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    By Lalit Maurya and Subhojit Goswami   |Back to the Down To Earth

Air pollution has been Delhi’s persistent enemy. It rears its head at the onset of winter when heavy smog envelopes the national capital, reducing visibility and causing physical discomfort. While firecrackers and burning of crops in neighbouring states worsen the quality of air that’s already toxic, meteorological conditions make the air thick and stagnant, hence trapping the pollution close to the ground.

As Delhi chokes on bad air, the rise in air pollution in other Indian cities is equally disconcerting. The analysis of the Central Pollution Control Board’s data since 2002 showed that all major cities in north and central India— Gwalior, Kanpur, Ludhiana, Gwalior and Surat—have recorded higher pollution rise in percentage terms between 2002 and 2014 as compared to Delhi.

  Select map and click on bubble to see details (Bubble size shows the pollution level of cities)

The WHO guideline for 24-hour average PM 2.5 levels is 25 µg/m³. With an annual average PM 2.5 level of 122 µg/m³, Delhi’s air is the worst among global megacities with dense populations.

AQI Remark Color Code Possible Health Impacts
0-50 Good   Minimal impact
51-100 Satisfactory   Minor breathing discomfort to sensitive people
101-200 Moderate   Breathing discomfort to the people with lungs, asthma and heart diseases
201-300 Poor   Breathing discomfort to most people on prolonged exposure
301-400 Very Poor   Respiratory illness on prolonged exposure
401-500 Severe   Affects healthy people and seriously impacts those with existing diseases

Source: Central Pollution Control Board; Breakpoint figures in micrograms per cubic meter (µg/m³)

☞    Most polluted cities in India (bubble size shows the value of PM 10 annual mean, ug/m3)

☞  Database of polluted cities in India (use filters and search to see details)