that PM2.5 and PM10 levels are beyond prescribed limits which cannot be permitted.
3 Dec 2015: HC compares Delhi's pollution levels to gas chamber
Noting that the current air pollution levels in the national capital have reached "alarming" proportions, Delhi High Court observed that it was akin to "living in a gas chamber".
The court directed the Centre and State government to present comprehensive action plans to combat it.
The court took up the issue of air pollution in Delhi as a suo moto PIL earlier this year.
4 Dec 2015: New system for private vehicles to curb Delhi's pollution?
Delhi CM Arvind Kejriwal called for an emergency meeting on rising pollution in Delhi, a day after the High Court's observations.
The measures announced post-meet include massive plantation drive along all arterial roads across the cities to curb the spread of dust.
It was also announced that from 1 Jan, private vehicles with odd and even number plates are to ply on alternate days.