The World’s 20 Most Polluted Cities

Beijing may have declared its second red alert for air pollution, but it is not in the world’s 20 most polluted cities.

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Beijing may be in the midst of its second air pollution red alert, however despite that it doesn’t rank in the world’s top 20 most polluted cities in terms of annual average PM2.5 concentration. PM2.5 is defined as particulate matter with a diameter of less than 2.5 micrometres. The main problem associated with such small particles from combustion and some industrial processes is the health implications. Particles of this size are easily inhaled and can lodge deep in the lungs. According to a report published this month by Greenpeace India, the World Health Organisation has reported that 13 of the top 20 cities are in India. Of the remaining seven, 3 are in Pakistan and the remaining four are in Iran, Qatar, Turkey and Bangladesh.

The report titled “A status assessment of National Air Quality Index (NAQI) and pollution level assessment for Indian cities” based on first of its kind research for India that analysed pollution concentrations from the NAQI network. The portal was started by the Indian Government in April 2015 and it accounts for air pollutants including particulate matter, NO2 (nitrogen dioxide) and SO2 (sulphur dioxide) that have short term impacts. As of 11 November 2015 the portal provides real time data for 16 cities including Delhi, Patna, Faridabad, Bangalore and Mumbai.

In the most polluted Indian cities, a number of months can go by in which not a single day meets the NAAQS. The concentrations of pollutants in a number of cities including Delhi, Ahmedabad, Varanasi and Agra were higher than those in Beijing.

Analysis of the NAQI data for the Greenpeace report confirmed that exposure to very high concentrations of particulates is frequent in most Indian cities and that the National Ambient Air Quality Standards (NAAQS) are almost continually exceeded. In the most polluted Indian cities, a number of months can go by in which not a single day meets the NAAQS. The concentrations of pollutants in a number of cities including Delhi, Ahmedabad, Varanasi and Agra were higher than those in Beijing.

Although the NAQI provides citizens timely and reliable information on air pollution levels, the report highlighted the poor coverage of air pollution monitoring given that most Indian megacities do not have air monitoring stations. Increasing the coverage of all major cities and industrial areas and increasing the number of air pollution monitoring stations in cities that already have them were identified as critical in the report. Only five cities in India have more than one monitoring station.

In terms of health implications, analysis of the NAQI data showed that air pollution reaches concentrations that are both an acute and long term health risk for citizens. The Greenpeace report recommended that air pollution concentrations should be communicated through radio, television and the internet. In doing so, the system would play its part in protecting citizens from potentially hazardous air pollution concentrations by giving advice regarding how they can protect themselves. In addition, the report reiterated the Indian Government’s duty to issue alerts, encourage the use of pollution masks and installing air purification systems in schools, hospitals and other public buildings. 

The data analysis performed for A status assessment of National Air Quality Index (NAQI) and pollution level assessment for Indian cities showed that high air pollution concentrations are a problem across the whole subcontinent. The majority of the air pollution measured in cities is predominantly attributed to emissions from outside the city, and therefore national and regional action is required in association with local measures implemented in Indian cities.

In concluding the report, Greenpeace India was adamant that these eight major steps can be implemented to make the NAQI a more effective tool:

  • making the NAQI national and having at least 3 monitoring stations in each location
  • upgrading manual stations to continuous air quality monitoring stations which feed data into the NAQI portal
  • expanding the distribution and reach of the real time monitoring data through television, radio, newspapers, mobile Apps and web portals
  • issuing real time health advisory as well as the data to give citizens advice on actions they can take depending on the pollution concentration
  • including long term and chronic health impacts from air pollution in the health advisory
  • strengthening emission standards for thermal power plants and other industries to reduce air pollution concentrations
  • make public transport more reliable and safer to encourage a shift away from polluting private vehicles
  • implementing stricter exhaust emission standards for vehicles.

The world’s 20 most polluted cities based on annual average PM2.5 concentrations in order are:

  1. Delhi (India)
  2. Patna (India)
  3. Gwalior (India)
  4. Raipur (India)
  5. Karachi (Pakistan)
  6. Peshawar (Pakistan)
  7. Rawalpindi (Pakistan)
  8. Khoramabad (Iran)
  9. Ahmedabad (India)
  10. Lucknow (India)
  11. Firozabad (India)
  12. Doha (Qatar)
  13. Kanpur (India)
  14. Amritsar (India)
  15. Ludhiana (India)
  16. Igdir (Turkey)
  17. Narayonganj (Bangladesh)
  18. Allahabad (India)
  19. Agra (India)
  20. Khanna (India).

See the Greenpeace India report here

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Photo credit: Getty Images

About Anthony Horton

Anthony holds a PhD in Environmental Science, a Bachelor of Environmental Science with Honours and a Diploma of Carbon Management. In addition to his qualifications, he has a unique ability to explain complex issues in straightforward simple terms. He has a track record of delivering customised solutions in Academia, Government, the Mining Industry and Consulting based on the latest wisdom and his scientific background and experience in Climate/Atmospheric Science and Air Quality. His work has been published in internationally recognised scientific journals and presented at international and national conferences, and he is currently on the Editorial Board of the Journal Nature Environment and Pollution Technology.
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