New Delhi, March 24 India ranks sixth in terms of fine particulate matter pollution, a major air pollutant, while Loni, Uttar Pradesh, is the most polluted city globally, according to the 2025 World Air Quality Report. Delhi is fourth.
The report, compiled by IQAir, a Swiss air quality technology company, analyzed data from monitoring stations across 9,446 cities in 143 countries, regions, and territories.
According to the report, Pakistan is the most polluted country, followed by Bangladesh, Tajikistan, Chad, and Congo, with India in sixth place.
Among the ten most polluted cities globally, five are in India: Loni, Byrnihat, Delhi, Ghaziabad, and Ula.
"The world's 25 most polluted cities are all located in India, Pakistan, and China, with India having three of the four most polluted. Loni, India, is the most polluted city, with an annual average PM2.5 concentration of 112.5 µg/m³, which is nearly 23% higher than in 2024, and more than 22 times the WHO guideline," the report stated.
Comparing this year's report to the previous year, 54 countries experienced an increase in the annual average of PM2.5, 75 saw a decrease, two remained unchanged, and 12 were newly represented in this year's dataset.
"Only 14% of global cities met the World Health Organization (WHO) annual PM2.5 guideline of 5 µg/m³, down from 17% the previous year. Only thirteen countries/territories met the WHO annual average PM2.5 guideline: French Polynesia, Puerto Rico, US Virgin Islands, Barbados, New Caledonia, Iceland, Bermuda, Réunion, Andorra, Australia, Grenada, Panama, Estonia," the report said.
Wildfires, intensified by climate change, played a major role in degrading global air quality in 2025. Record biomass emissions from Europe and Canada contributed to approximately 1,380 megatons of carbon.
Canada was the most polluted country in Northern America for the second time in the report's eight-year history, as its second-worst wildfire season on record affected air quality across Canada, the US, and parts of Europe.
"In the United States, the annual average PM2.5 levels increased to 7.3 µg/m³. Smoke from wildfires in both Canada and the US raised averages across parts of the Great Lakes states in the summer and in the Pacific Northwest in the fall. El Paso was the most polluted major city in the United States. Historic dust storms triggered a 46% increase in PM2.5 levels to 11.4 µg/m³ as the city recorded the highest number of major pre-summer dust storms since the 1930s."
"The Southeast Los Angeles region (Cudahy, East Los Angeles, Huntington Park), heavily impacted by wildland-urban interface fires, ranked as the most polluted area in the country. Seattle remained the cleanest major US city for the second consecutive year, with an annual average of 4.5 µg/m³," the report said.
Across Europe, 23 countries recorded a rise in annual average PM2.5 concentrations, 18 recorded a drop, and one was newly added.
Switzerland and Greece experienced increases exceeding 30% due to transboundary wildfire smoke from Northern America and Saharan dust from Africa. Malta recorded the largest decrease at nearly 24%.
The end of the US State Department’s global air quality monitoring program at embassies and consulates in March 2025 caused millions to lose access to air quality data. Centre for Research on Energy and Clean Air (CREA) reported that monitoring efforts in 44 countries were weakened and six were left without any monitoring.
"Air quality is a fragile asset that requires active stewardship to protect public health. The 2025 World Air Quality Report makes clear that without monitoring, we cannot fully understand what’s in the air we breathe. Expanding access to real-time data empowers communities to act. By reducing emissions and addressing climate change, we can drive meaningful, lasting improvements in global air quality," says IQAir Global CEO Frank Hammes.
The 2025 report underscores the importance of expanding air quality monitoring networks, particularly through low-cost sensors that empower communities, researchers, and policymakers with actionable data.
"The World Air Quality Report reveals two competing realities: an air pollution crisis and the rise of communities, scientists, and data working to meet the challenge. In 2025, familiar culprits like industrial agriculture, wildfires, and fossil fuels left their mark in the data collated by IQAir worldwide," said Aidan Farrow, Senior Scientist, Greenpeace International.
"This open, transparent data is an essential tool for holding polluters accountable and securing a healthy environment for everyone," he said.