Children stand by the side of the street on their way to school. Source: Thomas Schoch.

Which of our world’s cities has the worst air pollution? According to the World Health Organization, it’s Delhi, the capital of India.1 Although air pollution affects the entire population of this metropolis, Delhi’s children are the most defenseless against its toxic effects. Recent studies have confirmed serious deterioration of air quality in Delhi, as well as other major cities across India. Air pollutants such as sulfates, nitrates, and black carbon force their way into the developing lungs and cardiovascular systems of children, resulting in decreased quality of life and increased mortality rates.1 Air quality has deteriorated to such an extent that one of India’s top pollution researchers, Sarath Guttinkinda, has stated, “If you have the option to live elsewhere, you should not raise children in Delhi.”2 He has since moved his family out of Delhi to protect his two young children.

On September 27, 2016, The World Health Organization (WHO), an agency of the United Nations that focuses on international public health, released a new air quality model revealing that 92% of the world’s population lives in places where air pollution levels are greater than WHO-recommended limits.3 The report indicated that over 3 million premature deaths around the world each year are associated with exposure to outdoor air pollution. India has the world’s highest mortality rate from respiratory disease, with 159 deaths per 100,000 in 2012, about twice that of China’s.4 Delhi’s air is more than two times as polluted as Beijing’s, which has the highest rate.2 And while the smog in China’s major cities get most of the world’s attention, six of the ten most polluted cities in the world are in India.5 In addition to Delhi, the other highly polluted Indian cities are Gwalior, Allahbad, Patna, Raipur, and Ludhiana.6 Air pollution in India is ten times the WHO’s recommended maximum, twelve times the standards employed in the United States, and over twice the level considered acceptable by the Indian government.7 Flavia Bustreo, WHO assistant director general, stated, “When dirty air blankets our cities the most vulnerable urban populations, -the youngest, oldest and poorest- are the most impacted.”1

Air pollution refers to the adulteration of the earth’s atmosphere with particles that compromise human health, quality of life or the natural functioning of the ecosystem.8 Air quality is generally measured by looking at exposure to tiny particulates smaller than 2.5 microns, known as PM2.5s, which penetrate the lungs. The PM2.5 standard includes particles with a diameter of no more than 0.0002 inches or one-seventh the width of a human hair.1 The recently released WHO urban database reports that Delhi has exceeded the maximum PM2.5 limit by almost ten times.8 Only two other cities in the world, Ludhiana and Kanpur, exceed Delhi’s levels. Notably, these cities are also located in India. In fact, air pollution is now the fifth largest killer in India, according to a 2010 report of the Global Burden of Disease (GBD), which tracks illnesses and deaths worldwide.9 About 620,000 premature deaths occurred in India from diseases related to air pollution in 2010, a six-fold increase from 100,000 deaths in 2000.10 49% of these deaths were caused by heart disease, 25% by stroke, 17% by chronic obstructive pulmonary disease, 7% by lower respiratory infections, and 2% by trachea, bronchus and lung cancer.9

Scientific studies on the effects of air pollution on children in India conclude with certainty that for many, their health will be compromised for the rest of their lives. An extensive three-year study that was published in 2010 and was conducted by the Kolkata-based Chittaranjan National Cancer Institute (CNCI) in conjunction with WHO found that key indicators of respiratory health, lung function, blood pressure in children in Delhi between four and seventeen years of age were far worse than those of children elsewhere. The tests were conducted on a total of 11,628 school-age children from 36 schools throughout Delhi and 15 rural schools in West Bengal and Uttaranchal.11 Specific findings from lung tests show that 43.5% of the Delhi school children suffered from “poor or restrictive lungs,” as compared to 22% of the kids in the rural schools.12 Alveolar macrophages (AM), lung cells that clean off microorganisms and dust particles, were 2-3 times more frequent in Delhi school children than in rural children. This high AM number indicated that the Delhi children had greater exposure to particulate pollution, as AM represents the first line of cellular defense against inhaled pollutants.11 Additionally, about 15% of the children in Delhi reported frequent eye irritation (vs. 4% of rural children), 27.4% reported frequent headaches (vs. 12% rural), 11.2% experienced nausea (vs. 5% rural), 7.2% reported heart palpitations (vs. 3.3% rural) and 12.9% were fatigued (vs. 6.7% rural).13 The report concluded that about half of the 4.4 million children who reside in Delhi already have irreversible lung damage.12

Delhi’s poorest children are the most vulnerable and bear the most burden of the city’s poor air quality. There is an inverse relationship between socioeconomic status and the pervasiveness of lung function deficits: the lower the socioeconomic status, the greater the percentage of children with reduced lung function.11 According to WHO’s 2016 urban air quality database, 98% of cities in low-and middle-income countries with a population greater than 100,000 do not meet WHO air quality standards. However, in high-income countries, this percentage is a much lower 56%.4

Crowded streets and everyday tra c in the city of Delhi. Source: TrekEarth.

