The Air Quality Index (AQI) indicates how clean or polluted the air is in a particular area. A higher AQI indicates poorer air quality and greater levels of pollution.
Following the deterioration, the Commission for Air Quality Management (CAQM) implemented Stage II of the Graded Response Action Plan (GRAP) across Delhi-NCR. GRAP is a mechanism under which restrictions and emergency measures are introduced at different levels depending on the severity of air pollution.
By 8 am on November 3, Delhi’s average AQI had climbed further to 330. Visibility had also deteriorated significantly. In areas where residents could previously see Delhi’s monuments from their rooftops, visibility had fallen to less than 100 metres.
Delhi has 60 monitoring stations to measure air quality. According to the latest updates available on the official website, readings were being received from 57 stations, while three stations were not reporting data.
However, the recurring deterioration in air quality at the beginning of every winter raises several questions. Why does Delhi's air become so polluted every year as temperatures fall? Is stubble burning the primary reason, or do pollution sources within the capital contribute more significantly? Are the measures introduced by the government sufficient to address the problem?
Dr Anju Goel, Senior Researcher and Associate Director at The Energy and Resources Institute (TERI), says weather conditions will continue to make Delhi vulnerable to worsening air quality during winter.
Vehicles, factories, construction activities and waste burning release smoke and dust into the atmosphere throughout the year. However, the rate at which these pollutants disperse differs between summer and winter.
During winter, the air near the ground is sometimes colder than the air above it. This creates a condition in which the cooler air close to the surface cannot rise easily. When wind speeds are also low, smoke and dust accumulate near the ground, worsening pollution levels.
Wind direction is another important factor. When winds blow towards Delhi from regions where stubble burning is taking place, they can carry smoke from those areas into the capital.
According to Dr Goel, weather conditions cannot be controlled. Governments must therefore focus on reducing pollution throughout the year at the sources responsible for releasing smoke and dust into the atmosphere.
Stubble Burning Is Not the Only Cause of Delhi's Pollution
Dr Goel says Delhi's air pollution cannot be attributed solely to stubble burning.
Her research found that agricultural ammonia-related pollution accounted for 27 per cent of the contribution. Vehicles and other modes of transport accounted for 23 per cent, waste and the burning of materials such as wood contributed 20 per cent, while dust accounted for 17 per cent.
Some fine particulate matter enters the atmosphere directly through smoke and dust. Other particles are formed when different gases present in the air react with one another.
According to Dr Goel, stubble burning accounts for approximately 4 per cent of Delhi's pollution on an annual average basis. However, its contribution can increase substantially on certain days.
Data from the Centre for Science and Environment (CSE) shows that stubble burning contributed an average of 4.2 per cent to Delhi's pollution during October and November 2025. In November, its contribution temporarily increased to more than 22 per cent.
By December, the contribution from stubble burning had fallen to just 0.2 per cent. Despite this decline, the average concentration of PM2.5 in Delhi's air increased from 163 to 210 micrograms per cubic metre.
This indicates that Delhi's air quality deteriorated further even after the contribution from stubble burning had almost disappeared.
Stubble burning is therefore one of the sources of pollution, but it does not explain the entire picture behind Delhi's worsening air quality. These figures are research-based estimates and do not represent a direct calculation of pollution on any particular day.
On November 3, Delhi Environment Minister Manjinder Singh Sirsa accused the Aam Aadmi Party government in Punjab of encouraging stubble burning.
The Punjab unit of the Aam Aadmi Party rejected the allegation. The party said the photograph cited by the minister did not show officials setting fire to a field but showed them attempting to extinguish a fire.
The party also questioned the BJP government in Delhi, asking why it had failed to control pollution in the capital.
However, the number of stubble-burning incidents in a particular state and the amount of smoke from those fires that reaches Delhi on a specific day are two different questions.
Records of fire incidents in agricultural fields can help establish how frequently stubble burning has taken place. Determining how much of that smoke reaches Delhi on a particular day, however, requires an examination of wind direction and the contribution of different pollution sources.
In its November 2 order, the Commission for Air Quality Management referred to prevailing weather conditions. However, it did not specify how much stubble-burning smoke contributed to the deterioration in Delhi's air quality that day.
Delhi Government's 10-Point Winter Pollution Plan
The Delhi government has introduced a 10-point action plan to tackle air pollution during the winter season.
Under the plan, 500 petrol pumps equipped with cameras capable of reading vehicle number plates are supposed to deny fuel to vehicles without a valid Pollution Under Control (PUC) certificate.
