In 2019, air pollution in India caused the premature deaths of more than a million people. That same year, the government established the National Clean Air Programme (NCAP). Three years later, the NCAP is widely described as ineffective, and India continues to rank among the top five most polluted countries in the world. Now, scientists are looking to a different approach to tackling the country’s toxic air, one based on the recognition that pollution transcends national and state borders.
The NCAP was formulated to tackle air pollution in cities, specifically to reduce particulate matter (PM2.5) pollution by 20%-30% from 2017 levels by 2024. But the nature of air pollution means there are limitations to a policy that focuses on urban areas.
PM2.5 refers to tiny inhalable particles – particulate matter – with a diameter of 2.5 micrometres.
These particles are a mixture of solid and aerosol chemicals, mostly produced by burning fuels such as petrol, diesel, oil or wood.
PM2.5 pollutants are much smaller than the diameter of a human hair. Because these particles are so small, they can penetrate the lungs deeply, causing harm to people’s health
“Air pollution is not restricted to geopolitical boundaries,” points out SN Tripathi, professor of civil engineering at the Indian Institute of Technology (IIT) Kanpur and a member of the NCAP steering committee. South Asia’s geography and weather patterns mean that pollutants can travel long distances: a 2020 study of 22 regions showed that 46% of air pollution (adjusted for population distribution) originates from another Indian state.
“Because of the transboundary dispersion of air pollution, smaller towns that don’t have as many polluting industries experience high levels of pollution that come from larger cities,” says Kalyani Tembhe, programme officer at the Centre for Science and Environment, a think-tank in New Delhi.
“Air pollution depends on meteorology, topography and land-use patterns,” Tripathi agrees.
Because of this, Indian states are looking at new ways to tackle the crisis, with many planning to adopt airshed management. The World Bank defines an airshed as a common geographic area where pollutants get trapped, creating similar air quality for everyone. “We can reorganise… natural processes that govern the air, and identify airsheds,” Tripathi says.
The concept is demonstrated by a 2019 study that found approximately half of the population-weighted PM2.5 in Delhi comes from outside the territory, of which 50% is from Haryana and Uttar Pradesh. In Punjab, about 60% of PM2.5 does not originate within the state, with about half coming from outside India and half from other Indian states. In Uttar Pradesh, only half of PM2.5 originates within the state.
Sagnik Dey, a professor at the Centre for Atmospheric Sciences at IIT Delhi, has identified the major regional airsheds that impact India, based on satellite data for PM2.5.
“The whole idea is that, within an airshed, the overall patterns of air quality from season to season are similar over the long term. There are nine to 11 airsheds in India. Some, like the Indo-Gangetic Plain airshed, within which lie two or more regional airsheds, are gigantic,” he says. The Indo-Gangetic Plain covers the states of Rajasthan, Punjab, Uttar Pradesh, Delhi, Haryana, Bihar and West Bengal, and extends to Nepal, Bangladesh and Pakistan.
How would airshed management work in India?
The idea of airsheds is not new. The Canadian province of British Columbia and California in the US have both used an airshed approach to tackle air pollution. The Air Quality Act of 1967 divided California into 35 districts with similar geographic, topographic and meteorological conditions, where pollution is regulated by the California Air Resources Board. By 2019, this approach had achieved a 98% reduction in emissions from “heavy-duty engines” compared with 2010 levels.
In South Asia, the areas with critically high PM2.5 concentrations that would benefit from an airshed approach include the western and central Indo-Gangetic Plain; the Brahmaputra basin (India and Bangladesh); middle India (east Gujarat/west Maharashtra and Odisha/Chhattisgarh); the northern and central subcontinent (Pakistani and Indian Punjab and part of Afghanistan); and the southern subcontinent (south Pakistan and west Afghanistan).
PM2.5 concentrations in villages and small towns in the Indo-Gangetic Plain are often similar to or higher than the nearest large city, indicating that air-quality management cannot be restricted to cities. “These towns don’t have any control over the pollution in their jurisdiction. That is why we need an airshed approach as air-quality management. We need a legal policy to ensure that cities take responsibility,” Tembhe says.
“The idea is that all cities that lie within an airshed need to coordinate with each other for an effective solution,” Dey adds. “For example, 80% of the airsheds of Lucknow and Kanpur [in Uttar Pradesh] overlap. Similarly, Dhanbad [in Jharkhand] and Asansol [in West Bengal] have a very big overlap in their airshed. So they will benefit by sharing their resources and data.”
