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As winter sets in, a dense layer of toxic smog has descended over Delhi, driving the city’s air quality down to its worst level in eight years. Air pollution levels have deteriorated rapidly since the end of October, remaining hazardous every day since November 12. On November 18, the Air Quality Index (AQI) hit 494, plunging the city’s pollution levels into the “severe plus” category, the worst classification possible. Anything up to 50 is deemed “good”; beyond 200 is “poor.”
This smog, composed mainly of fine particulate matter, known as PM2.5, has engulfed what was already the most polluted city in the world, leaving residents struggling with burning eyes, itchy throats, persistent coughs, fever, and breathing difficulties. PM2.5 are fine particles that penetrate the lungs and bloodstream, increasing the risk of respiratory diseases and cardiovascular problems. Exposure in children has been linked to impaired lung development, reduced brain volume, and ADHD.
On November 18, the pollution-monitoring company IQAir recorded Delhi’s PM2.5 levels at more than 60 times the safety limit recommended by the World Health Organization. It’s a bad spike, but air quality shouldn’t be seen as just a winter problem, says Avinash Chanchal, Greenpeace South Asia’s deputy program director. Year round “we are observing a very high level of pollutants,” he says. “Two times, three times, four times, five times higher than the national ambient air quality standards.”
Stagnant weather conditions across the whole of northern India and Pakistan are largely responsible for conditions being so bad right now, trapping pollutants over the region. But pollution itself is also surging, thanks to farmers clearing their fields with fire at the end of the growing season, more fires being lit for heating and cooking, and smoke from fireworks, which have combined with Delhi’s year-round mix of industrial emissions and vehicle pollution.
In response to this crisis, city authorities are turning to tech: Delhi’s Winter Action Plan, introduced in September, proposes using technological innovations to fight pollution. Interventions include drone monitoring, artificial rain, an anti-dust campaign, and mobile anti-smog guns. But these have been criticized as unproven strategies that offer only short-term relief without tackling the systemic causes of pollution.
In late November, Delhi’s environment minister Gopal Rai sought permission from the central government to use cloud seeding to produce artificial rain to break the smog layer and reduce air pollution. The same proposal was made last year, but was not carried out due to unfavorable weather conditions.
Cloud seeding, a weather-modification technique that involves injecting chemicals such as salt or silver iodide into clouds to induce rain—different chemicals are used in different climates—could help wash pollutants from the air, though there are limitations. “It depends on ideal conditions—specific levels of humidity, precipitation, and cloud properties,” says Manoj Kumar, an air pollution analyst at the Finland-based think tank the Centre for Research on Energy and Clean Air. “Even if it works, there’s no guarantee the rain will fall where it’s needed. It could end up raining in parts of Uttar Pradesh instead of Delhi.”
The process is also expensive, costing an estimated 130 million rupees ($1.5 million) in return for what would only be a short period of relief if successful. “Even if the rain clears the air temporarily, pollution will quickly return due to traffic, industrial emissions, and meteorological conditions. It’s addressing the problem at the endpoint, not the source,” Kumar says.
Data from the Indian Institute of Tropical Meteorology’s Decision Support System also shows that around 30 percent of Delhi’s air pollution comes from local sources. The rest drifts in from neighboring states—meaning local solutions such as cloud seeding are likely to be largely ineffective. “There’s no pilot project to show how effective it might be or what percentage of pollution it could reduce,” Kumar says.
In November, the Delhi government also ran a pilot project for drone-based mist spraying in Anand Vihar, one of the city’s pollution hotspots. These drones, each carrying 15 liters of water, are used to spray mist along roads to suppress fine dust, which can be another form of PM2.5.
Mohan P. George, consultant scientist at the Indian research body the Centre of Science and Environment and the former head of the Delhi Pollution Control Committee’s air quality division, has concerns about the practicality of dust-suppression techniques like water sprinkling. While these measures may help reduce visible dust in the air, he claims, they don’t address the sources.
“Dust suppression is used in mining areas where there is heavy vehicle movement and poorly surfaced roads,” says Karthik Ganesan, senior researcher of the Delhi-based think tank Council on Energy, Environment, and Water. “It’s not a solution for citywide air pollution control, especially in all of Delhi’s roads, where the real problem is vehicular emissions, industrial pollution, and construction waste,” Ganesan says.
Indeed, the largest source of air pollution in Delhi are vehicle tailpipes. Greenpeace’s Chanchal suggests that to bring down air pollution, the government should instead be focusing on a better-integrated, more efficient public transport system that’s affordable and accessible. “If you subsidize public transport, it would reduce reliance on cars,” he says. “We need permanent solutions like these.”
