India's Top 5 Most Polluted Cities and Their Air Quality Levels

Air pollution is a big problem in India, affecting millions of people every day. Many cities struggle with poor air quality, leading to health issues and making daily life harder. But which cities are the worst affected? In this blog, we’ll explore India’s top 5 most polluted cities and their air quality levels.

These cities often have very high Air Quality Index (AQI) levels, which means the air is not safe to breathe. Pollution from factories, vehicles, and construction work makes the air even worse. It doesn’t discriminate by age, everyone is affected. Studies show that exposure to air pollution while in the womb is linked to adverse changes in cell processes in new-born babies, which can lead to long-term health risks. Even though efforts are being made to improve the situation, the fight for good and healthy air is still ongoing.

Knowing which cities are most polluted and why can help us take steps to improve air quality. Whether you live in these cities or are just curious, this blog will give you useful insights into India’s pollution problem and what’s being done to fix it. Let’s take a closer look at these pollution hotspots.

The 5 Most Polluted Cities in India

Air pollution continues to be a critical environmental and public health challenge in India, with several cities consistently ranking among the most polluted in the world. But what defines a polluted city, and why do some regions struggle more than others? Let’s delve into the metrics, current rankings, and future trends to understand this better.

Key Metrics of Air Pollution

Air pollution levels are determined using the Air Quality Index (AQI), which measures pollutants such as:

PM2.5 & PM10: Fine and coarse particulate matter causing respiratory and cardiovascular diseases.
NO2 (Nitrogen Dioxide): Primarily from vehicular emissions and industrial processes.
SO2 (Sulfur Dioxide): A byproduct of fossil fuel combustion.
CO (Carbon Monoxide): Emitted from vehicular and industrial sources.
O3 (Ozone): Formed by chemical reactions in the atmosphere under sunlight.

India’s Top 5 Most Polluted Cities

Based on recent air quality data collected on 23/01/25 at 11:30 AM, the following cities consistently experience hazardous pollution levels:

Delhi - 224 AQI, which is considered to be very unhealthy or poor
Kolkata - 174 AQI, which is considered to be unhealthy or moderately polluted
Ghaziabad - 168 AQI, which is considered to be unhealthy or moderately polluted
Greater Noida - 165 AQI, which is considered to be unhealthy or moderately polluted
Mumbai - 138 AQI, which is considered to be unhealthy for sensitive groups or moderately polluted.

Delhi – The Smog Capital of India - 224 AQI

There was a time when people could breathe clean air without worrying about harmful pollutants like sulfur dioxide, carbon monoxide, ground-level ozone, PM2.5, or PM10. But today, smog is everywhere. Have you ever wondered what smog is and how it forms? Let’s find out.

The term "smog" combines the words smoke and fog and was first used in the 1900s when coal burning in industrial areas was a major cause. Over time, pollution sources have evolved. Today, smog is not just from factories; it also includes photochemical smog, which forms when nitrogen oxides (NOX) and volatile organic compounds (VOCs) react with sunlight. NOX comes from vehicle exhausts and coal-burning plants, while VOCs are released from petrol, cleaning products, and paints. When these pollutants mix with sunlight, they create ground-level ozone and smog.

Major Causes of Delhi’s Air Pollution:

Crop Burning in Neighboring States: Farmers in Punjab, Haryana, and Uttar Pradesh burn crop stubble post-harvest, releasing large amounts of smoke and harmful particles. Winds carry these pollutants into Delhi, worsening the city's air quality.
Stagnant Winter Air: During winter, Delhi experiences cold and still air conditions. This traps pollutants like smoke and dust near the ground, leading to the accumulation of smog and increased health risks.
Overpopulation: With over 20 million residents, Delhi's rapid urban growth strains infrastructure. More people result in increased vehicle usage, waste generation, and energy consumption, all contributing to higher pollution levels.
Traffic Congestion: The city's roads are crowded with vehicles, many of which are older models emitting high levels of harmful gases. Limited public transport options force reliance on private cars, leading to constant traffic jams and elevated air pollution.
Fireworks During Festivals: Despite bans, fireworks are commonly used during festivals like Diwali. These release harmful chemicals, including sulfur dioxide and particulate matter, exacerbating pollution during festive seasons.
Construction Dust: Ongoing construction projects generate significant dust, especially during dry weather. This contributes to particulate matter in the air, further degrading air quality

Did you know this? A study by the Centre for Science and Environment reveals that during the period of October 12 - November 3, 2024, vehicular emissions are the largest contributor to Delhi’s air pollution, accounting for 51.5 percent of the city’s pollution.

