Air Pollution: India's Most Polluted City

India is home to some of the world's most air-polluted cities, with 13 of the top 20 polluted cities globally located in the country. The city of Byrnihat in Assam recorded the worst air pollution in the world in 2024, with a PM2.5 concentration of 128.2 micrograms per cubic meter, over 25 times higher than the World Health Organization's recommended limit. Delhi, the capital of India, is also consistently ranked as one of the most polluted cities, with air pollution worsening in winter due to various factors. Indian cities' severe air pollution results from a combination of industrial emissions, vehicle exhaust, and reliance on fossil fuels, exacerbated by weak regulations and seasonal weather patterns.

Delhi: the most polluted city in India

Delhi is the most polluted city in India, according to a report published in March 2025. The World Air Quality Report 2024 by Swiss air quality company IQAir ranked Delhi as the most polluted capital city in the world. The report also stated that India was the fifth most polluted country in the world in 2024, with 13 of the world's top 20 polluted cities.

Delhi's poor air quality is a persistent issue, exacerbated by a combination of factors. Vehicular emissions, paddy straw burning, firecrackers, and other local pollution sources contribute to the hazardous air quality, particularly during the winter months when meteorological conditions are unfavourable. The annual average PM2.5 concentration in Delhi increased from 102.4 micrograms per cubic metre in 2023 to 108.3 micrograms per cubic metre in 2024, far surpassing the World Health Organization's recommended limit of 5 micrograms per cubic metre.

The high levels of air pollution in Delhi have severe health implications for its residents. A Lancet Planetary Health study estimated that approximately 1.5 million deaths in India annually, from 2009 to 2019, were potentially linked to long-term exposure to PM2.5 pollution. The report also found that air pollution reduced life expectancy in India by an estimated 5.2 years.

To address the air pollution crisis in Delhi, experts have suggested a range of solutions. These include transitioning from biomass to LPG, expanding public transportation, imposing fines on certain cars, providing subsidies for electric vehicles, and strictly enforcing emission laws for industries and construction sites. Implementing these measures is crucial to improving air quality and safeguarding the health of Delhi's residents.

While Delhi holds the unfortunate distinction of being India's most polluted city, it is important to note that other Indian cities also struggle with severe air pollution due to industrial emissions, vehicle exhaust, and reliance on fossil fuels, underscoring the urgent need for comprehensive measures to tackle this public health challenge.

Byrnihat, Assam: worst air pollution globally in 2024

India is home to some of the world's most air-polluted cities, with 11 out of the top 20 cities in 2024. Byrnihat, a city in northeastern India, recorded the worst air pollution globally in 2024, with a PM2.5 concentration of 128.2 micrograms per cubic meter—over 25 times higher than the World Health Organization's recommended limit of 5 micrograms per cubic meter.

Byrnihat is located on the Meghalaya-Assam border, around 20 km from Guwahati and 65 km from Shillong. It has developed into a regional industrial hub, with industries in both Meghalaya and Assam, including those involved in the production of coke, cement, ferro alloys, and steel, as well as distillation and brickmaking. The proximity to coal reserves in Meghalaya and the large urban centre of Guwahati, as well as the supply of water from the Umtru river, have contributed to the growth of industries in the area.

The poor air quality in Byrnihat has been attributed to industrial activities, vehicular emissions, and the non-use of pollution control devices. The Assam Pollution Control Board has served notices to several industries for violating pollution norms, including heavy emissions and non-compliance with tailpipe emission standards. Meghalaya Chief Minister Conrad Sangma acknowledged that the major sources of air pollution may be attributed to industrial activities on the Assam side, with 20 "red category" industries identified as heavily polluting, compared to five in Meghalaya.

To address the air pollution issue in Byrnihat, the Meghalaya state government released the Meghalaya State Action Plan for Prevention and Control of Air Pollution in December 2024. The plan identified 39 industrial units in Assam and 41 in Meghalaya as contributing to the poor air quality in the area. The MSPCB has also engaged the CSIR-NEERI to conduct an emission inventory and source apportionment study of Byrnihat.

Industrial emissions, vehicle exhaust, and fossil fuels

India is home to some of the world's most air-polluted cities, with Byrnihat, a city in northeastern India, recording the worst air pollution globally in 2024. The country's air pollution can be attributed to a mix of industrial emissions, vehicle exhaust, and fossil fuels, which are worsened by weak regulations and seasonal weather patterns.

Industrial Emissions

Industrial emissions are a significant contributor to India's air pollution. The burning of fossil fuels, such as coal, crude oil, and natural gas, in industries has been a major source of pollution, posing health hazards to the population. The combustion of these fuels releases pollutants such as carbon dioxide (CO2), sulphur dioxide (SO2), and nitrogen oxides (NOx), which have adverse health effects, including cardiovascular and respiratory diseases, chronic bronchitis, and increased morbidity. Industrial emissions also encompass power plant emissions, contributing to the formation of ground-level ambient ozone when reacting with hydrocarbons in the presence of sunlight.

