How air pollution is causing greater loss of healthy life years in children compared to older people

The toxic journey starts from the womb. When mothers are exposed to polluted air during pregnancy, the foetus is at serious risk. The risk blows up as a massive disease burden for infants, children and adolescents, and lasts a lifetime. The problem has reached scary proportions in the Global South, with India bearing the infamy of accounting for a quarter of the global infant deaths—within a month of birth.

Mounting local and global evidence and well-decoded science define the biological pathways through which pollutants enter bodies and mutate organs. These estimates consider not just lower-respiratory infections affecting children but also a much broader set of health impacts. And children of poorer households are more at risk.

Foetuses exposed to toxins in the womb may have lower chances of survival. Exposure to toxin also leads to still-birth, preterm birth and low birthweight. It predisposes foetuses to a range of diseases later in life, including endocrine and metabolic disorders and diabetes. If air pollution affects the mother’s respiratory health, oxygen and nutrient delivery to the foetus can be reduced. Impaired lung development in utero increases the risk of airway diseases. Scientists explain that particulate matter can cause maternal inflammatory response, reduce maternal immunity and increase the risk of infection and poor neurological development. Babies born too small are more vulnerable and cannot cope with the risk of lower-respiratory infections, diarrhoeal diseases, brain damage and inflammation, blood disorders and jaundice.

In children under the age of five years, exposures to polluted air pose grievous risks. It affects brain and neurological development, lung function and can cause obesity. Neurological disorders include attention deficit hyperactivity, lower intelligence and impaired neurodevelopment. Even at a lower level of exposure children can develop lasting deficits in lung function, making them vulnerable to chronic lung disease in adulthood, affecting their quality of life.

Poor understanding of this evidence breeds policy complacency and scepticism. Powerful evidence is also mounting on infant deaths, acute respiratory infection, stunting, childhood anaemia, allergic rhinitis and neurodevelopmental outcomes. Cohort groups of mothers and babies have been tracked to find link between exposure during pregnancy and low birthweight in households that use solid fuels for cooking.

Air pollution and its impacts on children are gravest violations of their right to a liveable and viable future. This needs to be recognised. The National Clean Air Programme (NCAP) has to integrate exposure-based health evidence for multi-sector action. It has to ensure and monitor deep cuts in exposures from key sources of pollution in all situations, while improving ambient air quality and reducing children’s disease burden.

Declaring pollution holidays in schools during winter smog episodes is not the answer. The need is to ensure clean fuels to all households and industry, zero-emissions vehicles, reduced dependence on cars, and a circular economy to close the loop around waste streams to stop burning. Health adaptation plans in states and disease surveillance that the Union Ministry of Health and Family Welfare has initiated need to get stronger to inform NCAP. Clean air policy has an obligation to protect children from the toxic risk.

Airborne threat

On November 3, as night descended over Delhi, hundreds of children, coughing and gasping, thronged the out-patient department and emergency ward of Chacha Nehru Bal Chikitsalaya. Soon, the super specialty paediatric government hospital in east Delhi ran out of nebulisers and beds. Doctors at the hospital had been dreading the prospect since the last week of October, when the average air quality in the national capital remained in “very poor” category for six consecutive days before plummeting to “severe” category on November 3, with the air quality index (AQI) value reaching a staggering/hazardous 468. AQI values over 100 are considered unhealthy.

Doctors in the national capital and in adjoining areas are familiar with this seasonal plague. As the region chokes on dust and smoke in winter every year, hospitals receive an exceptionally large number of patients with respiratory problems.