Experts say rain can help reduce pollution by settling dust, but its impact depends on the intensity. While heavy rain can bring significant improvement, light showers provide only short-term relief.

Kolkata – Alarming Air Quality Statistics - 174 AQI

Delhi's air pollution recently made headlines when the Air Quality Index (AQI) soared to 700 in some areas. Schools were closed, and masks, once used during the COVID-19 pandemic, became a common sight again. Air pollution was widely discussed, but as the AQI dropped below 250 (still considered ‘very unhealthy’), the urgency faded, and life returned to normal. This raises important questions: Are we ignoring a bigger crisis? Are other cities safe from this growing environmental challenge?

Delhi’s air pollution is a widely discussed global issue, with various efforts aimed at reducing its smog. However, other Indian cities facing similar or worse pollution levels often don't receive the same attention. Kolkata, a metro city with over 14 million people, has been struggling with severe air pollution in recent years.

Kolkata, another major city, is experiencing a steady rise in pollution levels. Although it hasn't reached Delhi’s extreme levels yet, its AQI, ranging between 150-200, is already in the ‘unhealthy’ category. If pollution control measures aren't taken seriously, Kolkata could face a similar crisis in the coming years.

Ignoring the problem now may lead to severe consequences, making it crucial for authorities and citizens to act before it’s too late.

Kolkata's air pollution is rising due to multiple factors. Seasonal wind patterns bring pollutants from neighboring regions, making up a significant portion of the city's pollution load. Vehicular emissions, coal combustion, and industrial discharges further degrade air quality, especially during winter when cold air traps pollutants. Additional sources include construction dust, waste burning, and the widespread use of coal for cooking in roadside stalls and slums. Lack of strict regulations and enforcement also contributes to worsening air conditions.

Ghaziabad - AQI 168

The Indian state of Uttar Pradesh contains the city of Ghaziabad. It is sometimes called the "Gateway of UP" due to its proximity to New Delhi and its location on the main highway into Uttar Pradesh. It is a component of Delhi's National Capital Region. It is a sizable, strategically located industrial city.

Ghaziabad, a city in Uttar Pradesh, India, faces significant air pollution challenges due to various sources:

Vehicular Emissions: The increasing number of vehicles contributes to high levels of nitrogen dioxide (NO2) and particulate matter (PM). As of January 21, 2025, the NO2 level was recorded at 27 (ppb), which is 2.03 times above the World Health Organization's recommended guideline of 13.29 ppb.
Industrial Activities: Numerous industries release pollutants into the air, elevating concentrations of PM2.5 and PM10. On January 21, 2025, the PM2.5 level reached 85 micrograms per cubic meter (µg/m³), and PM10 was at 180 µg/m³, both indicating unhealthy air quality.
Construction Dust: Ongoing construction projects generate dust particles, further increasing PM levels. This contributes to the city's Air Quality Index (AQI) reaching 172, categorized as unhealthy.
Burning of Waste: Open burning of garbage and agricultural residue releases harmful pollutants, exacerbating air quality issues.

Greater Noida - AQI 165

According to the CPCB date, on Thursday, 23rd Feb 2025, the AQI in Greater Noida was 165, in the “unhealthy” category.

Greater Noida, a rapidly growing urban and industrial hub, faces severe air pollution due to several key factors. Industrial emissions from factories and power plants release pollutants like particulate matter (PM), sulfur dioxide (SO2), and nitrogen oxides (NOX) into the air. Vehicular emissions from the rising number of cars and trucks contribute significantly to air pollution, emitting carbon monoxide (CO), PM, and volatile organic compounds (VOCs).

Construction dust from ongoing infrastructure projects adds to the pollution levels, releasing fine particulate matter (PM2.5 and PM10) that impacts air quality. Additionally, stubble burning in neighboring regions, especially during winter, worsens air pollution by introducing smoke and harmful particles into the atmosphere. Waste burning and inadequate waste management practices further contribute to toxic emissions.

The region’s geography and weather conditions, such as temperature inversions and low wind speeds, trap pollutants, leading to prolonged exposure. Tackling Greater Noida’s air pollution requires stringent policies, better enforcement of regulations, and increased public awareness to reduce emissions and promote sustainable practices.

Mumbai: Financial capital of India - AQI 138

Mumbai's air quality improved in 2024, nearing pre-pandemic levels, but experts caution that 'moderate' AQI is still far from healthy standards. However, The hazy skyline of Mumbai has always been a clear sign of the city's ongoing air pollution problems. Construction activities, especially big housing projects and infrastructure work, have increased pollution levels. The cold weather makes it worse by keeping tiny dust particles in the air for longer, stopping them from spreading out.

