Bengaluru: India is the sixth most-polluted country when it comes to levels of fine particulate matter, a major air pollutant, as per the 2025 World Air Quality Report by IQAIR, a Swiss air quality technology company.Weighted by population, India’s average concentration of fine particulate matter (PM2.5) measured in micrograms per cubic meter (µg/m³), in 2025 was 48.9 (it was 50.6 in 2024). The World Health Organisation’s (WHO’s) recommended annual guideline level is 5 µg/m³. This small decline in PM2.5 levels, however, is not “statistically significant”, the lead author of the report told The Wire.India is still home to the most polluted city in the world: in 2025, it was Loni in Ghaziabad, recording an annual average PM2.5 concentration of 112.5 µg/m³, which is more than 22 times the WHO permissible guidelines. Among capital cities across the world, India’s New Delhi ranked as the most polluted capital, with an average PM2.5 concentration of 82.2 µg/m³.Global trends: India home to most polluted cityThe 2025 IQAir World Air Quality Report provides data on concentration of fine particulate matter (PM2.5) across the world. The data is sourced from 9,446 cities spanning 143 countries, regions, and territories (when compared to 8,954 cities in 138 nations last year) and from more than 40,000 regulatory monitoring stations and low-cost sensors, managed by government agencies, universities, non-profit organisations, private enterprises and citizen scientists. Globally, only 13 countries, regions and territories saw annual average PM2.5 concentrations meeting the WHO annual PM2.5 guideline of 5 μg/m³, with the majority located in the Latin America and Caribbean region. According to the report, Central and South Asia continue to experience the highest annual average PM2.5 concentrations globally, with 17 of the world’s 20 most polluted cities in 2025 being located in this region. “Of the 358 cities across 10 regional countries included in the 2025 Report, 71 cities reported annual average concentrations exceeding 50 µg/m³, more than ten times the current WHO guideline,” the report noted. Loni in Ghaziabad in India was the most polluted city, recording an annual average PM2.5 concentration of 112.5 µg/m³ – a nearly 23% increase from 2024 and more than 22 times the WHO guideline, per the report. The cleanest city, meanwhile, was Nieuwoudtville in South Africa, with an annual average PM2.5 concentration of just 1.0 µg/m³.Compared to last year, 54 countries experienced increases in annual average PM2.5, 75 saw declines, two remained unchanged and 12 were newly represented in this year’s dataset, the report said.“Air quality is a fragile asset that requires active stewardship to protect public health,” IQAir Global CEO Frank Hammes said in a statement. “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.”India, sixth most polluted in 2025Pakistan was the most-polluted country in terms of average PM2.5 levels in 2025. The country had the highest population-weighted average PM2.5 concentration for the year, at 67.3 μg/m³. India came at sixth place at 48.9 μg/m³, after Bangladesh (66.1 μg/m³), Tajikistan (57.3 μg/m³), Chad (53.6μg/m³) and the Democratic Republic of Congo (50.2 μg/m³). Among capital cities across the world, New Delhi ranked as the most polluted capital, with an average PM2.5 concentration of 82.2 µg/m³ in 2025. Delhi was followed by Dhaka (Bangladesh) and Dushanbe (Tajikistan) at 68 and 57.3 µg/m³ respectively. “Major capital cities such as Dushanbe, Dhaka, and Delhi faced particularly extreme conditions in 2025, with each city recording at least two months where concentrations surged above 100 µg/m³. Given the high population density in these urban centers, these sustained pollution levels represent a constant and significant threat to public health,” the report noted. The world’s 25 most polluted cities were all located in India, Pakistan and China, with India home to three of the four most polluted, it noted.Source: IQAir World Air Quality Report, 2025While Loni was the most polluted city in the world in 2025, Byrnihat in Meghalaya (which was the world’s most polluted city as per the 2024 IQAIR report with an annual PM2.5 concentration of 128.2 µg/m³) came third, recording a PM2.5 concentration of 101.1 µg/m³.Fourth came Delhi, at 99.6 µg/m³, per the 2025 report. Seventh came Ghaziabad at 89.2 µg/m³, and tenth came the city of Ula or Birnagar in West Bengal, with an annual PM2.5 concentration of 86.6 µg/m³.Small decline in India’s PM2.5 levels not ‘statistically significant’Overall, in 2025, India’s national average PM2.5 levels saw a 3% decline, dropping from 50.6 µg/m³ in 2024 to 48.9 µg/m³, per the report. However, this change is not statistically significant, Christi Chester Schroeder, IQAir’s lead air quality scientist and the report’s lead author, told The Wire. “Such changes can be attributed to weather patterns such as wind or rain, and likely not due to permanent changes. Throughout Southeast Asian countries (Thailand, Indonesia, Vietnam, etc.), La Nina conditions eased air pollution concentrations due to wind, rain, and higher typhoon activity. Some parts of India likely saw some of these effects as well, but there is still a way to go before meaningful progress is being made in India in regard to air pollution,” she said.And while Delhi’s annual average concentration fell by 8%, the city still grappled with severe monthly spikes driven by seasonal smog and dust storms, per the report.