Vehicle Exhaust

Vehicle exhaust emissions play a crucial role in India's air pollution crisis. The country's transportation sector, including taxis, auto-rickshaws, trucks, and private vehicles, contributes significantly to the pollution levels. Adulterated fuel blends, common in Indian vehicles, increase emissions of harmful pollutants. For example, the addition of kerosene results in higher levels of hydrocarbons (HC), carbon monoxide (CO), and particulate matter (PM) emissions, even from catalyst-equipped cars. Traffic congestion in Indian cities exacerbates the problem, as vehicles burn fuel inefficiently and pollute more per trip at low speeds. The increasing number of vehicles and slow traffic speeds lead to a buildup of local pollution, particularly under stagnant conditions.

Fossil Fuels

The combustion of fossil fuels is a primary source of air pollution in India. The use of coal, crude oil, and natural gas for energy generation and commercial electricity consumption contributes significantly to ambient particulate matter pollution. Residential emissions from cooking and heating with polluting fuels, such as solid fuels like wood, dung, agricultural residues, coal, and charcoal, also play a role in household air pollution. Efforts to transition to cleaner fuels, such as liquefied petroleum gas (LPG) and compressed natural gas (CNG), have shown positive results in reducing Sulphur dioxide (SO2) and nitrogen dioxide (NO2) levels in some cities. Additionally, the Indian government has implemented measures to reduce the use of solid fuels for cooking and promote the adoption of electric vehicles to improve air quality.

Weak regulation and seasonal weather patterns

India is home to some of the world's most air-polluted cities, with Byrnihat, a city in northeastern India, recording the worst air pollution globally in 2024. The country's air pollution crisis is a result of a mix of industrial emissions, vehicle exhaust, and reliance on fossil fuels, all exacerbated by weak regulations and seasonal weather patterns.

India's air quality is significantly influenced by geographical variability and seasonal weather patterns. Key pollutants such as particulate matter (PM), oxides of nitrogen (NOx), ammonia (NH3), sulphur dioxide (SO2), and non-methane volatile organic compounds (NMVOCs) are predominantly emitted from transport, industrial processes, farming, energy generation, and domestic fuel use for cooking and heating. Pollution levels in India are often much higher than the World Health Organization's recommended levels, particularly during the winter season in cities and the harvesting period in rural areas of the northern Indian states.

Weak regulations and limited monitoring of pollution data further compound the issue. India's monitor density of 0.25 per million population is the lowest among big countries, with only 5 monitoring stations in Delhi, a city of over 16 million people. While the Indian government has launched initiatives like the National Clean Air Program (NCAP) in 2019 to reduce PM concentrations, the enforcement of environmental regulations remains lax. Atmospheric stagnation, which worsens PM2.5 pollution, is expected to increase in India due to climate change, leading to more winter stagnation days and worsening air quality.

Seasonal weather patterns also play a significant role in India's air pollution crisis. The fall months experience increased emissions from post-harvest agricultural residue burning and the onset of western disturbances, leading to slower pollution movement and the formation of secondary particulates. Burning agricultural residue and forest fires are observed across India, but their impact is most significant in Punjab, Haryana, and Delhi. The spring months bring sporadic dust storms from the west, while the monsoon months bring substantial rains that help clear the air of pollutants.

To address the complex issue of air pollution in India, a multi-faceted approach is necessary, including stricter enforcement of environmental regulations, investment in clean technologies, sustainable urban planning, and public participation in pollution control efforts.

Air pollution: a serious health risk in India

Air pollution is a critical public health threat in India, causing millions of premature deaths and diseases annually. In 2016, outdoor air pollution alone was responsible for an estimated 1,795,181 deaths in the country from stroke, heart disease, lung cancer, and chronic respiratory diseases. The situation has only worsened in recent years, with India accounting for 11 of the top 20 most air-polluted cities in the world in 2024. Byrnihat, a city in northeastern India, recorded the worst air pollution globally in 2024, with a PM2.5 concentration of 128.2 µg/m³—exceeding the World Health Organization's recommended limit by over 25 times.

India's air pollution crisis is driven by a combination of industrial emissions, vehicle exhaust, and a reliance on fossil fuels, exacerbated by weak regulations and seasonal weather patterns. In rural areas, biomass burning for cooking and heating contributes significantly to the problem. Fuelwood and biomass cakes, burned in traditional cookstoves, create a near-permanent haze and smoke observed over both rural and urban India. This practice alone is estimated to cause 300,000 to 400,000 deaths annually due to indoor air pollution and carbon monoxide poisoning.

The health consequences of air pollution are dire, leading to respiratory and cardiovascular diseases, including asthma, bronchitis, COPD, lung cancer, and heart attacks. The impact is felt disproportionately by women, newborns, and young children. Additionally, air pollution adversely affects economic productivity, with an estimated loss of US$28.8 billion in output in 2019 due to worsening air pollution.

Recognizing the severity of the issue, the Indian government has implemented policies such as the National Clean Air Programme and the Pradhan Mantri Ujjwala Yojna to improve access to clean energy options and reduce ambient air pollution. However, the challenge remains immense, and continued efforts are necessary to address this pressing health risk.

The COVID-19 lockdown period in India provided an interesting insight into the potential for air pollution reduction. With reduced human activity, air quality across the country improved significantly. This improvement underscores the impact of human activities on air pollution levels and the potential for positive change through policy interventions and behavioral modifications.

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