“The situation is very, very grave,” Dr. Vandana Prasad says of Delhi’s air pollution. A community paediatrician and public health professional, she is the national convenor of the Public Health Resource Network (PHRN). She has lived in Delhi for 61 years practising as a public health expert and as a primary care physician for 30 years.
“The changes are stark,” she adds. “It's not an incremental increase; it's an exponential increase in the last few years. Its impact is so severe that this is a public health emergency for all people, but especially for children because they're so much more vulnerable,” Dr. Prasad tells Hot Rock.
In her work with children from low-income backgrounds, she sees them coughing all the time, noses running. For children under 12, masks are not recommended because their bodies cannot handle the filtration. Air pollution therefore affects them orders of magnitude higher than adults.
She says the effect on their lungs is especially crucial as they are growing. “Especially, I think that the implication for babies is very, very much higher. Their lungs are growing. Lungs grow all the way through childhood, but the rate of growth is very high during the first two to three years of life. And the surface area of the lungs is much higher. Children breathe much faster. So, all the impact of this dirty air falls on them. Air pollution prevents their lungs from growing to full potential. That effect is for life.
“It's tantamount to children smoking cigarettes.”
Because lungs furnish oxygen for the entire work of the body, which includes play, study, cognitive functions, brain function, and in fact, everything, the effects of polluted air span the gamut of problems. Research shows asthma and bronchitis are common among children who breathe polluted air. Long-term effects include cancers.
It’s an entire who’s who of pollutants—PM2.5 (particles less than 2.5 microns across), PM10 (less than 10 microns across), sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide—that passes for air in Delhi and many other places.
After Diwali, air quality was so poor that some parts of the city overshot 500 AQI, the equivalent of several packs of cigarettes a day.
Now, the crisis is way past emergency. It’s killing people. High pollution means high emission and low dispersion, says Dr. Swagata Payra, associate professor at Birla Institute of Technology, Mesra. In the summer, people in Delhi use a huge number of ACs, which contributes to pollution but meteorological conditions help to disperse the pollutants.
Temperatures plummet when winter starts. Prevailing winds get very low. The sinking cold air presses down the smoke from vehicles, coal plants, crop fires from other states and whatever people are burning and burning with. A smoggy miasma envelops Delhi and north India. (Smoke plus fog is smog). The very act of breathing becomes dangerous and lethal.
Payra explains that a few factors go into making fog: low temperature; low winds, stable atmosphere, high relative humidity; availability of aerosols which act as cloud condensation nuclei (CCN).
Delhi, being one of the most polluted cities, has lots of air pollutants from different sources. Moisture pools around and is absorbed by these particles, and cools, forming stratus clouds at a lower level.
High relative humidity saturates due to low temperature over CCN. That is, Payra explains, any gas or liquid gets liquified or solidified when temperature gets low. The presence of water vapour, which denotes high relative humidity (RH), helps to form fog in low temperatures. With low wind conditions in winter, the atmosphere is stable, which allows the fog to grow after night-time cooling.
Chennai, in contrast, has high relative humidity and a lot of pollution also. But high temperatures and high wind speeds disperses any fog that may form.
“Inversion of temperature profile happens in stable atmosphere. That helps the fog formation,” Payra tells Hot Rock.
As to why north India, especially the Indo-Gangetic plain (IGP) chokes on this smog, it is an agricultural and industrial belt. Western disturbances bring water vapour and low temperatures. This fog (and smog) is highly acidic and contributes to health problems such as asthma and bronchitis.
China was in the same situation as India. Beijing’s air was a witches’ brew during most of the first decade of this millennium. It subsequently instituted rigorous standards for coal plants and other industries, and emission standards for vehicles.
India launched its own National Clean Air Programme (NCAP) in January 2019 with an aim to improve air quality in 131 cities (non-attainment cities and Million Plus Cities) in 24 States/UTs. It aims to reduce Particulate Matter10 (PM 10) concentrations by 40 per cent by 2025-26.
According to this report, 82 cities under NCAP have been provided annual targets of 3-15 per cent reduction in PM10 levels to achieve an overall improvement in air quality up to 40 per cent PM10 levels. 49 cities under the XVth Finance Commission air quality grant have been given an annual target of 15 per cent reduction in average Particulate Matter10 (PM10) concentrations and improvement of good air quality days (Air Quality Index less than 200).
The report notes that PM10 levels of Mumbai in the year 2021-22 was 102 µg/m3 an improvement of 34 per cent with respect to base year 2017-18. But the progress the report shows is not enough. Many areas, urban as well as rural, suffer from acute air pollution. There is no rigorous implementation of air quality standards.
The health effects make for morbid reading. According to the State of Air report 2025, India had more than two million premature deaths due to polluted air. Dr. Vandana Prasad says the fundamental issue is of urban planning and lack of equity. Indian cities are not built to sustain these concentrations of population.
Dr. Prasad says we have to establish green public transportation system, including buses. “We have to definitely curtail private cars. There's no way out of it.”
It’s not just transport that is needed to save the day but a combination of “decent alternatives” such as working from home, stopping farm burning, among others.
Whether it is climate change and pollution, food prices, or water and sanitation, living conditions, “the situation is just dire and something needs to be done about it. Other countries have done it. It's not as though nobody's ever done it.”