In the first two weeks of November, when the capital city’s air quality remained mostly in the “severe” category, Down To Earth visited all the major hospitals to assess the impact on people’s health. Ajay Shukla, director and medical super-intendent of Atal Bihari Vajpayee Institute of Medical Sciences and Dr Ram Manohar Lohia (ABVIMS-RML) Hospital, one of the country’s premier hospitals run by the Union government, says the hospital records a 30 per cent rise in respiratory-related illnesses during severe pollution days. On November 6, ABVIMS-RML opened a dedicated weekly Pollution Out-Patient Department, a first-of-its-kind in the country, to cater to patients suffering from the impact of unhealthy air. Shukla says the initiative is to ensure that all the pollution-related cases—from cough to eye infection to headache—can be seen by the doctors of different departments at one place. In Vallabhbhai Patel Chest Institute (VPCI), another prominent hospital in north Delhi, hospital staff share a worrying data: between November 2 and November 10, the hospital on average received 50 new cases of respiratory illnesses on a daily basis.

What’s perturbing is that most patients visiting the hospitals with respiratory ailments are under 14 years. Ambavasan A, a senior resident doctor at the emergency ward of ABVIMS-RML, says the hospital is flooded with children with respiratory problems, and their number and severity of the condition varies as per the pollution level. Medha Mittal, endocrinologist at Chacha Nehru Bal Chikitsalaya, says, “Delhi’s air pollution is resulting in a rapid increase in respiratory illnesses among children.”

On November 2, when DTE visited Chacha Nehru Bal Chikitsalaya, three-year-old Vishal Prajapati lay still on a bed in a crowded emergency ward. “We hospitalised him a week ago, after he developed symptoms of pneumonia, with high fever, severe bouts of cough, shortness of breath and weakness,” Vishal’s mother tells DTE. “Since his birth, he develops respiratory problems as soon as the air pollution flares up, and has to be rushed to the hospital,” she adds.

One of the adjacent beds was shared by three children, each with a nebuliser mask covering the nose and mouth to directly deliver medication to the lungs to relieve congestion and treat respiratory infections. One of them was 10-month-old Yuven Thakur, who was for the first time visiting the hospital because of respiratory difficulties. “Doctors say that my son has upper respiratory tract infection and severe air pollution is responsible for his condition,” says Yuven’s father Dipanshu Thakur.

“Children in the age group of two to five years are the worst victims of air pollution,” says Sanjeev Bagai, paediatrician and nephrologist in Delhi. “The proportion of children visiting the hospital with respiratory problems has increased since mid-October. Those who already have respiratory problems (for instance, asthma and bronchiectasis) have developed worsening of symptoms despite regular treatment,” S K Kabra, head of the paediatric department, All India Institute of Medical Sciences (AIIMS), Delhi, tells DTE.

Breathless from start

There are reasons children are more vulnerable to air pollution than adults. Since the respiratory system is not completely developed in children, particularly in newborns and infants, they breathe faster than adults to ensure adequate provision of oxygen into the blood. Children also have high metabolic rate—the rate at which they use up energy—and therefore have a higher oxygen demand, which in turn results in higher respiratory rate than adults. Studies estimate that children typically breathe 40 times in a minute, which is more than double the respiratory rate of adults. “As they breathe more air per body size and have smaller airways than adults, they are at an increased risk of developing respiratory diseases and exacerbation of asthma,” states a study by researchers from Germany and the Czech Republic, published in Urban Climate on June 4, 2022.

Of the many air pollutants that children breathe, the dreaded ones are fine inhalable particles (particulate matter with diameter less than 2.5 micrometers or PM2.5) that originate from different local combustion sources such as vehicles, industries and burning of waste, and are laced with toxins. Since these particles are smaller than the red blood cells, studies have established that they can go deep into the lungs, escape to the bloodstream and also breach the blood-brain barrier, with hundreds of known and unknown health effects (more on this later).

The German and Czech Republic researchers examined the potential differences of PM2.5 exposure between children and adults in an urban area and found that the concentration of PM2.5 decreases with increasing height above ground. Since the breath levels of children are closer to pollutants emitted near ground, it makes them more vulnerable to emissions by traffic-related exhausts and whirled up fine particles.

Arvind Kumar, chairperson of Institute for Chest Surgery-Chest Onco Surgery and Lung Transplantation, Medanta, Gurugram, and Founder of Lung Care Foundation, shares a few photographs of lungs with DTE to show the impact of air pollution on respiratory health of those living in areas with poor air quality. “Healthy lungs look absolutely pink. However, we regularly see black deposits in the lungs of most non-smoker adults and children up to 14 years of age who come to us with respiratory illnesses. These black deposits cannot be removed and eventually damage the lungs,” says Kumar, adding that children are inhaling more toxic air than adults.