The government has also announced restrictions on the entry of vehicles registered outside Delhi that run on petrol or diesel and do not meet BS-VI emission standards.
The plan, which will remain in effect from November 1 to February 28, also includes road repairs and cleaning, measures to reduce dust generated by construction activities and increased monitoring to prevent the open burning of waste.
Chief Minister Rekha Gupta has said that better coordination among different agencies is necessary to ensure that these decisions are implemented on the ground.
However, questions remain over whether these measures will be sufficient to prevent the recurring rise in pollution levels every winter.
Can GRAP Alone Improve Delhi's Air Quality?
Bhawreen Kandhari, an environmental activist from Delhi and co-founder of Warrior Moms, says pollution-control regulations already exist, but they are not properly enforced in several areas.
According to her, firecrackers continued to be burst even after Dussehra. Construction activities were also seen continuing, while problems such as haphazard parking and traffic congestion remained unresolved.
Kandhari says the government has held meetings with different departments, but the efforts made so far have not been sufficient.
She argues that spraying water on roads and implementing GRAP after air quality has already deteriorated cannot resolve the entire problem.
GRAP is designed to trigger immediate measures when pollution crosses specified thresholds. However, addressing the actual sources of pollution requires sustained action throughout the year rather than temporary restrictions during the winter months.
Why Did Delhi's Artificial Rain Experiment Fail?
Last year, the Delhi government attempted to induce artificial rainfall to reduce the concentration of pollutants suspended in the air.
According to a BBC Hindi report dated October 29, 2025, a trial was conducted in Delhi in which fine particles were released into clouds in an attempt to trigger rainfall. However, the experiment did not produce rain.
At the time, the Delhi government claimed that the concentration of airborne particles had declined in the areas where the experiment was conducted.
However, a reduction in particulate matter does not automatically establish that the experiment itself was responsible for the improvement.
To determine whether the trial had any impact, it is also necessary to examine wind speed and direction during the same period. Changes in air quality in areas where the experiment was not conducted would also need to be assessed.
According to the World Meteorological Organization, this technique involves releasing fine particles into existing clouds to influence the process through which water droplets form.
However, the technique cannot create new rain-bearing clouds.
This means artificial rainfall cannot be induced unless suitable clouds are already present in the atmosphere. Consequently, the method cannot be used every time Delhi's air quality deteriorates.
What Needs to Be Done Throughout the Year to Improve Air Quality?
According to Dr Goel, the air quality of Delhi and its surrounding regions is interconnected. Therefore, Delhi cannot improve its air quality through independent action alone.
Governments and different agencies in Delhi and neighbouring states must coordinate their efforts to reduce pollution.
Dr Goel says it is important to enforce vehicle emission standards such as BS-VI. The existing system of Pollution Under Control (PUC) testing for vehicles already operating on roads also needs to be strengthened.
Rules to control dust during road construction and building activities must be properly implemented.
She also highlights the need to promote cleaner cooking alternatives, including stoves that produce less smoke.
However, Dr Goel points out that adopting LPG is not financially feasible for every household. Pollution-control policies must therefore consider whether families can afford the alternatives being proposed.
Bhawreen Kandhari also highlights the political dimension of the pollution crisis.
She believes that unless pollution becomes an election issue, governments will not face sufficient public pressure to address it effectively.
Dr Goel, meanwhile, says governments are taking steps to tackle the problem, but considerably more work remains to be done.
Are Delhi's Air Quality Levels Actually Improving?
Air pollution is not a new problem for Delhi. Records of the city's pollution levels are available dating back to at least the 1990s.
However, the methods used to measure pollution during that period were different from the AQI system used today. Therefore, the figures cannot be directly compared.
Recent data indicates some improvement in Delhi's annual pollution levels.
According to the Centre for Science and Environment, the annual average PM2.5 concentration in Delhi stood at 105 micrograms per cubic metre in 2024. It declined to 97 micrograms per cubic metre in 2025.
However, this level remains more than twice India's annual standard of 40 micrograms per cubic metre.
Furthermore, the average PM2.5 concentration in December 2025 was 24 per cent higher than in December 2024.
This suggests that even though the annual average has improved, winter pollution can still become more severe.
The key question is whether Delhi's air quality is genuinely improving or whether the decline in the annual average is masking worsening conditions during the winter months.
It is also important to determine whether residents of highly polluted areas such as Jahangirpuri, Bawana and Anand Vihar are benefiting from the reported improvement.
These questions cannot be answered through AQI readings from a single day. A reliable assessment requires pollution data collected over several months and years, across different locations.
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