Mumbai, a renowned financial capital of India on the west coast, grapples with significant air pollution challenges. The primary cause is dust from construction activities. These sources release fine particulate matter (PM2.5) into the atmosphere, posing health risks.

Contributing factors to Mumbai air pollution include vehicular emissions, industrial emissions construction, and road dust. Addressing these issues requires comprehensive strategies, including enhancing public transportation, enforcing stricter industrial regulations, and promoting sustainable agricultural practices.

Health Impacts of Air Pollution

Air pollution affects our health in many ways, both indoors and outdoors.

Breathing Problems: Pollutants like PM2.5 and nitrogen oxides can cause asthma, bronchitis, and other lung issues. Symptoms range from coughing and throat irritation to severe breathing difficulties.
Heart Issues: Pollution doesn’t just affect the lungs; it can harm the heart, too. It can lead to high blood pressure, heart attacks, and inflammation.
Brain Effects: Air pollution can impact brain health, leading to memory loss and cognitive decline, especially in children and older adults. It’s even linked to dementia, making it crucial to improve air quality for better health.

Were you aware of this? Long-term exposure to air pollution may worsen menopause symptoms. A recent study found that poor air quality affects health beyond just breathing problems, highlighting its impact throughout life.

Steps to Reduce Air Pollution in India

Improving air quality needs strong policies, smart technology, and cleaner energy. Using electric vehicles, better waste management and renewable energy can cut pollution. Raising awareness and promoting sustainable habits help everyone play a part in making the air cleaner.

Key Solutions:

Government Policies: Programs like the National Clean Air Programme (NCAP) set emission targets and stricter rules to reduce pollution.
Technology: IoT-based air monitors and smog towers track pollution in real-time, while cleaner industrial methods help reduce emissions.
Renewable Energy: Switching to solar and wind energy reduces pollution from fossil fuels.
Public Transport & EVs: Using buses, trains, and electric cars can reduce pollution from vehicles. Carpooling also helps.
Waste Management: Proper disposal and reducing waste burning can control harmful emissions.
Community Efforts: Raising awareness and educating people about air pollution and sustainable practices empowers communities to take action. Adopting eco-friendly habits like saving energy and planting trees makes a difference.

Simple Steps to Protect Yourself from Air Pollution

Check Air Quality Daily: Stay informed about pollution levels in your area through color-coded forecasts available on local news, radio, and open-source websites.
Exercise Wisely: Avoid outdoor workouts when pollution is high. Choose indoor options like gyms or malls, and keep kids indoors if air quality is unhealthy. Even on good air days, avoid exercising near busy roads.
Save Energy at Home: Using less electricity helps reduce pollution and lowers greenhouse gas emissions. Check the EPA’s tips to conserve energy and cut costs.
Reduce School Bus Emissions: Encourage your child’s school to limit bus idling and switch to zero-emission buses with programs like the EPA’s Clean School Bus initiative.
Use Green Transport: Walk, bike, carpool, or take public transport to reduce vehicle emissions. Combine trips to reduce driving.
Avoid Burning Trash: Burning wood and trash releases harmful pollutants, so opt for cleaner alternatives.
Choose Electric Tools: Switch to electric lawn care tools instead of gasoline-powered ones to reduce pollution.
Prepare for Air Quality Disasters: Stay ready for wildfires, extreme weather, and other events that can worsen air quality.
Improve Indoor Air: Learn how to keep the air in your home clean and safe to breathe.
Speak Up for Clean Air: Support policies for cleaner air by engaging with initiatives like the IAQN community and sharing your concerns with policymakers.

The data we’re analyzing was collected in real-time on January 23rd, 2025, from the AQI Bulletin of CPCB and real-time IQAir.

It’s just a snapshot of that day so that the numbers can change daily. This gives us a good idea of the air quality on that day, but tomorrow’s data might look different. Real-time data keeps changing all the time."

Conclusion

The list of the top 5 most polluted cities in India for 2025 gives a clear picture of the country's air pollution levels. The winter season and various sources of emissions are the main reasons for poor air quality at the start of the year. This situation calls for immediate action to ensure cleaner air for everyone in India.

Tackling air pollution is important for both people's health and the well-being of communities. As air quality worsens in many parts of the world, it's essential for both governments and individuals to take action to reduce emissions and improve the air we breathe. Let’s make informed decisions today for a cleaner, safer tomorrow, support cleaner cities, reduce pollution, and improve the air we breathe.