A public health emergency

The trouble is not confined to Delhi. Doctors point to a steep rise in respiratory illnesses among children across the Indo-Gangetic region, where air quality remains in the “poor” category almost throughout the year.

Air quality analysis of the past one year by Pune-based climate technology firm Respirer Living Sciences Pvt Ltd shows that the Indo-Gangetic region has seven of the 10 most polluted cities in the country. In 2018, non-profit Climate Agenda studied 14 districts of Uttar Pradesh and found that small cities like Gorakhpur and Mau are more polluted than the national capital Delhi and state capital Lucknow. Air pollution plagues rural areas as well and the entire state is under a “health emergency”, states the report, titled “Air Kills”. An analysis of Bihar’s air quality in the winter season, from October 2022 to February 2023, by Delhi-based research and advocacy institution Centre for Science and Environment (CSE) shows that the PM2.5 levels in at least 10 towns in the state were substantially worse than that of Delhi.

This is alarming. According to the Census of India, 2011, the Indo-Gangetic states—Punjab, Haryana, National Capital Territory of Delhi, Uttar Pradesh, West Bengal, Assam and Bihar—are home to almost half of the children (in the age group of 0-14 years) in the country and two-thirds of under-five children who are most vulnerable to air pollution.

Mohan P George, scientist with CSE, says, “In the Indo-Gangetic region, a month-old infant with a weight of 4 kg and breathing 40 cycles a minute will inhale 184 microgram of PM2.5 a day.” George’s calculation is based on the annual average of 100 microgram of PM2.5 level in the region’s air.

The impact is palpable. At a national conference, organised by the Indian Academy of Paediatrics in Kolkata in early November, pulmonologists pointed out that one in every two children in the metropolitan city suffers from respiratory disorders triggered by air pollution. “I treat children in northern fringe of city and can safely vouch that the number of patients has increased several times in the past few decades, though the actual impact, both long- and short- term, is difficult to be spelt out due to inadequate data,” says Subhamoy Mukherjee, a paediatric practising in Kolkata for more than three decades.

Arup Halder, another pulmonologist in Kolkata, says that first-generation asthma patients among children are on the rise. “Earlier, asthma patients usually had a family history of the condition, but now a sizeable number of children seem to be developing asthma because of exposure to air pollution. The problem increases especially in the winter when the air quality worsens,” says Halder. He suggests that the schools with morning shifts should start a little late because children get exposed to maximum pollution during that period.

In Bihar, there have been widespread reports of children suffering from respiratory infections, breathlessness and allergies, particularly during the winter months when the air quality hits the lowest points. Athar Ansari, professor, paediatric department at Nalanda Medical College and Hospital, a state government-run hospital in Patna, says that roughly a third of children and even some infants coming to the hospital suffer from difficulty in breathing. “Manifestation of allergies is increasing among children due to air pollution,” Ansari says. Jayant Prakash, head of paediatrics department at Indira Gandhi Institute of Medical Sciences, Patna, says, “We have come across cases where newborns do not cry immediately after delivery and have difficulty breathing due to shortage of oxygen in their hyperactive airways because of pollution.”

Mounting evidence

The impact of air pollution on children’s health begins even before they are conceived. It starts by impairing the fertility of both men and women. Research shows that exposure to air pollution affects ovarian reserve in women. The study conducted on women in China showed that the level of anti-müllerian hormone—a predictor of ovarian reserve—changed by -8.8 per cent, -2.1 per cent, -1.9 per cent and -4.5 per cent per 10 µg/m3 increase in PM1, PM2.5, PM10 and nitrogen dioxide (NO₂). “Theoretically, PM with smaller size and larger surface area volume ratio, e.g. PM with diameter ≤1 µm (PM1), is more likely to penetrate through the alveolar capillary barrier and then impact directly the ovarian function via blood circulation,” notes the paper published in Environmental Research on February 1, 2023. Though the underlying mechanism of female fertility decline caused by air pollutants remains unclear, limited evidence speculates that oxidative stress and inflammatory response caused by air pollution may be one crucial pathway, the researchers say.