Such long-term solutions might not be here yet, but the Delhi government is taking some steps to try to tackle pollution at source. In response to November’s pollution spike, it invoked stage four of its Graded Response Action Plan (GRAP). These emergency measures include halting construction and demolition activities, banning the entry of trucks into Delhi, and closing schools to reduce emissions. Stage four measures, applied when the city’s air pollution is classified as “severe plus,” also bans diesel and petrol vehicles from other states from entering Delhi.
But despite the promise of these tactics, the smog is expected to persist throughout the winter. India’s Supreme Court says there have been delays in enforcing the stage four measures, and has blamed both the Delhi government and the Commission for Air Quality Management (CAQM), the central government’s monitoring agency, for these. Experts believe that while GRAP is necessary for emergencies, its implementation has been inconsistent and poorly tracked. The CAQM did not immediately respond to a request for comment.
Kumar says that since the commission took over managing the plan back in 2021—at which point there was also an overhaul of its measures—the plan has had little impact on PM2.5 levels during peak pollution months. “The measures exist on paper, but the lack of enforcement makes them ineffective.” Part of the problem, he argues, is that while vehicle emissions are important to look at, GRAP measures are not doing enough to curb other key sources of pollution—“tackling industries and thermal power plants—major contributors of particulate matter and sulfur dioxide.”
There’s also not enough being done to evaluate what’s working and what isn’t, Kumar says. “When we restrict vehicle emissions, we need mechanisms to measure how much pollution has been reduced. The lack of transparency and accountability undermines these efforts.”
The Delhi government’s real-time pollution-source monitoring supersite, R-AASMAN, has been inactive since November last year. Without reliable data, enforcing policies becomes even more difficult. Better calibration and maintenance of monitoring equipment is also needed, says Kumar. “We need to ensure that air quality monitors are placed away from obstructions, and regularly calibrated as per Central Pollution Control Board criteria to get reliable data for air quality management.”
Amid all of these concerns, the city has been turning to drones to monitor pollution hotspots, in addition to those spraying water to suppress PM2.5. “Drones are useful for accessing areas that are hard to monitor manually, like crowded urban zones or industrial regions,” says R Subramanian, air quality head at the Center for Study of Science, Technology, and Policy, a think tank based in Bangalore. However, while these can identify pollution sources, follow-up inspections and actions are necessary to resolve issues. “Local officers need to observe and enforce changes, such as rerouting traffic or shutting down specific polluting activities,” he explains.
Subramanian also stresses the importance of expanding pollution forecasts. “Delhi uses SAFAR, an air quality dashboard run by the Indian Institute of Tropical Meteorology, which provides three-day forecasts combining computational models and machine learning. But, extending this forecasting capability to 10 days would give authorities more time to implement preemptive measures,” he says.
Even if Delhi’s muddle of pollution-control techniques can be refined and made effective—and there’s a lot of work needed to achieve this—this doesn’t address the fact that air pollution is part of a much larger regional problem, as recent satellite images from NASA show. A thick smog blanket is currently covering the entire Indo-Gangetic Plain, stretching across northern India and Pakistan. Pollution affects the entire airshed of the plain, a region where air flows and accumulates, moving across state and national borders, transcending political boundaries. “Efforts to address it must go beyond Delhi,” says Kumar.
Sagnik Dey, a professor at the Centre for Atmospheric Sciences at the Indian Institute of Technology in Delhi, says that satellite data is working to shift the focus from city-centered solutions towards a regional approach, which is reflected in India’s National Clean Air Programme. “We can now track pollution across entire airsheds, showing that rural areas, particularly in the Indo-Gangetic Plain, are just as polluted, if not more so, due to biomass burning,” Dey says.
Satellite monitoring could go further, Subramanian suggests. He’d like to see it used to track methane emissions from industrial facilities to identify super emitters, as well as on-the-ground remote sensing of vehicles to assess tailpipe emissions and identify faulty vehicles that need repairing or scrapping. These interventions could support wider evidence-based policy decisions, he claims.
“We cannot solve Delhi’s pollution problem just by focusing on the city,” Dey adds. “It requires collaboration across national ministries, central and state governments, and local authorities.” However, while data is crucial for tracking progress, Dey highlights that solving the problem requires action from regulatory agencies. There is a big gap between the National Clean Air Programme’s work and what needs to be done.
Despite advancements in pollution-control technologies, Delhi’s air quality is unlikely to improve significantly in the next decade without decisive political action, experts believe. Rising energy demands, urbanization, and industrial growth will only add to the burden if heavily polluting sectors like thermal power, steel, and transport remain poorly regulated. “We already have enough science, data, and solutions,” says Chanchal. “What we need is the political will to implement them.”
