World’s Most Polluted City
The World Health Organization studied the air quality of 1,600 cities in 91 countries in 2014. Delhi was ranked at number 1 as the most polluted city in the world. Beyond the findings for Delhi, 13 of the 20 cities found to have the highest annual averages of PM2.5 in the WHO study were Indian cities.
Using satellite-based remote sensing technology and ground level data from the Central Pollution Control Board, Dr. Michael Greenstone and his team produced an influential study (Greenstone et al, 2015) showing that 660 million people (more than half of India’s population) lived in areas that exceed India’s standards for fine particulate pollution. Large portions of India, in particular in the north along the Indo-Gangetic Plain can been seen to be heavily polluted and in non-compliance with India’s National Air Quality Standards (NAAQS.)
Since 2014, this data has been updated by the W.H.O. and though New Delhi got displaced from the top of the list, it wasn’t due to actions taken to clean its air, but because W.H.O started tracking other more polluted cities in the world. In November 2016, Delhi’s air was actually the worst it had been in the past 17 years, forcing the Indian government to declare an “emergency situation” and temporarily closed schools, construction sites, and power stations until the pollution came under control. As per the World Air Quality Report prepared by IQAir, Delhi ranked fourth on a list of 50 of the world’s most polluted cities in terms of PM2.5 levels in 2022. Delhi had an average PM2.5 level of 92.6 ug/m3. The WHO guideline for annual PM2.5 levels is 5ug/m3. Over the past four years Delhi has topped the IQAir list of most polluted capital cities. In 2022, Delhi’s average PM2.5 level was the highest in November. (IQAir is a Swiss air quality technology company that prepares annual world air quality reports based on data from monitoring stations operated by governments and other institutions across the world. The 2022 report is based on PM2.5 data from 7323 cities and 131 countries).
Air pollution in Delhi’s National Capital Region (NCR) is comprised of a complex mix of pollution from human activities (vehicle emissions, industry, construction and residential fuel burning) as well as natural sources like dust. The heavy concentration of particulate matter is greatly affected by meteorological conditions –in the winter, cold air causes “inversions” that stagnate the air and trap pollution close to the ground. Air flow patterns from Afghanistan and Pakistan collect emissions as they move over the densely urbanized regions of Punjab and Haryana where farmers burn the straw in their fields, and pull this pollution into Delhi. Pre-monsoon dust storms also contribute to air pollution in the region.
City activities contribute immensely to the air pollution. The Delhi NCR generates more than 11,300 tons per day of municipal solid waste, much of which is eventually burned, adding particulate pollution to the air. Rapid urbanization results in massive construction projects which add to the dust and particulate pollution. In addition, Delhi has more than 13.4 million vehicles on its roads, with an additional 1,700 added each day, resulting is a pollution “hotspot.”.
Over the last decade air pollution in Delhi has been worsening. In Delhi, particulate matter pollution, the component of pollution more harmful to health, is usually worst in the winter. Stubble burning and Diwali fireworks in the winter season bring a substantial increase in pollution numbers during the cold weather. Ground level ozone, however, peaks in June. Day by day, pollution levels often peak around midnight.
Efforts to mitigate air pollution in Delhi began long ago, to varying short-term success but no long-term effective strategy has been identified or adopted. A new wave of policies is currently in the process of being discussed.
Using satellite-based remote sensing technology and ground level data from the Central Pollution Control Board, Dr. Michael Greenstone and his team produced an influential study (Greenstone et al, 2015) showing that 660 million people (more than half of India’s population) lived in areas that exceed India’s standards for fine particulate pollution. Large portions of India, in particular in the north along the Indo-Gangetic Plain can been seen to be heavily polluted and in non-compliance with India’s National Air Quality Standards (NAAQS.)
Since 2014, this data has been updated by the W.H.O. and though New Delhi got displaced from the top of the list, it wasn’t due to actions taken to clean its air, but because W.H.O started tracking other more polluted cities in the world. In November 2016, Delhi’s air was actually the worst it had been in the past 17 years, forcing the Indian government to declare an “emergency situation” and temporarily closed schools, construction sites, and power stations until the pollution came under control. As per the World Air Quality Report prepared by IQAir, Delhi ranked fourth on a list of 50 of the world’s most polluted cities in terms of PM2.5 levels in 2022. Delhi had an average PM2.5 level of 92.6 ug/m3. The WHO guideline for annual PM2.5 levels is 5ug/m3. Over the past four years Delhi has topped the IQAir list of most polluted capital cities. In 2022, Delhi’s average PM2.5 level was the highest in November. (IQAir is a Swiss air quality technology company that prepares annual world air quality reports based on data from monitoring stations operated by governments and other institutions across the world. The 2022 report is based on PM2.5 data from 7323 cities and 131 countries).
Air pollution in Delhi’s National Capital Region (NCR) is comprised of a complex mix of pollution from human activities (vehicle emissions, industry, construction and residential fuel burning) as well as natural sources like dust. The heavy concentration of particulate matter is greatly affected by meteorological conditions –in the winter, cold air causes “inversions” that stagnate the air and trap pollution close to the ground. Air flow patterns from Afghanistan and Pakistan collect emissions as they move over the densely urbanized regions of Punjab and Haryana where farmers burn the straw in their fields, and pull this pollution into Delhi. Pre-monsoon dust storms also contribute to air pollution in the region.
City activities contribute immensely to the air pollution. The Delhi NCR generates more than 11,300 tons per day of municipal solid waste, much of which is eventually burned, adding particulate pollution to the air. Rapid urbanization results in massive construction projects which add to the dust and particulate pollution. In addition, Delhi has more than 13.4 million vehicles on its roads, with an additional 1,700 added each day, resulting is a pollution “hotspot.”.
Over the last decade air pollution in Delhi has been worsening. In Delhi, particulate matter pollution, the component of pollution more harmful to health, is usually worst in the winter. Stubble burning and Diwali fireworks in the winter season bring a substantial increase in pollution numbers during the cold weather. Ground level ozone, however, peaks in June. Day by day, pollution levels often peak around midnight.
Efforts to mitigate air pollution in Delhi began long ago, to varying short-term success but no long-term effective strategy has been identified or adopted. A new wave of policies is currently in the process of being discussed.
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