Delhi's Air Pollution: A Critical Analysis

Delhi, the capital city of India, is known for its alarmingly high levels of air pollution. The city's poor air quality is a result of various factors, including vehicular emissions, industrial activities, crop stubble burning, and dust. These sources contribute to the high levels of particulate matter (PM2.5 and PM10) and harmful gases in the air, which have severe health implications for Delhi's residents and visitors. While efforts have been made to address this issue, such as the implementation of the Commission for Air Quality Management and the use of smog towers, Delhi continues to face significant challenges in improving its air quality.

Delhi's air pollution is largely caused by vehicular emissions, industrial activities, and crop stubble burning

Delhi, the capital of India, is one of the biggest commercial and economic powerhouses of the country. The city has witnessed a large-scale expansion of its service sector, with many people migrating to work in fields like IT, telecommunications, tourism, and the hotel industry. While this has been beneficial for the economy, it has also resulted in a significant increase in pollution levels.

Delhi's air pollution is largely attributed to vehicular emissions, industrial activities, and crop stubble burning. Vehicular emissions, including motor vehicles and road dust, are major contributors to the poor air quality in Delhi. In 2018, India's Ministry of Earth Sciences attributed almost 41% of Delhi's air pollution to vehicular emissions. More recent data from 2024 shows that vehicular emissions accounted for 13.7% of the city's pollution. The resumption of work after the Diwali weekend, with offices reopening and increased commuter traffic, further exacerbates this issue.

Industrial activities also play a significant role in Delhi's air pollution. In 2018, industrial emissions were responsible for 18% of the city's air pollution, according to the Ministry of Earth Sciences. Within Delhi and its surrounding areas, industries contribute 3.4% to the region's pollution levels. This includes emissions from power plants, which are a significant source of NOx and SO2 emissions.

Crop stubble burning in neighbouring states, such as Haryana and Punjab, significantly impacts Delhi's air quality. During the crop-burning season, this practice can account for up to 45% of Delhi's pollution, according to government meteorologists. On certain days, stubble burning contributed almost 15% to 20% of Delhi's pollution. The burning of crops, along with fires on agricultural land, releases harmful pollutants and toxic metals into the atmosphere.

In addition to these primary sources, there are other factors contributing to Delhi's air pollution crisis. Residential sources, waste burning, and construction activities add to the multifaceted nature of the problem. Pollution from neighbouring cities, such as Ghaziabad, Noida, Gurugram, and Faridabad, also plays a significant role, underscoring the need for coordinated policy responses across the National Capital Region to effectively address this annual challenge and improve air quality for Delhi's residents.

The city's low wind speeds and temperature inversions trap smoke and emissions, exacerbating pollution

Delhi, India's capital, has been facing severe air pollution for years. In 2021, the city's air quality index (AQI) reading of 362 was classified as "severe", indicating hazardous conditions with significant health impacts. The city's low wind speeds and temperature inversions, along with other factors, trap smoke and emissions, exacerbating pollution levels.

Low wind speeds in Delhi prevent the dispersion of pollutants, allowing them to accumulate in the air. The wind speed in the city has been recorded at approximately 4 kmph, which is significantly lower than the previous speed of 10 kmph. This reduction in wind speed, coupled with a decrease in the atmospheric mixing height, contributes to the deterioration of air quality. The atmospheric mixing height refers to the point where the lower atmosphere meets the upper atmosphere, facilitating the dispersion of pollutants. When wind speed is insufficient, pollutants are not effectively carried upwards and mixed with cleaner air, leading to their buildup in the lower atmosphere.

Temperature inversions also play a significant role in trapping smoke and emissions. In normal conditions, hot air rises, carrying pollutants upwards and away from the ground. However, during a temperature inversion, the environmental temperature profile deviates from the norm, resulting in warmer air trapped above a layer of cooler air closer to the ground. This inversion acts as a "cap", preventing the upward movement of pollutants and trapping them at lower altitudes. The height of smokestacks or chimneys that expel pollution is also a factor. If they are not tall enough to emit pollution above the inversion height, it can result in pollution being trapped close to the ground.

The combination of low wind speeds and temperature inversions creates stagnant weather conditions that favour the formation and accumulation of fine particulate matter, leading to the exacerbation of pollution levels in Delhi. These factors, along with other sources of emissions, contribute to the city's severe air quality issues.

To address the air pollution crisis, various initiatives have been proposed, including the creation of a 1,600 km long and 5 km wide green ecological corridor along the Aravalli Range from Gujarat to Delhi, connecting to the Sivalik Hills range. Additionally, the planting of 1.35 billion new native trees over 10 years has been suggested to combat pollution. These initiatives aim to mitigate the severe air pollution in Delhi, which has led to detrimental health effects on its residents.

Air pollution levels are typically worse during the winter months, often entering the severe category

Delhi, India's capital, is the world's most polluted city. The air quality index (AQI) in Delhi typically falls within the moderate range between March and September. However, from October to February, the AQI levels in Delhi routinely deteriorate to the poor, severe, or hazardous categories. During these winter months, the AQI often exceeds 700, posing severe health risks, especially to vulnerable populations.

