For decades, lung disease in India was largely framed as a smoker’s problem. That assumption no longer holds. A growing body of evidence now points to a more unsettling reality that even people who have never touched a cigarette are increasingly developing chronic respiratory and cardiovascular illnesses driven largely by the air they breathe.
Mumbai’s winter air offers a stark illustration. Despite marginal improvements in overall Air Quality Index (AQI) readings this season compared to previous years, particulate pollution, especially PM2.5, has remained persistently high across several parts of the city.
Health experts warn that this fine particulate matter, invisible to the naked eye, is quietly eroding lung health, triggering heart disease, and raising stroke risk, even among non-smokers.
What does PM2.5 mean?
PM2.5 refers to airborne particles that are 2.5 microns or smaller. These are tiny enough to bypass the body’s natural defence mechanisms. Unlike larger pollutants that get trapped in the nose or throat, PM2.5 penetrates deep into the lungs and can enter the bloodstream. Once there, it contributes to systemic inflammation, long-term lung damage, and cardiovascular stress.
What makes PM2.5 particularly dangerous is the absence of a known 'safe' threshold. While Indian air quality standards and global guidelines prescribe acceptable limits, health researchers increasingly argue that even levels within these limits can be harmful over prolonged exposure.
In urban India, PM2.5 comes from a toxic mix of vehicular emissions, construction dust, industrial activity, waste burning, and secondary pollutants formed through chemical reactions in the atmosphere. Winter worsens the problem, as cooler temperatures and low wind speeds trap pollutants closer to the ground.
One of the biggest challenges in public understanding is the way AQI is interpreted. A 'moderate' or even 'satisfactory' AQI day does not necessarily mean the air is safe. AQI is a composite index, calculated using multiple pollutants, and the final number is driven by whichever pollutant is dominant on a given day.
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This means that PM2.5, which is widely considered the most harmful air pollutant, may not always be the primary contributor to AQI, even when its concentration remains high. As a result, people may underestimate health risks simply because the AQI colour code looks reassuring.
Public health experts tell THE WEEK that PM2.5 deserves to be looked at independently, not just as one component of AQI, especially when assessing long-term health outcomes.
Pulmonologists across India are seeing a worrying trend of rising cases of chronic obstructive pulmonary disease (COPD), asthma, reduced lung capacity, and even lung cancer in non-smokers. Long-term exposure to polluted air is now recognised as a major risk factor.
The irony is cruel. While smokers knowingly inhale toxins, non-smokers have little choice. Daily commuting, outdoor work, school runs, and even time spent indoors, where outdoor pollution seeps in, become sources of exposure. Children, the elderly, pregnant women, and those with pre-existing conditions are particularly vulnerable, say doctors.
Air pollution also extends its damage beyond the lungs. Studies increasingly link PM2.5 exposure to heart disease, irregular heart rhythms, hypertension, stroke, metabolic disorders, and adverse pregnancy outcomes.
India’s national air quality standards for PM2.5 remain significantly more lenient than those recommended by the World Health Organization (WHO). While the WHO has progressively tightened its guidelines in light of new evidence, implementation and enforcement in India lag.
Experts argue that regulatory thresholds must evolve to reflect current times because, without stricter limits and stronger enforcement, cities risk normalising chronic exposure to harmful air.
"Addressing PM2.5 pollution requires structural, not cosmetic, solutions. Incremental measures such as temporary construction bans or short-term traffic restrictions offer limited relief. What is needed instead is sustained action on cleaner transport, tighter industrial emissions control, waste management reforms, and urban planning that reduces dust and congestion," says Prakash Patel, who heads a citizens' group in South Mumbai that champions the cause of clean air.
Equally important is public communication. Activists insist that the BMC inform the citizens regularly that air pollution is not merely an environmental issue but a slow-burning health crisis and that we must go beyond these stop-gap measures of wearing masks on high-pollution days, using indoor air purifiers and limiting outdoor activity during peak pollution hours.
Perhaps the most unsettling takeaway from India’s air pollution crisis is that for millions of urban Indians, the simple act of breathing has become a health hazard. And until PM2.5 is treated with the urgency it demands, clean lungs may soon become a privilege rather than a right.