Hong Kong – Six of the world’s 10 most polluted cities are in India, but California has the worst air pollution in North America, a new report shows.
New Delhi is the world’s most polluted capital, followed by N’Djamena, the capital of Chad, a central African country with the worst air pollution in the world, according to a 2024 World Air Quality Report published by Swiss air monitoring company IQAIR.
Of the 15 most polluted cities in North America, including Ontario and Bloomington, 10 are located in California as the US regained its top position as the region’s most polluted country in 2024, the report says.
India, the world’s most populous country with over 1.4 billion people, saw a 7% drop in PM2.5 concentration in 2024, but air pollution estimates the average life expectancy of South Asian countries by 5, and remains a “significant health burden” that reduces the average life expectancy by 2 years. The country’s major sources of pollution include industrial emissions, construction dust and the combustion of crop residues.
PM2.5 refers to small particles with a diameter of less than 2.5 micrometers, allowing them to go deep into the lungs and even enter the bloodstream. It is associated with early death, heart attacks and difficulty breathing, as it comes from sources of emissions such as gasoline and oil burning.
Chad’s PM2.5 levels were more than 18 times higher than WHO guidelines, with Sahara Desert mineral dust being the main source of air pollutants. Oceania, including Australia, New Zealand and Pacific Island countries, is the cleanest region in the world, with 57% of cities meeting WHO standards.
Bangladesh and Pakistan both ranked neighboring India as the second and third most polluted countries. Last November, Pakistan’s air quality reached a “dangerous” level due to a combination of festival celebrations, brick-style emissions and bad weather.
Focusing on the “ambitious” target of Chinese authorities at a national average annual PM2.5 concentration level below 25 micrograms per cubic meter, the report says it will “significantly” surpass the WHO guidelines of 5 micrograms.
Chinese environmental officials said last month that China aims to effectively eliminate severe air pollution by the end of this year. China announced the “War on Pollution” in 2014.
The report also noted the “substantial” gap in air quality that is still present in many parts of the world. Currently, only 21% of the world’s population can access hyperlocal real-time air quality information, according to IQAIR estimates.
Cambodia had no official government surveillance, but many important regions of Africa and West Asia lacked sufficient surveillance. In comparison, North America has a “robust” air quality monitoring infrastructure that accounts for 56% of ground-based stations. “Air pollution remains an important threat to both human health and environmental stability, but the vast population remains unaware of exposure levels.
“Air quality data saves lives,” Hamms said. “It generates a lot of necessary awareness, informs policy decisions, guides public health interventions, and enables communities to take action to reduce air pollution and protect future generations.”
Last week, the US embassy and consulate said it had stopped monitoring air quality overseas and ended a program that had been providing critical public health data for more than a decade.
Data provided by the US, provided in dozens of countries, has led to significant improvements in local air quality in China and elsewhere, reducing early deaths and creating cost reductions associated with lower mortality, studies have found.
According to the WHO, air pollution accounted for 8.1 million deaths worldwide in 2021. Children under the age of 5 are considered particularly vulnerable and have health effects such as preterm birth, low birth weight, asthma and lung disease.