“Specifically, a massive dust storm in April caused Delhi’s PM2.5 levels to surge by 15% that month. In December, PM2.5 averages spiked by 44% in Delhi and by an average of 62% in neighboring cities across Uttar Pradesh. Among these, the city of Loni in the Ghaziabad district emerged as India’s most polluted city in 2025; its annual average concentration climbed nearly 23% to 112.5 µg/m³, following extreme pollution events in March, April, and December,” the report said.Need better enforcementVehicular emissions, industrial emissions, crop residue burning and construction dust remained the dominant sources of fine particulate matter pollution in the country.“Despite the National Clean Air Programme’s goal to reduce pollution by 40% by 2025-2026, 64% of funding has been dedicated to road dust reduction; only 15% of funding has been used to reduce biomass burning, 13% for vehicle emissions, and only 1% to counter industrial pollution,” the report noted. The Programme’s focus on reducing only PM10 concentrations, rather than the more harmful PM2.5, is also a concern, it added. It also highlighted that “weak enforcement of vehicular and industrial emission norms, combined with relaxed sulfur rules for coal plants, likely impacted air quality”.In July last year, the Union environment ministry exempted nearly 80% of thermal power units across the country from installing technology to limit sulphur emissions called flue-gas desulphurisation systems. Air pollution scientists had then told The Wire that this ‘takes India back 10 years’, as FGDs are the only way to control sulphur emissions from power plants and thus, reduce pollution at the source. They had added that the rationale for the move – such as India witnessing a lack of technology to implement FGD systems – was “absurd”. “Industrial sources require stricter enforcement and continuous emissions monitoring, particularly among small and medium enterprises. Construction and road dust, often overlooked, remain significant contributors and demand better regulation and urban planning. Expanding real-time air quality monitoring can help identify hotspots and improve accountability. Introducing renewable energy sources such as wind and solar power are essential in reducing India’s heavy reliance on fossil fuels. Ultimately, the challenge is less about identifying solutions and more about implementing them consistently and at scale across jurisdictions,” said Schroeder.While India maintains the overall region’s most robust monitoring network – followed by Pakistan and Kazakhstan – the data reveals a consistent regional pattern of elevated concentrations, Schroeder added. “India’s persistent regional air pollution patterns point to systemic sources that require coordinated, multi-state action rather than isolated city-level fixes. While frameworks like the National Clean Air Programme exist, stronger alignment across states, particularly in the Indo-Gangetic Plain, is critical to drive meaningful reductions,” she said. India needs to address consistent issuesIndia’s main focus in order to reduce PM2.5 should start in three main areas: reducing the use of dirty fuels for vehicles, relying less on fossil fuels for energy, and reducing seasonal crop burning, Schroeder told The Wire. “These three areas have been and remain consistent issues throughout India. Coal represents almost half of the country’s total energy supply and three-quarters of electricity generation. While India is expanding renewable energy capacity, fossil fuel use still makes up a vast majority of the country’s energy needs.”Key interventions include curbing agricultural burning through financial incentives and viable alternatives for farmers, and accelerating the transition away from coal by retrofitting or retiring the most polluting plants. Transport emissions must also be addressed at scale through tighter standards, expanded public transit, and rapid electrification, Schroeder added.India also has an estimated 400+ million vehicles and the world’s third largest road network. Vehicle engine combustion in those numbers greatly contribute to significantly elevated air pollution levels. “It is even more so affected in hotter months, when PM2.5 from vehicles and heat undergo a chemical reaction to generate ozone pollution, known as smog. While the 2025 World Air Quality Report doesn’t focus on ozone specifically, we do see elevated levels of ozone in hotter months,” she said.Ozone pollution has been an emerging issue across the country. In September last year, the National Green Tribunal (NGT), India’s apex green court, took suo motu cognisance of a rise in ground-level ozone pollution across several Indian cities. Asked for a response on this, the Central Pollution Control Board had told the NGT that the National Capital Region is the worst impacted in the country by high levels of ground-level ozone pollution, followed by the Mumbai Metropolitan Region (MMR). Chemical reactions between nitrogen oxides and volatile organic compounds emitted by vehicles, industries and thermal power plants were the main causes of air pollution in Mumbai last winter, the CPCB had also said.