Similarly, a study in China on 33,876 men showed that exposure to PM2.5 and PM10 decreased total and progressive sperm motility. The findings were published in JAMA Networks on February 17, 2022. If the child is conceived against all odds, air pollution can hinder their development in the uterus as pollutants can cross the placenta into the baby’s blood. In the study published in the Journal of Family and Reproductive Health in June 2017, the researchers from Iran have found an inverse relationship between the exposure to air pollution in the first trimester of pregnancy and the weight of placenta, which sustains the development of the foetus.

A comprehensive review of studies, published in The Lancet Planetary Health reports the presence of black carbon particles in cord blood which enter foetal liver, lungs and brain. The presence of the pollutants continues to harm the growing foetus so much that it tends to increase the risk of preterm birth. This, in turn, can increase the chances of still-birth, low birthweight, underdeveloped lungs in the baby, and death of the baby during or shortly after birth.

Sudhir Gupta, former chairperson of the department of gynaecology at Baba Raghav Das (BRD) Medical College, Gorakhpur, explains how air pollution affects the development of foetus, “Due to pollution, pregnant women cannot get enough oxygen from the ambient air, which affects the natural development of the foetus. Furthermore, the higher the sulphur contents in the air, the greater the risk of miscarriage,” he says.

Bhupendra Sharma, chairperson of the paediatrics department of BRD Medical College, says, “Air pollution can also lead to anaemia in expectant mothers, which greatly reduces the chance of delivering a healthy baby.”

If the child survives the onslaught of pollutants in the utero, multiple studies show that the exposure before and after birth can impair their neurodevelopment skills, such as intellectual functioning, memory and learning, attention and executive functions, verbal language, numerical ability and motor and/or sensor motor functions. “The pollutants that seem to represent the greatest risk are PM2.5, NO₂ and PAHs [polycyclic aromatic hydrocarbons],” states a review of 30 research papers, published in Neuroscience & Behavioral Reviews in May 2022.

Just like in adults, the child’s blood pressure is known to shoot up due to exposure to air pollution during pregnancy—higher the mean PM2.5 and black carbon exposure during the third trimester, higher the newborn’s systolic blood pressure.

Exposure to air pollution in utero can also lead to congenital heart defects in children, making survival difficult. Lungs, too, are not spared from the onslaught. It has been observed that higher the exposure to air pollution during infancy, lower the lung capacity. Acute respiratory infections too seem to affect children who are more exposed to PM2.5. A survey of under-five children indicates that a 10 µg/m3 increase in PM2.5 was associated with greater chances of contracting an infection.

Gut health too gets affected—pollutants inhaled during the first six months of life adversely affect the composition of gut microbes which could increase risk of allergies, obesity and diabetes, and even affect brain development. A 2020 study published in Gut Microbes states that these microbes and their by-products shape appetite, insulin sensitivity, immunity, mood and cognition, and a poor mix of microbes can leave the child prone to asthma, type 2 diabetes and other chronic illnesses.

Exposure to air pollution in the womb can also change the protein activity of the baby. For example, pollutants have been found to affect cell processes such as autophagy, “self-eating” of damaged cells that usually occurs in response to stress, according to a study presented at the European Respiratory Society International Congress in Milan, Italy, on September 12, 2023. Exposure to higher NO₂ was linked to decreased levels of SIRT1, a protein that plays a protective role in stress resistance, inflammation and ageing.

Evidence is also mounting around the impact of pollution sources on health. Studies in Europe have investigated the impact of vehicular emissions on child health and impact on neuron development along the highways. In 2013, a study found correlation between early exposure to traffic pollution and several childhood cancers.

