Delhi's charms are unpredictable. The chaotic streets, the unruly traffic and polluted air, the aggressive inhabitants and their hurried lives, and the tolerance for the obnoxious constitute an integral part of this phenomenal city. In beauty resides horror, and vice versa!

Struggling to breathe under the angry modern façade of the megalopolis is a parallel world, time-worn and easily missed, that teems with art, heritage and poetry.

Every winter, India's national capital grabs global headlines for an unpleasant phenomenon. As the mercury starts dipping, Delhi, along with its neighbouring suburbs of Noida, Gurgaon, Ghaziabad and Faridabad, together termed as the National Capital Region (NCR), gets engulfed in a thick blanket of hazardous smog for 10-12 weeks, putting the health of its residents at severe risk from various respiratory disorders.

This unpleasant situation has made the city the 'most polluted city in the world.'

It raises the question of why no one is trying to save this city; no one wants to wipe out the tag of the most polluted city. If we try to find the answer, the answer may surprise you: the city has consistently been planning almost everything to fight the menace of air pollution. The strategies and actions are ritually and vigorously repeated year after year, thus making Delhi the most experimented and studied city in this domain and yet struggling to breathe every winter.

It prompts us denizens to ask what is wrong with this region and why we repeatedly fail to control this menace.

Nature's curse: A landlocked city

Delhi is a landlocked city. The distance from the sea gives it an extreme continental climate with the prevalence of continental air during significant periods of the year.

Meteorologically speaking, the average temperature in Delhi during winter is around 14 °C (57 °F), but temperatures can range from 22°c to 2°C. Delhi is known for its heavy fog and haze during winter, which can disrupt road, air, and rail traffic. Winter in Delhi usually begins in late November or early December and ends in the first week of March. Delhi's proximity to the Himalayas can lead to cold waves, lowering the apparent temperature due to wind chill.

In the winter, two peaks of air pollution could be observed in Delhi – the first with the onset of winter in October and continuing till November, and the second from mid-December to January.

Both have different causes. The first is mainly influenced by the onset of winter, slowing wind speed, change in wind direction, and increasing vehicular movement due to festive occasions. Post-harvest activities like burning agricultural residue also contribute to the condition. At the same time, the second peak is highly influenced by low-temperature calm conditions, low solar index and high and varying humidity.

Metrological condition, therefore, plays a crucial role in both phases. Increased wind velocity and a few hours of winter rain improve the situation by washing out the pollutants or dispersing them.

The primary concern with particulate matter is its dual impact: it directly affects visibility while posing significant short-term and long-term health risks. The environmental health cost may be phenomenal with the most affected being people with co-morbidities while the young and senior citizens are also significantly vulnerable.

The graphic lists the air quality status in Delhi in October and November, which shows almost the same pattern in the five years since 2019.

 The following factors have a significant impact on air quality status

- Wind direction changes from south-westerly to north-westerly in early or mid-October. 

- Temperature: The average monthly temperature in Delhi is around 28°C maximum and 13–14°C minimum in November. 

- Rain: There is little or no rain in November. 

- Wind speed: The average wind speed in Delhi is 2.4 m/s, with a maximum of around 8 m/s. 

- Humidity: The average relative humidity in Delhi is around 66.5%. 

- Pressure: The station pressure in Delhi varies from 984 hectopascals (hPa) to 965 hPa, averaging around 1000 hPa. 

Not just farm fires…

Generally, air quality deterioration is attributed to agricultural residue burning in October and November. Though it has a significant impact, it is not the only parameter that makes an impact. Vehicular emissions, wind-blown dust, and emissions from construction sites and other such factors that could be described as 'fugitive’ elements are among the major drivers of Delhi’s pollution scourge.

Different source apportionment studies assessed the contributions from different sources and have found out that meteorological conditions of the episode-based emissions varied from those during the festival season and from residual burning.

Every winter, New Delhi's Air Quality Index (AQI) becomes a central talking point amongst mainstream media, policymakers, and social media. However, the issue of toxic air goes beyond the administrative boundaries of Delhi-NCR and affects millions of people – especially those residing in the Indo-Gangetic Plain (IGP).

The Indo-Gangetic Plain is a land-locked region covering an area of about 700,000 square kilometres and is home to 480 million or 40 per cent of India’s population across five states and two union territories. The region's population density is more than three times that of the rest of the country (AQLI, 2019). It is also the epicentre of the country’s ambient air quality crisis, yet has received scant attention from state authorities.

The geographical expanse of the IGP, however, extends beyond India. It includes northern and eastern India, parts of Eastern Pakistan, Bangladesh, and southern Nepal. Combined with unregulated industrial growth, unfavourable topographical and meteorological conditions have exacerbated the health impacts of air pollution on its population. This issue of air pollution needs to be seen as a transboundary problem.

Complacency stymied pre-emption?

The imagery smog over Delhi of last few days looks something out of a science fiction nightmare. Until October, the media and government were busy celebrating clean days and improved environmental conditions. However, amid this period of self-congratulation, we failed to anticipate the looming disaster.

Long-term data consistently shows that the first half of November is among the worst for air quality. Yet, everyone was satisfied with the cleaner post-Diwali day and conveniently overlooked the critical role of meteorology in that outcome.

Then came reports of high pollution levels in neighbouring regions, including the news that AQI had crossed 1000 in some Pakistani cities. However, even these warnings failed to raise alarm. Suddenly, the wind direction shifted, placing us downwind of massive plumes of smoke, engulfing the capital city – and, more broadly, across the Indo-Gangetic Plain. Within hours, the Air Quality Index (AQI) soared from “very poor” to “severe-plus,” maxing out the scale.

This raises a crucial question: Where did our decision-making go wrong again?

The sources of pollution are known, data is available, forecasts are made, and meteorological patterns are well-documented. We have administrative machinery, inter-state and intra-state coordination agencies, and standard operating procedures. So why did the system fail to act in time to manage a predictable episode?

The issue stems from weak enforcement and poor coordination. Despite early warning signs, the Graded Response Action Plan (GRAP) was not implemented effectively. Although the Standard Operating Procedures (SoPs) clearly define the responsibilities of various stakeholders, delayed action led to the worsening of the situation. Even as conditions reached ‘severe’ levels, vehicle usage rationing (odd-even), which is part of GRAP Stage IV, was not considered for implemented despite its substantial potential to mitigate the impact.

On the other hand, it is a well-known fact that the delayed sowing in the North Western agricultural belt substantially contributes to the problem of Smog that blows into the Gangetic heartland and the national capital.

Farm residue burning, in fact, is largely seen as an outcome of the Preservation of Subsoil Water Act, 2009, which was brought in by the Punjab and Haryana governments to preserve groundwater. The legislation had, in effect, impacted the sowing and harvesting seasons for paddy and had a concomitant effect on the subsequent transition to the wheat sowing season by providing only a brief window which prompts the stubble burning phenomenon.

On the other hand, no significant review of this approach has been done, nor have significant steps been taken to provide sustainable alternatives for managing agricultural residue. While it is fair to question whether strict adherence to protocols can fully prevent pollution episodes influenced by meteorological conditions, there is no doubt that timely and consistent efforts could significantly reduce their severity.

An assortment of such policy shortcomings and implementation failures has left the commoner to bear the brunt of the crisis. Such episodes will remain a recurring nightmare until we address these enforcement and coordination gaps.