Helena Joyce
Delhi is often considered the most polluted city in the world. The air quality is said to be the worst from November to February, with AQI levels routinely eclipsing 700, indicating hazardous conditions. During the crop-burning season, stubble burning in Haryana and Punjab can account for up to 45% of Delhi's pollution. The city's air pollution is also influenced by thermal power plants, vehicle emissions, wood-burning fires, and industrial activities. Notably, Delhi's air pollution is typically at its worst between 6 am and noon, with PM2.5 levels peaking around 9 am.
| Characteristics | Values |
|---|---|
| Time of day with worst pollution | 6am to noon |
| Highest PM2.5 concentration | 488 micrograms per cubic metre (µg/m3) at 12pm |
| National acceptable limit for PM2.5 | 60µg/m3 |
| Average lowest PM2.5 concentration | 156 ug/m3 at 5 and 6pm |
| Average PM2.5 concentration at 9am | 128 micrograms |
| Average PM2.5 concentration at 5pm | 66 micrograms |
| WHO's annual mean recommendation for PM2.5 in 2021 | 5 μg/m3 |
| WHO's annual mean recommendation for PM2.5 in 2005 | 10 μg/m3 |
| Worst AQI level in New Delhi | 132 (Poor) at 11:09 AM |
| Worst air quality season in Delhi | November to February |
| Worst AQI reading in Delhi | 491 on November 18, 2024 |
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What You'll Learn
Morning walks are harmful due to high pollution levels
Delhi is often regarded as the world's most polluted city, and its air pollution is particularly severe from November to February. During this period, the air quality index (AQI) often exceeds 400, indicating hazardous conditions with significant health impacts.
Morning walks in Delhi can be harmful due to high pollution levels. Data from the Central Pollution Control Board (CPCB) shows that air pollution is typically at its worst between 6 am and noon. During this time, pollutants accumulate due to calm winds, creating a thick haze. The concentration of PM2.5 particles, which are harmful to human health, peaks within this window, reaching levels multiple times higher than the 24-hour national acceptable limit.
The impact of high pollution levels on athletes and the general public has been significant. Delhi's chief athletics coach, Dinesh Rawat, noted that athletes have been experiencing breathing issues and eye irritation during morning training sessions. Health experts advise avoiding morning walks when smog is present, as pollutants are at surface level during this time. Dr G C Khilnani, chairman of the PSRI Institute of Pulmonary, Critical Care and Sleep Medicine, recommends exercising later in the day when the sun is out and pollution levels have reduced.
Delhi's air pollution is influenced by various factors, including vehicle emissions, wood-burning fires, agricultural fires, industrial activities, and construction dust. The impact of these sources is exacerbated by stagnant winds, which trap smoke and emissions, leading to dangerous levels of air pollution.
To address the issue of high pollution levels, the government has implemented various measures, including the formation of the Commission for Air Quality Management, the regulation of dust, and the banning of diesel generators in certain areas. Additionally, Punjab has launched initiatives to reduce stubble burning, a major contributor to air pollution in Delhi. These collective efforts aim to improve air quality and mitigate the harmful effects of pollution on the health and well-being of Delhi's residents.
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Calm winds and vehicle emissions contribute to high pollution
Delhi is often considered the most polluted city globally, with pollution levels exceeding annual mean concentration recommendations. The air quality is at its worst from November to February, with PM2.5 levels peaking between 6 am and noon, specifically at 9 am, when the concentration reaches 128 micrograms. This is over 12 times the World Health Organization's annual limit.
Calm winds and vehicle emissions significantly contribute to this high pollution. Winds are often calm from late evening onwards, allowing pollutants to accumulate overnight and in the early hours. The increase in temperature around noon causes a brief respite, with winds blowing at the surface level. However, by 6 pm, the temperature drops again, leading to calm wind conditions and a slight increase in pollution levels. This pattern shows how calm winds impact the dispersion of pollutants.
Vehicle emissions also play a crucial role in Delhi's high pollution levels. The number of vehicles on the roads increases after 7 am, and if there are no winds, their emissions accumulate, leading to a high concentration of pollutants in the air before noon. Motor vehicle emissions are a significant cause of poor air quality, along with wood-burning fires, cow dung cake combustion, fires on agricultural land, exhaust from diesel generators, dust from construction sites, burning garbage, and illegal industrial activities.
The combination of calm winds and vehicle emissions results in a high concentration of pollutants in the morning, particularly between 6 am and noon. This trend has been observed through data, which shows that exercising outdoors in the morning can be harmful, especially for athletes and vulnerable populations. The air quality gradually improves as the day progresses, with PM2.5 levels decreasing by almost half at 5 pm compared to 9 am.
To address the issue of calm winds and vehicle emissions, it is essential to implement measures such as improving wind circulation, reducing vehicle emissions, and regulating industrial activities. By taking such actions, Delhi can work towards improving its air quality and reducing the health risks associated with high pollution levels.
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Delhi's air quality is worst from November to February
Delhi is often called the most polluted city in the world. The air quality index (AQI) in Delhi generally falls within the Satisfactory (51–100) and Moderate (101–200) ranges between March and September. However, it drastically deteriorates to Poor (201–300), Severe (301–400), or Hazardous (401–500+) levels between October and February. On the worst days, the AQI exceeds 400.
