Air in India’s capital ranked world’s most polluted on eve of Diwali

An air-quality index, or AQI, summarizes the amount of air pollution using measured concentrations of pollutants. It helps people understand whether outdoor air is relatively safe or hazardous. Higher scores generally indicate greater pollution risk, but the number only makes sense within the system that produced it.

IQAir ranked Delhi using a US air-quality index reading based on pollutant concentrations. At 10.35am, its score was 581. India’s Central Pollution Control Board gave Delhi a score of 363 at 10am. The two readings came from different systems, with different scales and methodologies, so 581 is not simply a number that can be compared with 363.

Both readings showed serious pollution, despite their technical differences. India’s official score placed Delhi in the “very poor” category. Comparing the categories and methods, rather than subtracting the numbers, gives a more accurate picture. The difference also shows why AQI figures need their source and scale identified.

Delhi’s pollution was severe compared with Lahore’s on IQAir’s scale. At 10.35am, IQAir ranked Delhi first among the world’s major cities, with a US air-quality index reading of 581. Lahore, in neighbouring Pakistan, recorded 285, making Delhi’s reading more than twice as high.

India’s Central Pollution Control Board measured Delhi at 363 at 10am. That score was placed in India’s “very poor” category. The comparison needs care because IQAir’s score and India’s official score use different scales and methods. Delhi’s 581 and 363 therefore should not be treated as equivalent measurements.

Together, the figures show both international concern and a serious official assessment. The pollution occurred just before Diwali, when firecrackers could worsen conditions. Authorities ordered schools to offer online classes, encouraged working from home, and introduced temporary restrictions on construction, industry, and vehicles.

Diwali firecrackers add smoke and toxic gases to air that is already polluted. Their impact is collective: one household’s fireworks may affect a small area, but thousands of households celebrating at once can release emissions across many neighborhoods. The extra pollution matters because people nearby may breathe it even if they never set off fireworks.

The article describes Diwali as a festival celebrated by an estimated 1 billion people worldwide. When many households set off fireworks, their combined emissions can worsen air quality across neighborhoods and entire cities. In Delhi, this comes after pollution from traffic, factories, construction dust, and burning crop residues and waste has already accumulated.

The timing makes the problem worse. Diwali occurs before or during winter conditions that can hold pollution near the ground. Authorities issued warnings and restrictions, while public health experts urged people to avoid firecrackers. Electric lights offer a way to celebrate without adding the gases and smoke produced by fireworks.

Delhi’s pollution is not caused by Diwali alone. Across India, Pakistan, and other parts of South Asia, traffic, factories, construction dust, and burning crop residues and waste foul the air. These sources operate across different seasons and locations, creating a persistent regional pollution problem.

For example, vehicles release pollution as people travel, while factories emit pollution during production. Construction can add dust, and burning crop residues or waste adds smoke and particles. The article also notes that Delhi authorities temporarily restrict construction, industry, and vehicles, but experts say such steps often fail to address the root causes.

The year-round nature of the problem means short emergency measures cannot provide lasting protection. Delhi is promoting electric vehicles through a long-term plan. Public health experts call for sustained action on pollution sources and affordable healthcare, while individuals can reduce exposure with properly fitted masks and by avoiding strenuous outdoor exercise during heavy pollution.

Wind normally helps move and disperse pollution away from its source. When winds are weak, pollutants from traffic, factories, dust, and burning remain concentrated instead of being carried elsewhere. Stagnant air therefore allows pollution levels to rise in the same area.

Delhi’s winter conditions create this problem. The article says weak winds and stagnant winter air allow pollution to build up. That buildup can become especially dangerous near the ground, where people walk, work, exercise, and breathe. Early mornings can be particularly concerning, so Dr Arvind Kumar advised avoiding strenuous outdoor exercise then during heavy pollution.

This weather effect explains why pollution can become severe even without a single new source. Existing emissions continue entering the air while limited movement prevents them from dispersing. Short-term restrictions may reduce some emissions, but cleaner air requires sustained action on traffic, industry, construction dust, and burning.

Heavy air pollution can irritate the breathing system and harm wider health. Dr Arvind Kumar linked it to persistent coughing, inflamed airways, asthma-like attacks, pneumonia, heart attacks, and strokes. He also linked prolonged exposure with impaired lung development in children and lung cancer.

Children are especially vulnerable because their lungs are still developing, so prolonged exposure may impair that development. People with asthma can face triggered or worsened attacks when polluted air inflames the airways. Outdoor workers may be unable to avoid exposure because their livelihoods require them to remain outside, even during dangerous pollution episodes.

The article recommends properly fitted N95 or N99 masks outdoors, avoiding strenuous exercise, and taking care during heavy pollution. However, personal precautions have limits. Outdoor workers cannot simply stay home, and many families cannot afford air purifiers. Lasting protection requires governments to reduce pollution and provide affordable healthcare.

Fine particulate pollutants such as PM2.5 are tiny airborne particles about 2.5 micrometers wide or smaller. Their small size allows them to travel deep into the lungs. The supplied article discusses air pollutants and health effects but does not specifically define PM2.5 or explain its biological pathway, so this particle-size definition and mechanism come from established health knowledge.

Once inhaled, fine particles can irritate lung tissue and drive inflammation. Some particles or their effects can enter the bloodstream, strain the cardiovascular system, and increase risks involving the heart and brain. The article links pollution with heart attacks and strokes, and says prolonged exposure can impair children’s lung development. These effects make particle pollution more than a breathing problem.

Children face concern because their lungs are developing. People with asthma may experience inflamed airways and attacks. Reducing exposure requires cleaner air, not only personal protection. The article recommends fitted N95 or N99 masks and avoiding heavy outdoor exertion, while calling for governments to address pollution sources.