Delhi, Kolkata Are World’s Most Polluted Cities by PM 2.5 Exposure: Study

India is home to 18 of the 20 cities with the most severe increase in PM2.5 pollution from 2010 to 2019.

The Quint

Video Producer/Editor: Shohini Bose

In the list of world's most polluted cities, the top two are from India-- Delhi and Kolkata. Mumbai is not far behind with the 14th rank. The people in all three of these cities are exposed to PM2.5 levels that are much higher than the global averages.

India is home to 18 of the 20 cities in the world with the highest rate of increase in PM2.5 levels from 2010 to 2019.

The report, published by Health Effects Institute (HEI) on 17th August, 2022, focuses on two of the most harmful pollutants; fine particulate matter (PM2.5) and nitrogen dioxide (NO2).

Among the most populous cities in each region (N = 103), top 20 with the highest population-weighted annual average PM2.5 exposures in 2019

The Quint

2.6 Billion People Affected by Air Pollution in 2019

The world’s biggest cities and urban areas face some of the worst air quality on the planet.

The report, 'Air Quality and Health in Cities, 2022', gives a detailed analysis of air pollution and global health affects for more than 7,000 cities around the world.

By 2050, almost 68% of the world’s population is expected to live in urban areas, says the report.

Population-weighted annual average PM2.5 concentrations in the five most populous cities in each region in 2019 (N = 103)

Photo: 'Air Quality and Health in Cities, 2022.' Report by HEI

The increased rate of urbanization will lead to the world’s top cities scrambling to reduce the health affects of air pollution, especially in developing countries, found the report.

Fuel burning in older vehicles, power plants, industrial facilities, and residential cooking and heating were identified as the primary reasons for the rising quantity of nitrogen dioxide.

In 2019, 86% of the more than 7,000 cities included in this report exceeded the WHO’s guidelines for NO2, impacting about 2.6 billion people.

While particulate matter pollution tends to get more attention on known hotspots around the world , NO2 is also a major pollutant.

Because city residents tend to live closer to busy roads with dense traffic, they are often at risk of exposure to higher NO2 pollution than residents of rural areas, said the report.

“Since most cities around the world have no ground-based air quality monitoring in place, estimates of particulate and gas pollution levels can be used to plan air quality management approaches that ensure the air is clean and safe to breathe.”

Dr. Susan Anenberg, George Washington University

Air Pollution Responsible for 1 in 9 Deaths 

Breathing even low levels of pollution over time can produce a variety of health effects, including reduced life expectancy, missed school and work, chronic illnesses, and even death, said the report. This puts enormous strains on communities and economies around the world.

Air pollution is responsible for one in nine deaths worldwide, accounting for 6.7 million deaths in 2019, with especially strong impacts on the young, the elderly, and those with chronic respiratory and heart diseases.

Air pollution will continue to pose significant problems, especially in cities with fewer resources due to the rise of urbanisation. But some cities are seeing success as they tackle their pollution problems head on, sai the report.

Need to Improve Air Quality Monitoring Worldwide 

The report also highlights gaps in air pollution data in developing countries.

Only 117 nations currently have ground-level monitoring systems to track particulate matter, and only 74 nations are monitoring nitrogen dioxide levels as mentioned in WHO’s Air Quality Database.

Strategic investments in ground-level air quality monitoring systems and use of satellites and other upcoming technologies in specific regions can prove to be crucial first steps towards cleaner air, the report suggested.

Based on the 2022 WHO Air Quality Database, only two of the 20 cities with the steepest increases in PM2.5 exposures in our data (Patna and Varanasi in India) have an official monitoring station at ground level.

18 of the top 20 cities showing the fastest declines in NO2 exposure over the last decade, are in China.

However, despite these improvements, Beijing still features among the top 20 most polluted cities.

This fact points to the need for improved local air quality monitoring infrastructure worldwide.

Bejing also increased its air monitoring stations from 35 in 2013 to more than 1,000 in 2019, and has seen a 36% drop in the city’s annual particulate matter level in just five years.

Responding to past and continuing high levels of air pollution, Beijing implemented rigorous controls over coal-fired power plants over the past decade. They have also set strict vehicle emission and fuel quality standards to curb traffic-related pollution.

“As cities around the world rapidly grow, the impacts of air pollution on residents’ health are also expected to increase, underscoring the importance of early interventions to reduce exposures and protect public health.”

Pallavi Pant, HEI Senior Scientist