And as if to complete the circle of destruction, exposure to air pollution also impacts the reproductive health of adolescent girls. Higher exposure to particulate matter in utero and throughout childhood has been implicated in the early onset of menarche because these particles seem to have endocrine-disrupting properties.

India’s own evidence

Health experts in India are already generating evidence to implicate air pollution in the high mortality and poor health of children in the country.

In November, the Collaboration for Air Pollution and Health Effect Research, India (CAPHER India), a national research network focused on air pollution and health effects steered by AIIMS New Delhi and the Indian Institute of Technology (IIT) Delhi, has released a policy brief, which says air pollution is the third leading risk factor for deaths in under-five children in the country. For children under 14 years, it is the second leading risk factor for deaths. Since 2010, Delhi, Punjab and Haryana have seen the highest percentage of deaths in under-five children related to outdoor PM2.5 exposures, estimates the policy brief which has reviewed key Indian studies on the issue.

One of the studies published in April 2022 in Science of the Total Environment provides evidence that PM2.5 impacts infant mortality primarily through neonatal mortality. Another study points towards a link between air pollution and stunting. The study by Germany’s Heidelberg University and France’s University of Rennes, published in the Journal of Environmental Economics and Management in May 2022, estimates that the percentages of stunted and severely stunted children in India would drop by 10.4 and 5.17 percentage points, respectively, if average pollution levels were reduced to World Health Organization-recommended levels.

A large-scale study by the Population Council, New Delhi and the International Development Department, University of Birmingham, UK, published in the journal BMJ Global Health in July 2020, confirms that the exposure to PM10 not only affects children but also pregnant women resulting in premature birth. This indicated that the probability of newborn mortality increased by 6 per cent for every 10-unit increase in PM10 levels.

A recent study found a significant correlation between the chemical components of PM2.5 and low birthweight, anaemia and acute respiratory infections in under-five children. The study “Cumulative effect of PM2.5 components is larger than the effect of PM2.5 mass on child health in India”, published in Nature on October 31, 2023, showed that for every 10 µg/m3 increase in PM2.5 exposure, the prevalence of anaemia, acute respiratory infection and low birthweight increased by 10 per cent, 11 per cent and 5 per cent among children under five in India. PM2.5 is a mixture of various components with different sources and toxicities.

The study showed the cumulative effect of PM2.5 components—ammonia (NO3-), fine ammonium (NH4+), elemental carbon (EC) and organic carbon (OC)—to be larger than the effect of PM2.5 mass on child health in India. Another Delhi-based study, published in April 2022, has also established a link between acute exposure to PM2.5 chemical species and mortality during winters. “There might be differences in the methods of studies and study design, including time series, cross-sectional, exposure based health outcomes and many more. However, an interesting fact is that in both these studies NO3 showed the highest impact,” says Ekta Chowdhary, researcher and author of the Nature study.

Yet another area of investigation is childhood cancer. While there is enough evidence to show that exposure to air pollution can lead to cancer in adults, this correlation is not studied adequately in children. There is enough evidence to show that exposure to air pollution can lead to cancer in children. Studies have identified air pollutants such as benzene, NOx and particulate matter as culprits in childhood Non-Hodgkins Lymphoma, a type of cancer that begins in the lymphatic system which is part of the body’s immune system. A study published in January 2023 in Nature found an association between exposure to PM2.5 level and risk of acute lymphoblastic leukaemia among children, which is a cancer of blood and bone marrow. But this correlation is not studied adequately in India.

The latest available data by the National Cancer Registry Programme is only from 2012 to 2016. But it shows a pattern. The proportion of childhood cancers relative to cancers in all age groups in different cities varied between 0.7 per cent and 3.7 per cent. Delhi was the worst affected among places with a cancer registry—the country had 28 Population Based Cancer Registries between these years. Here, as many as 203.1 boys per million are affected by all the broad kinds of cancers compared to just 12.2 per million in Pasighat in Arunachal Pradesh. Patiala’s cancer registry reported 121.2 cases per million boys. Mumbai, which too is facing a pollution challenge, stood at 10th place. In case of girls in the age group of 0-14, the number is 125.4 per million in Delhi compared to 12.1 in East Khasi Hills District. Patiala stood at 9th position with 74 cases per million.

