Toxic air, rising risks: How many cigarettes are we smoking without lighting up?
Delhi suffers severe winter air pollution due to weather conditions, stubble burning, and traffic. The Air Quality Index monitors eight pollutants. While Kochi fares better, Delhi implemented strict vehicle and construction bans.
Delhi suffers severe winter air pollution due to weather conditions, stubble burning, and traffic. The Air Quality Index monitors eight pollutants. While Kochi fares better, Delhi implemented strict vehicle and construction bans.
Delhi suffers severe winter air pollution due to weather conditions, stubble burning, and traffic. The Air Quality Index monitors eight pollutants. While Kochi fares better, Delhi implemented strict vehicle and construction bans.
With the onset of winter, Delhi invariably finds itself gasping for clean air. This year, however, the national capital recorded its highest-ever air pollution levels as early as November. Why does pollution spike in Delhi during winter? How does the situation compare with other parts of the country? Is Keralam's air quality any better? And how are pollution levels measured? Here are the answers.
Why does Delhi struggle to breathe?
During winter, toxic gases and fine particulate matter build up in the atmosphere to dangerous levels, leaving Delhi struggling to breathe. Its geographical location and changing weather conditions further aggravate the problem. Vehicular emissions, road dust, construction activities, industrial operations, and the burning of waste and crop stubble all contribute to rising pollution levels.
Why does winter choke Delhi?
Under normal atmospheric conditions, air close to the Earth's surface gets heated and rises. During winter, however, the Earth's surface cools rapidly, causing the air near the ground to become colder. A layer of warm air forms above this cooler air, trapping pollutants and dust particles close to the ground and preventing them from rising and dispersing.
Low wind speeds during winter further aggravate the situation, allowing toxic gases and fine particulate matter to remain suspended in the atmosphere. High moisture levels, combined with smoke and dust particles, contribute to the formation of toxic smog. Besides, the burning of crop stubble after the harvest adds to the smoke and pollutants in the atmosphere.
What are the other major contributors to air pollution?
Apart from geographical factors, atmospheric conditions and human activities also play a major role in worsening air pollution. Vehicles emit pollutants such as nitrogen oxides, carbon monoxide and hydrocarbons. The problem is compounded by ageing vehicles and traffic congestion, which increase the volume of these emissions.
Road tarring and construction activities generate large amounts of dust, adding to the particulate matter suspended in the air. Industries, brick kilns and thermal power plants are other major sources, releasing fine particulate matter and harmful gases into the atmosphere. The burning of crop stubble in neighbouring states such as Punjab and Haryana after the harvest adds to the pollution burden, releasing huge amounts of smoke into the air. Firecrackers burst during Diwali also cause a sudden spike in pollution levels, leading to a sharp deterioration in air quality.
What is the Air Quality Index?
The National Air Quality Index (AQI) was introduced to monitor and assess air quality in real time. The Union Ministry of Environment launched the system in September 2014, with the Central Pollution Control Board (CPCB) responsible for implementing it across the country. Based on eight parameters, the AQI translates complex pollution data into a simple measure that helps the public understand the quality of the air they breathe. The index is updated every half an hour and can be accessed through websites such as www.aqi.in.
Which pollutants are measured to assess air quality?
The Air Quality Index is calculated based on eight major pollutants:
PM10 (Particulate Matter 10): Particles less than 10 micrometres in diameter, released from sources such as dust, construction activities and natural processes. Prolonged exposure can cause health problems.
PM2.5: Fine particles less than 2.5 micrometres in diameter. They can penetrate deep into the lungs and enter the bloodstream, increasing the risk of heart and respiratory diseases.
Nitrogen dioxide (NO₂): A gas released mainly by vehicles and power plants. Exposure can aggravate asthma and other respiratory ailments.
Sulphur dioxide (SO₂): A gas produced by burning coal and oil. It can irritate the respiratory tract and contribute to acid deposition.
