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Delhi no more the most polluted city in the world: WHO report

The World Health Organisation's (WHO) urban air quality database released on Thursday showed that Delhi is no more the most polluted city in the world.

The database revealed that Delhi now ranks 11th among 3,000 cities in 103 countries in terms of PM 2.5 (fine, particulate pollution) and 25th in terms of PM 10 (coarse pollution particles) levels.

This is without doubt a remarkable improvement since 2014 when Delhi was ranked the most polluted city in terms of PM 2.5 levels. At that time only 1600 cities were monitored by WHO but this time the UN body added 1400 more cities.

According to the database, Zabol in Iran is the most polluted city in the world followed by Gwalior and Allahabad in terms of PM 2.5, which is associated with more serious health impacts than PM 10. Patna and Raipur rank 6th and 7th. Four Indian cities are there in the list of world's ten most polluted cities, 10 out top 20 are also in India. In WHO's 2014 report, 13 out of 20 most polluted cities were in India.

The report showed that Delhi's annual PM 2.5 mean for 2013 (second half) is 122 micrograms per cubic metres compared to 153 micrograms per cubic metres as per WHO's previous report. Data from various government and research organisations were used by the WHO to compile the database. The WHO also measured annual mean concentrations of particulate matter (PM 10 and PM 2.5) and "aims at representing an average for the city or town as a whole, rather than for individual stations. Years of measurements range from 2010 to 2015, unless the latest available data was older."

It is crucial for city and national governments to make urban air quality a health and development priority," said WHO's Dr Carlos Dora. "When air quality improves, health costs from air pollution-related diseases shrink, worker productivity expands and life expectancy grows. Reducing air pollution also brings an added climate bonus, which can become a part of countries' commitments to the climate treaty," he added.

"Delhi has improved. Ahmedabad has stabilized and Patna has worsened. We have seen that Delhi has managed to arrest the declining air quality trend in 2015. Air policy action has started kicking in - with an environment compensation charge on on trucks, action against other sources. We are responding to action but the levels are still very high in the city, it only shows that action has to be sustained to meet clean targets," said Anumita Roy Chowdhury, executive director, Centre for Science and Environment (CSE).