The data from India’s National Cancer Registry Programme shows that Delhi is badly affected by leukaemia too—as many as 84.2 boys per million, between the ages of 0-14 are affected compared to just 7.3 per million in Meghalaya. For girls, this number stands at 47.2 cases per million, the second-highest after Imphal West sistrict in Manipur, compared to just 4.9 per million in Cachar district of Assam. In case of lymphomas, the number stands at 30.7 per million for boys in Delhi, much lower than the 2.3 per million cases seen in Meghalaya. For girls, Delhi has the third highest cases of lymphomas which stand at 10 per million. The report also shows that among the Asian countries studied for boys, Delhi has the highest cases per million followed by China’s Jianmeng. In case of girls, Delhi has the sixth highest number of cases. For all countries included in the study, Delhi has the 6th highest number of cancer cases for boys and 10th highest in case of girls.

Insidious link

There is an insidious link between outdoor and household air pollution. The 2015 report of the Steering Committee on Air Pollution and Health under Union Ministry of Health and Family Welfare estimates that household air pollution can contribute up to 25-30 per cent of outdoor air pollution in India.

Several epidemiological studies are available in India on the effect of household air pollution. The first ever “mother–child” cohort study was carried out by Kalpana Balakrishnan and her team of Sri Ram Medical College, Chennai. They followed the cohort over time to investigate the link between exposure to PM2.5 during pregnancy and low birthweight in an integrated rural-urban setting. This shows that a 10 µg/cum increase in exposure to PM2.5 during pregnancy can decrease birthweight by 4 g, lead to a 2 per cent increase in the prevalence of low birthweight and cause 70 g decrease in birthweight in households using solid fuels.

However, according to a global study “Global, regional, and national burden of ambient and household PM2.5-related neonatal disorders, 1990–2019”, published in March 2023, the global neonatal disorders burden attributable to household PM2.5 has decreased by 38.35 per cent in the past 30 years. This is mainly due to decrease in the household PM2.5-related neonatal disorders burden which decreased by 52.33 per cent during the period, according to the study published in Ecotoxicology and Environmental Safety in March 2023.

According to “State of Global Air/2019” report of the Institute for Health Metrics and Evaluation (IHME), a research institute in the US, India has reduced its proportion of households cooking with solid fuels from 76 per cent in 2005 to 60 per cent in 2017 due to improved access to liquefied petroleum gas. Yet solid fuel use remains high among the lower income groups. This still accounts for about two-thirds of the PM2.5-related neonatal disease burden. In fact, India along with Pakistan, Nigeria and Ethiopia account for about 50 per cent of the total number of neonatal disorders attributable to household PM2.5.

Globally, combined exposure to outdoor and household particulate matter pollution is estimated to have contributed to nearly 500,000 infant deaths in their first month of life. Around 116,000 or 23 per cent of these newborns were in India, according to the recent estimates in IHME’s “State of Global Air/2020” report. This means one of every fourth newborn deaths due to air pollution was in India. In fact, the country-level analysis of the death burden due to air pollution shows that a newborn dies in the country from health concerns associated with air pollution once every five minutes.

Plethora of local and global evidence, thus, builds the case for urgent action to control air pollution. Despite the mounting evidence, people often do not understand how air pollution triggers health conditions that lead to death and illness. This was evident when a nine-year-old girl Ella Kissi Debrah died due to acute asthma attack in south London in 2013 and her mother moved the court challenging that air pollution was responsible for her child’s death. The incident ultimately led to the landmark judgement and coroner’s report in 2020 that made Ella the first person in the world to have air pollution cited as a cause of death.

Kalpana Balakrishnan points out, “Gaps in evidence never close in science. There is already enough evidence on exposures to rest the case. Also remember, absence of evidence is not the evidence of absence. There is already enough for us to act urgently.”

This was first published in the 1-15 December, 2023 print edition of Down To Earth