Carbon monoxide (CO): A toxic gas released during the incomplete combustion of fuels. It reduces the blood's ability to carry oxygen.
Ground-level ozone (O₃): Formed when pollutants in the atmosphere react in the presence of sunlight. It can cause respiratory irritation and other breathing difficulties.
Ammonia (NH₃): Released into the atmosphere mainly through the use of chemical fertilisers in agriculture.
Lead (Pb): A toxic heavy metal released through industrial activities and battery production.
When does air quality deteriorate?
The National Air Quality Index classifies air quality into six categories based on pollution levels and their possible health effects.
Good (0–50): Air quality is satisfactory and poses little or no health risk.
Satisfactory (51–100): Sensitive individuals and those with respiratory ailments may experience mild breathing discomfort.
Moderate (101–200): Children, older people and those with existing health conditions may experience discomfort. People with respiratory or heart diseases may develop mild breathing difficulties or cough.
Poor (201–300): Symptoms may worsen among people with respiratory and heart diseases. Prolonged exposure to such air should be avoided.
Very Poor (301–400): Prolonged exposure can cause breathing difficulties, while symptoms may become more severe among people with existing health conditions.
Severe (401–500+): This is a critical level at which even healthy people may experience breathing difficulties. Those with existing health problems may be seriously affected.
How does Keralam fare on air quality?
According to 2025 data on aqi.in, Kochi ranks as Keralam's most polluted city, placing 423rd globally. Kozhikode, Thrissur, Kollam, Pathanamthitta and Thiruvananthapuram follow in the list.
Breathing Kochi's air equals smoking 78 cigarettes a month!
According to the AQI website, breathing Kochi's air for a day is equivalent to smoking an average of 2.5 cigarettes. This amounts to 18.2 cigarettes a week and 78 a month. The calculation is based on the concentration of PM2.5, the fine particulate matter present in the air.
The situation is far worse in Delhi, where breathing the air for a day is equivalent to smoking 11.8 cigarettes. Over a month, this adds up to the equivalent of 354 cigarettes.
Why can't Delhi shake off its pollution problem?
Farmers in Delhi's neighbouring states of Punjab and Haryana routinely burn crop stubble after the harvest. Burning tonnes of stubble releases huge amounts of smoke into the atmosphere, which is carried towards Delhi depending on wind direction. The problem is particularly acute during winter.
According to the government's Decision Support System, stubble burning accounted for around 18.57% of Delhi's pollution on November 1, compared with 5.33% on October 31. The festive season adds to the pollution burden, with firecrackers burst during Navratri and Diwali celebrations further aggravating the situation.
According to data for November 3, Delhi recorded an AQI of 464, placing it in the severe category. The PM2.5 concentration stood at 333 micrograms per cubic metre, while PM10 was recorded at 382 micrograms per cubic metre. Delhi currently ranks ninth among the world's most polluted cities.
What measures has Delhi taken to curb air pollution?
As part of its efforts to control air pollution, the Delhi government has banned vehicles that do not meet Bharat Stage VI (BS6) emission standards and are registered outside Delhi. The restriction will remain in force until January 31, 2027.
The government will also strictly enforce the rule prohibiting fuel stations from dispensing fuel to vehicles without a valid Pollution Under Control (PUC) certificate. Such vehicles will not be supplied with petrol, diesel, CNG or LPG. Electric vehicles, CNG vehicles and those providing essential services have been exempted from the restrictions.
Construction and demolition activities that generate dust have also been brought under restrictions during winter. Activities involving construction that generate excessive dust will face a complete ban from December 10 to January 20.
The government has further directed public and private establishments, except those providing essential services, to allow only 50% of their staff to work from the office, with the remaining employees working from home. Municipal corporation offices will function from 8.30 am to 5 pm, while Delhi government offices will operate from 10 am to 6.30 pm.
The government has also urged people to make maximum use of public transport and adopt carpooling to reduce vehicular emissions.