The rapid deterioration in air quality in cities like Delhi is the result of a combination of exploding populations and the lack of stringent government regulations to control smog and soot from rapidly growing industry, transport, and construction.1 Anumita Choudhury of the Centre for Science and Environment, a Delhi thinktank, says part of the problem, “is a mobility crisis as use of private vehicles has soared while public transportation has suffered chronic under-investment.”7 Between 1991 and 2011, Delhi’s population more than doubled to 22 million, and the number of cars increased five times to about 8 million, at a rate of half a million new cars per year.10 Another major contributor to air pollution in Delhi is the presence of the 70,000 trucks that drive directly through the city on long distance journeys. The government is aware of this issue but its plan to build a bypass has been delayed year after year.7 In the meantime, there is a very young poor population currently being exposed to this severe roadside pollution. Many children walk to school along busy roads, receiving extremely high doses of toxic chemicals and damaging particulates. The daily levels of toxic air in Delhi schools, which are often close to roads, are more than ten times worse than acceptable, according to the WHO.7

Dr. Sanjeev Bagai, a Delhi pediatrician, stated that the number of children he has treated who have been impacted by air pollution has more than doubled in the last ten years. He said children of all age groups are vulnerable and “even newborns have respiratory diseases, which were previously not seen so early in life.”10 The WHO has found that children are most susceptible to the harmful effects of air pollution for a number of reasons. Children spend more time outdoors than adults, and are outdoors during the middle of the day when air pollution levels are higher.11 Children’s bodies also demand significantly higher oxygen levels so their respiration rates are higher and they inhale more air per unit of body weight than adults do. Additionally, because of children’s small stature, their breathing zone is closer to the ground where the most polluted air is. This means they are continually inhaling air loaded with the most particles.14 Further, the diameters of the alveoli in their airways are narrower, which makes them more easily affected by inflammation caused by air pollution.11 Children’s lungs are still developing and their immune defense is immature so, as a result, they are more vulnerable to toxic pollutants.15 The WHO concludes that exposure to toxic air during childhood reduces lung growth and the adult-maximum functional lung capacity, which can result in increased susceptibility to infection and pulmonary and vascular diseases, even past adolescence.14 The WHO also concludes that polluted air affects development of the nervous system in children, potentially reducing cognitive function.15

Delhi has taken small steps to reduce the level of air pollution. One such step includes the banning of large diesel cars from the center of Delhi.1 However, Anumita Roychowdhury, executive director at the Delhi based Center of Science and Environment (CSE), believes that in order to reduce air pollution to WHO standards, environmental policy needs a thorough overhaul.5 The CSE and the Central Pollution Control Board (CPCB) have made short term and long-term recommendations to India’s government that include the following:

  • Make the National Ambient Air Quality Standards legally binding in all Indian cities and impose penalties on cities that violate them.9
  • Regularly monitor PM air pollutants. Each day the public must receive specific health advisories and emergency smog/pollution alerts.11
  • Control and cut increases in the total number of vehicles by increasing public transportation, utilizing non-motorized transport and compact city planning and restraining the use of cars.9 Battery-driven vehicles should be employed and mass transit should be promoted. Carpools, pedestrian walkways and bicycles should be encouraged through the redesigning and development of communities.11
  • Prevent children’s exposure to diesel exhaust, which contains toxic fine particulates. School buses that use diesel should be eliminated and a cleaner fuel should be implemented.11 Where possible, relocate schools and child care facilities to areas that are at walking distance from children’s houses and away from roads with heavy traffic or other sources of air pollution. Further, offices and shops should relocate closer to residential areas.
  • Mandate annual lung function tests and blood pressure tests performed in medical facilities set up at schools for all children ages nine and over in Delhi. These medical facilities should contain all the necessary equipment as well as trained technicians.11
  • Reduce industrial smoke stack emissions and increase the use of renewable power sources like solar and wind.1
Source: Wikimedia Commons.

Roychowdhury says, “There is hard evidence now to act urgently to reduce the public health risk to all, particularly children….India will have to take aggressive action to reverse the trend of short-term respiratory and cardiac effects as well as long-term cancer and other metabolic and cellular effects.”9 Encouraging news from WHO data indicates that cities that commit to reducing air pollution are having successes. More than one third of the cities in low-and middle-income countries that made the commitment were able to reduce their air pollution levels by more than 5% in the last five years.1 Delhi and all other cities in India need to take action now to reduce air pollution and save both the environment and the long-term health of their people.

Rebecca Slutsky is a junior in Silliman College majoring in Molecular, Cellular & Developmental Biology. She can be contacted at



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