Several factors contribute to Delhi's severe air pollution during the winter. One major factor is stubble burning, where farmers burn crop residue to clear fields. In 2023, stubble burning accounted for 38% of Delhi's air pollution. This practice is more common during the winter months, with crop burning in nearby states spiking pollution levels and contributing over 45% of total pollution during the peak season.

Vehicular emissions are another significant source of air pollution in Delhi, attributed to almost 41% of total pollution. Cars, buses, and trucks emit carbon monoxide, nitrogen oxides, and particulate matter, with vehicles contributing 20% of PM2.5 and 36% of NOx emissions. Industrial pollution also plays a role, with factories and power plants releasing large amounts of SO2 and NOx. About 90% of Delhi's SO2 emissions originate from industrial sources.

Other factors exacerbating Delhi's air pollution during the winter include low wind speeds, temperature inversions, and cold weather, which trap smoke and emissions, creating long-lasting smog. The burning of effigies during Vijayadashami, the bursting of firecrackers during Diwali, and wood, cow dung, and landfill fires also contribute to the hazardous levels of PM2.5 and PM10 particulate matter during the winter months.

The severe air pollution in Delhi during the winter has led to the implementation of various measures to combat the issue. The Commission for Air Quality Management was established to enforce pollution control, and a 10-member Pollution Control Team manages complaints and regulates dust. The Delhi government has also considered remote work policies and the closure of schools and government offices during periods of severe air pollution. Additionally, initiatives such as the installation of smog towers and the Pusa Bio-Decomposer to reduce stubble burning are being explored to improve Delhi's air quality.

Delhi's air quality index (AQI) has worsened over the years, with an average percentage change of 1.84% from 2020 to 2025

In May 2025, Delhi's AQI was recorded at 167, indicating a decline in air quality compared to the previous year. Several factors contribute to Delhi's poor air quality, including stubble-burning, vehicular emissions, industrial pollution, and low wind speeds. The practice of stubble-burning, where farmers burn crop residue to clear fields, has been a significant concern, with crop burning in nearby states contributing over 45% of total pollution during the winter peak season.

Vehicular emissions, including those from cars, trucks, and two-wheelers, release carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM) into the atmosphere. In addition, aged vehicles and those running on diesel or lower-quality fuels emit higher levels of pollutants and fumes. Industrial sources, such as factories and power plants, are responsible for about 90% of Delhi's SO2 emissions and contribute significantly to smog and haze.

The service sector's expansion has also played a role in Delhi's air pollution. The city's growing economy has attracted migration and increased anthropogenic activity, construction, and roadwork, which contribute to dust and particulate matter pollution. Additionally, factors such as urban topography, cold temperatures, lack of wind, and high humidity levels can exacerbate the build-up of pollution, trapping smoke and emissions and creating long-lasting smog.

The poor air quality in Delhi has severe health implications for its residents. Even healthy individuals can experience significant physical damage from exposure to hazardous levels of PM2.5. More vulnerable groups, including young children, the elderly, pregnant women, and those with pre-existing health conditions, are at an even higher risk of adverse health effects. To address the air pollution crisis, the Delhi government has implemented various measures, including the formation of the Commission for Air Quality Management and the launch of initiatives like the Pusa Bio-Decomposer to reduce stubble burning.

The Indian government has implemented various initiatives to combat air pollution, including the Commission for Air Quality Management and incentives for alternative farming practices

Delhi, India's capital city, is the most polluted city in the world. The air quality levels in the city are a severe health challenge, with the annual mean concentration of particulate matter PM10 and PM2.5 often exceeding safe thresholds. During winter, from October to February, Delhi's AQI levels routinely eclipse 700, posing severe health risks.

The Indian government has implemented various initiatives to combat air pollution, recognizing the urgent need for action. One notable initiative is the formation of the Commission for Air Quality Management (CAQM), tasked with enforcing pollution control in the National Capital Region (NCR). The CAQM works alongside a 10-member Pollution Control Team, which manages complaints, regulates dust, and enforces bans on diesel generators in specific areas through the "Green Delhi" app.

To address the issue of stubble burning, a significant contributor to Delhi's air pollution, the government has promoted alternative farming practices. Punjab, for instance, launched the MSP scheme for alternative crops, incentivizing farmers to reduce stubble burning. Additionally, the Pusa Bio-Decomposer technology has been introduced to manage crop residue and prevent harmful burning practices.

The Indian government has also explored technological solutions, such as installing "smog towers" across Delhi to purify the air. Furthermore, the National Clean Air Programme (NCAP) has been established, setting time-bound goals for improving air quality across the country, with a focus on 132 "non-attainment" cities that fail to meet air pollution standards. The NCAP provides a framework for developing air quality management plans and guiding policies across sectors.

Other initiatives include the Graded Response Action Plan (GRAP), which categorizes air quality into four escalating stages, triggering stricter pollution control measures. Stage I of GRAP includes dust mitigation at construction sites, effective waste management, and regular road cleaning. The government has also emphasized expanding renewable energy, promoting electric vehicles, and supplying LPG cooking fuel to households.

While these initiatives demonstrate India's commitment to tackling air pollution, the problem is complex and requires sustained efforts, collaboration, and innovative solutions involving various stakeholders to bring about meaningful change.

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