Delhi's air quality is at its worst from November to February. During this period, the air quality is affected by the burning of effigies during Vijayadashami, the bursting of firecrackers during Diwali, and the impact of local sources such as the transport sector. On 18 November 2024, Delhi recorded its worst air quality of the season, with a 24-hour AQI reading of 491, classified as "severe plus". This level indicated hazardous conditions with significant health impacts, particularly for vulnerable populations.
The primary sources of smoke contributing to Delhi's poor air quality are power plants, stubble burning, lit garbage, road dust, factories, and vehicles. Motor vehicle emissions, wood-burning fires, cow dung combustion, fires on agricultural land, and burning garbage are all causes of poor air quality in Delhi. The demand for household heating during the winter season also contributes to the poor air quality, as the burning of local organic waste, including wood and cow dung cakes, increases PM2.5 concentrations in the city.
Delhi's air pollution is also influenced by agricultural stubble burning in Haryana and Punjab, coupled with north-westerly winds. During the crop-burning season, this practice can account for up to 45% of Delhi's pollution. The impact of winds on Delhi's air quality is significant. Calm winds in the early morning hours allow pollutants to accumulate, leading to higher PM2.5 levels between 6 am and noon. As the temperature increases after noon, winds pick up, dispersing the pollutants and briefly improving air quality until the evening when wind conditions become calm again.
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Agricultural stubble burning is the biggest cause of air pollution
Delhi is often considered the most polluted city globally, with pollution levels far exceeding safe limits. The air quality is said to be worst from November to February, with the city missing clean-air standards for much of the year.
Agricultural stubble burning is a significant contributor to Delhi's poor air quality. The practice of burning crop residue after harvesting rice in the states of Punjab, Haryana, and Western Uttar Pradesh, which are north-west of Delhi, has been identified as the biggest cause of the city's air pollution. During the crop-burning season, this practice can account for up to 45% of Delhi's pollution. The smoke from these fires, along with emissions from vehicles, industries, power plants, and residential sources, accumulates overnight and in the early morning hours due to calm winds, leading to extremely high levels of pollutants during this time.
The burning of stubble releases toxic pollutants and gases, such as carbon monoxide and methane, into the atmosphere. This not only affects Delhi but also has severe health risks for the local and regional populations in the areas where stubble burning occurs. The smoke from these fires, combined with vehicle emissions and other sources, results in a thick layer of haze that reduces visibility and has led to accidents, transport cancellations, and delays.
The impact of stubble burning on Delhi's air quality is evident in the PM2.5 concentration levels, which are often multiple times higher than the recommended limits. On some days, the PM2.5 levels in Delhi have been recorded at 488 micrograms per cubic meter, eight times the 24-hour national acceptable limit of 60 micrograms per cubic meter. The high levels of PM2.5 pollutants have severe health impacts, particularly for vulnerable populations, and can cause respiratory issues and eye irritation, as reported by athletes and cricketers visiting Delhi.
To address the issue of stubble burning, the central government launched the Promotion of Agricultural Mechanisation for In-situ Management of Crop Residue scheme in Punjab, Haryana, Uttar Pradesh, and Delhi NCR. This scheme subsidizes the cost of in-situ crop residue management (CRM) equipment to encourage their adoption and provide alternatives for dealing with crop residue effectively. Despite these efforts, stubble burning continues to be a challenging issue, with governments facing criticism for failing to enforce anti-pollution measures and implement penalties for burning stubble.
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Delhi is often called the most polluted city in the world
There are several factors contributing to Delhi's poor air quality. Motor vehicle emissions are a significant cause, with the number of vehicles on the road increasing pollution levels. Other sources include wood-burning fires, cow dung cake combustion, fires on agricultural land, exhaust from diesel generators, dust from construction sites, burning garbage, and illegal industrial activities. Delhi's air quality is also affected by stubble burning in nearby states, with crop-burning accounting for up to 45% of the city's pollution during the harvest season. The impact of these sources is exacerbated by stagnant winds and cold weather, which trap the various sources of smoke.
The high levels of air pollution in Delhi have severe health implications for its residents. Athletes have reported breathing issues and a burning sensation in their eyes, and children, who are among the most vulnerable to pollution-related illnesses, have had to stay home from school. Health experts advise residents to avoid going outdoors, especially in the mornings when pollution levels are typically at their highest. The pollution has also disrupted transportation services, with delays and cancellations of public transport, primarily trains and flights.
To combat air pollution, the government has implemented various measures. The Commission for Air Quality Management was set up to enforce pollution control in the National Capital Region (NCR). A dedicated pollution control team has been managing complaints and regulating dust, and diesel generators have been banned in select areas. Additionally, the state of Punjab has launched farming incentives, such as the MSP scheme for alternative crops, to reduce stubble burning. Despite these efforts, Delhi continues to face significant challenges in improving its air quality and protecting the health and well-being of its residents.
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Frequently asked questions
Between 6 am and noon, with the peak at 9 am.
Pollutants accumulate overnight and in the early hours due to calm winds, and vehicles on the road from 7 am add to the emissions.
Motor vehicle emissions, wood-burning fires, cow dung combustion, fires on agricultural land, diesel generator exhaust, dust from construction sites, burning garbage, and illegal industrial activities.
The air quality improves gradually as the day progresses, with the least concentration of PM2.5 on average around 6 pm.
Delhi recorded its worst air quality reading on November 18, 2024, with a 24-hour AQI of 491, classified as "severe plus."
