India’s winter air pollution crisis—most acutely experienced across Delhi and the National Capital region (Delhi-NCR), Northwest India, and the Indo-Gangetic Plain—has moved well beyond being a seasonal inconvenience. It has become a structural, recurring public health emergency. Each winter, Air Quality Index (AQI) levels routinely cross 400-500, entering the “severe” and “emergency” categories, where even short-term exposure poses serious health risks. This crisis is neither accidental nor unpredictable; it is the outcome of a persistent interaction between rising emission loads and unfavourable winter meteorology.
At the core of the problem lies a steadily increasing emissions baseline. Rapid urbanisation, construction activity, fossil-fuel–based power generation, industrial clusters, waste and biomass burning, and seasonal crop residue burning together load the regional atmosphere with pollutants well before winter sets in. Transport remains a major urban contributor, but its role is often oversimplified. Delhi today has over 12 million registered vehicles, nearly 70 per cent of which are two-wheelers. Historically, two- and three-wheelers contributed disproportionately to hydrocarbon and nitrogen oxide emissions due to the dominance of two-stroke engines and weak emission standards. However, this emissions profile has evolved significantly over the past decade.
The phased implementation of Bharat Stage emission standards—culminating in BS-VI norms in 2020—has led to a substantial reduction in per-vehicle emissions. BS-VI standards mandate ultra-low sulphur fuels (10 ppm), advanced after-treatment systems, improved combustion efficiency, and on-board diagnostics, resulting in sharp declines in particulate matter, sulphur dioxide, and nitrogen oxides from new vehicles. Consequently, newer internal combustion two-wheelers are significantly cleaner than earlier generations. Today, a disproportionate share of transport-related pollution arises from legacy vehicles—pre-BS-IV and BS-III models—that continue to operate due to slow fleet turnover and weak scrappage enforcement.
Alongside cleaner combustion technologies, electric mobility has begun to reshape the transport emissions landscape. Delhi and several other Indian cities now report electric two-wheelers accounting for over 10 per cent of new registrations, among the highest adoption rates nationally. Electric two- and three-wheelers offer zero tailpipe emissions and are particularly well suited for dense urban environments. Yet, their impact on ambient air quality remains limited by scale. Rapid growth in vehicle ownership, rising travel demand, congestion-induced emissions, and the continued dominance of fossil-fuel electricity generation dilute the gains from electrification. More importantly, during winter, transport emissions are often overwhelmed by pollution from biomass and waste burning, coal-based power plants in the regional airshed, and agricultural residue burning, which elevate background pollution levels before meteorological trapping takes effect.
Meteorology is the critical amplifier. During winter months, calm winds, frequent temperature inversions, high relative humidity, and a shallow atmospheric mixing layer prevent both horizontal and vertical dispersion of pollutants. Emissions that might otherwise dilute instead accumulate rapidly near the surface. This phenomenon affects not just Delhi but the entire Indo-Gangetic Plain, exposing nearly 400 million people to prolonged periods of hazardous air quality. The crisis, therefore, is not local but regional in scale, demanding coordinated airshed-based governance rather than city-centric firefighting.
History offers a sobering parallel. In December 1952, London experienced the Great Smog, caused by extensive coal burning combined with anticyclonic conditions, calm winds, temperature inversion, and high humidity. In just four days, an estimated 12,000 excess deaths occurred, and more than 100,000 people fell seriously ill. The episode fundamentally altered global understanding of the relationship between air pollution and human health. Political pressure forced decisive action, culminating in the UK Clean Air Act of 1956 and a long-term shift away from coal, supported by strict enforcement. British cities never returned to those pollution levels.
Delhi-NCR today mirrors many of these conditions: high emissions, adverse meteorology, dense population exposure, and limited adaptive capacity. While India has no shortage of policies—ranging from National Green Tribunal directives on stubble burning to central schemes allocating over Rs 1,100 crore for in situ crop residue management—their implementation has been fragmented and inconsistent. Emergency measures such as traffic rationing, construction bans, and school closures offer visibility but fail to address the structural drivers of pollution. The result is an annual cycle of crisis response rather than sustained prevention.
International experience demonstrates that transformation is possible. Beijing, which faced pollution levels comparable to or worse than Delhi’s prior to 2013, reduced PM2.5 concentrations by over 40 per cent within a decade through legally binding targets, strict enforcement, energy transition, industrial relocation, and coordinated governance. India, by contrast, continues without a comprehensive, parliamentary Clean Air Act that establishes enforceable standards, clear accountability, and long-term policy coherence across sectors and states.
The public health costs of delay are enormous. Air pollution is among India’s leading risk factors for premature mortality, contributing to millions of lost life-years annually, alongside rising healthcare expenditure and productivity losses. Expecting sustained public pressure for clean air in a context of economic precarity and limited adaptive capacity is unrealistic. The responsibility for action must therefore rest squarely with the state.
History’s lesson is unambiguous: when air pollution reaches crisis proportions, incrementalism fails. The London smog of 1952 catalysed systemic reform because the costs of inaction became undeniable. India stands at a similar inflection point today. A strong, legally binding Clean Air Act—grounded in science, insulated from vested interests, and implemented with long-term vision—is no longer optional. Hence, clean air act by the central government in the next parliament session with relatable action like (NGT)’s action for Beas Kund in the Rohtang area should be drawn up.
Clean air is not a luxury or an environmental ideal; it is a foundational precondition for public health, economic resilience, and sustainable development. Normalising toxic winters is, ultimately, a choice—and a human-made one.
Ashish Mansharamani is the Associate Director at Indian Social Responsibility Network
Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth