Delhi has recently registered its worst air quality for this season, with the city hitting the “severe” category in the Air Quality Index (AQI) for the first time. The capital's AQI spiked to a hazardous level of 418, up from 334 the previous day. The Central Pollution Control Board (CPCB) attributed this surge to “unprecedentedly dense” fog, which has trapped pollutants in the atmosphere. Currently, the Commission for Air Quality Management (CAQM) is monitoring the situation but has yet to impose stage three of the Graded Response Action Plan (GRAP). Authorities have warned, however, that restrictions could be imposed if air quality does not improve.
Delhi’s AQI, recorded at 418, falls into the “severe” category, posing significant health risks for the entire population. The AQI scale indicates that levels between 401 and 450 are “severe,” meaning that prolonged exposure could lead to respiratory issues and worsen pre-existing heart conditions. In comparison to other affected regions, Bihar’s Hajipur recorded an AQI of 417 on the same day. However, the dense urban environment of Delhi amplifies the impact of these hazardous levels of pollution.
Data from the CPCB showed that 30 out of Delhi’s 36 air quality monitoring stations recorded AQI levels in the “severe” range, emphasizing the widespread nature of this pollution event. Such critical levels are typically seen only a few times each year, mostly during winter, when atmospheric conditions such as low temperatures, minimal wind speed, and dense fog can trap pollutants. From the start of the year until November 12, Delhi experienced 116 days with AQI levels in the “poor,” “very poor,” or “severe” categories, which left only 201 days in the “good” or “moderate” range.
The recent AQI spike is largely due to local factors, with vehicular emissions contributing significantly. On Wednesday, vehicular pollution alone was responsible for 13.3% of the total air pollution in Delhi. Emissions from cars, buses, and trucks release a mix of pollutants, including particulate matter (PM) and nitrogen dioxide, that contribute to the city’s air quality issues.
The particulate matter in Delhi’s air, specifically PM2.5 and PM10, poses severe health risks. PM2.5 refers to fine particulate matter measuring 2.5 micrometers or smaller. These tiny particles can enter the lungs and penetrate the bloodstream, leading to respiratory issues, cardiovascular diseases, and even cancer. PM10 particles are coarser, measuring 10 micrometers or less, and though less likely to enter the bloodstream, they can still cause respiratory problems. According to CPCB data, Delhi’s annual PM10 and PM2.5 levels have risen by 5% and 7% this year, respectively, indicating a worsening trend in air quality.
In addition to vehicular emissions, other factors contributing to Delhi’s pollution include dust from construction sites, industrial emissions, and crop residue burning in neighboring states. Crop burning is a common practice in Punjab and Haryana, where farmers burn leftover crop stubble to clear the fields for the next planting season. The smoke from these fires drifts into Delhi, adding significant particulate matter to the air. This seasonal practice is one of the major reasons behind the surge in pollution levels during winter.
Delhi’s recent spike in pollution is also linked to specific weather conditions, particularly fog. The season’s first dense fog event, combined with low daytime temperatures, resulted in an “unprecedentedly dense” fog that trapped pollutants near the ground. The maximum temperature recorded in Delhi’s Safdarjung area dropped from 32.8°C on Tuesday to 27.8°C on Wednesday. The fog significantly reduced visibility, with reports from the India Meteorological Department (IMD) noting that visibility levels at Delhi’s Indira Gandhi International (IGI) Airport dropped to zero, leading to flight delays. Visibility in other areas was limited to just 125 meters. According to the IMD, the combination of low temperatures, calm air, and dense fog created a situation where pollutants could not disperse, leading to the high AQI levels observed in Delhi.
The impact of such severe air quality on public health is significant. Dr. L.M. Darlong, head of thoracic oncosurgery at the Rajiv Gandhi Cancer Institute, pointed out that PM2.5 can lead to lung cancer by causing genetic mutations that promote uncontrolled cell growth in the lungs. The small size of PM2.5 particles allows them to bypass the respiratory system’s defenses, leading to deeper penetration into lung tissue and even the bloodstream. The onset of symptoms may not occur until the later stages of disease development, making early diagnosis challenging.
In response to the deteriorating air quality, authorities are considering enacting stage three of the Graded Response Action Plan (GRAP) if pollution levels persist. Stage three of GRAP includes stricter measures, such as a construction ban and prohibiting the use of older vehicles, specifically BS-III petrol and BS-IV diesel vehicles, to reduce emissions. These measures are intended to reduce pollutant levels rapidly and curb the health risks posed by sustained “severe” air quality.
If implemented, the construction ban will target dust emissions from ongoing projects, which significantly contribute to PM10 levels in Delhi. Additionally, by limiting the use of older, less efficient vehicles, authorities hope to decrease nitrogen dioxide and particulate matter emissions. The need for stricter measures has been emphasized by CPCB officials, who noted that the combination of low temperatures, high humidity, and near-zero wind speeds makes pollution control efforts critical at this time of year.
The CAQM’s decision to monitor the situation before imposing further restrictions reflects the complex balance needed to address Delhi’s air quality issues. While immediate measures like GRAP can provide short-term relief, they highlight the ongoing challenge of maintaining healthier air quality levels in Delhi. The high levels of pollution recorded this season underscore the need for effective, long-term interventions to mitigate the factors contributing to Delhi’s pollution crisis.
Delhi’s air quality crisis is a clear warning about the health risks of high pollution levels. With winter progressing, the city could see more severe air quality episodes. Urgent actions and long-term solutions are needed to address pollution's root causes and protect public health. The city calls for joint efforts of the government, institutions, and residents to tackle the concerning state of pollution in the national capital territory.