Now, the World Bank is giving technical and advisory support to the process of developing the country’s first large Airshed Action Plan for the Indo-Gangetic Plain, across seven union territories and states. The Indo-Gangetic Plain is one of the most polluted areas in the country, contributing to 46% of premature deaths.
Towns in the Indo-Gangetic Plain don’t have any control over the pollution in their jurisdiction… We need a legal policy to ensure that cities take responsibilityKalyani Tembhe, Centre for Science and Environment
“The World Bank is supporting a team of Indian experts who have applied several internationally adopted models, including GAINS in Europe, North America and China,” says Karin Shepardson, lead environmental specialist at the World Bank. “Now we are helping Indian partners to tailor it to local conditions in the states in the Indo-Gangetic Plain, particularly the development of air action plans in Uttar Pradesh and Bihar using an airshed management approach.”
GAINS stands for Greenhouse gas and Air pollution Interactions and Synergies, and refers to a model used to assess strategies that combat air pollution and climate change at the same time.
How the technical model is ultimately translated into airsheds for management purposes is something the government has to decide, says Shepardson. The government is yet to define airsheds for India; the process is still being deliberated.
Uttar Pradesh takes first step on airshed management
However, some states feel urgent action is required before then. Uttar Pradesh is the first to adopt an airshed action plan. Speaking at the India Clean Air Summit in Bangalore in August, Ashish Tiwari, the secretary of the Department of Environment, Forest and Climate Change of Uttar Pradesh, announced that, with the World Bank’s help, the state has identified clean cooking as the most cost-effective intervention, based on the GAINS model. The state plans to distribute 100,000 free stoves and electric tandoors to restaurants and eateries.
“Introduction of clean fuel will definitely have a huge impact,” Tembhe says, but she adds a word of caution. “While it’s a good solution, it’s not a permanent solution,” as sources of pollution need to be identified at the airshed level.
“It makes more sense to develop an airshed management plan for the entire Indo-Gangetic Plain region, as pollutants don’t stop at state lines,” says Alan Lloyd, a senior research fellow at the Energy Institute of the University of Texas at Austin. He recommends the formation of an air resources board for the Indo-Gangetic Plain, similar to the one in California, that combines richer and lower-income areas within the same geographic area.
In a big airshed like the Indo-Gangetic Plain, we need to understand the emission load of each statePrathima Singh, Center for Study of Science, Technology and Policy
“However, the perfect should not get in the way of the good. It is critical to get good data to put into the model. So, if Uttar Pradesh is ahead in data collection, then a lot can be learned while the other states acquire more and better data,” he adds.
“In a big airshed like the Indo-Gangetic Plain, we need to understand the emission load of each state, so they can coordinate among each other in terms of governance and infrastructure to ensure that these major polluting sources can be reduced,” explains Prathima Singh, an air-pollution scientist at the Center for Study of Science, Technology and Policy (CSTEP), a think-tank in Bangalore.
A 2019 study found that secondary PM2.5 (which is formed though the interaction of particles that were emitted directly) is the major source of pollution in most of the Indo-Gangetic Plain states, followed by domestic cooking. In Delhi, 20% of PM2.5 comes from mobile sources, such as cars, buses, aeroplanes and construction equipment.
There are also seasonal variations, Singh adds. In winter, stubble burning affects the entire Indo-Gangetic Plain. In summer, dust pollution from the alluvial soil in the river belt is a big contributor to air pollution.
A snapshot taken by a NASA satellite in November 2017 of the smog created by stubble burning showed that both India and Pakistan were affected equally. The smog caused a health emergency, with schools, industries and airports shutting down in both countries.
Airshed management needs international cooperation
Despite a number of efforts to revive the Malé Declaration, an agreement to address transboundary pollution signed by Bangladesh, Bhutan, India, Iran, the Maldives, Nepal, Pakistan and Sri Lanka as far back as 1998, “as far as I know, nothing has come of it”, Tembhe says.
This demonstrates why “international cooperation is important in the Indo-Gangetic Plain”, Tripathi says. “Punjab, especially Amritsar and Jalandhar, are heavily influenced by pollution coming from Pakistan. A large part of the pollution from the Indo-Gangetic Plain goes to Bangladesh and, at certain times of the year, pollution comes from Bangladesh to West Bengal and Jharkhand.”
Ultimately, for airshed management in India to work, enforcement has to be taken seriously. This was a key element of its success in California, says Lloyd. “Previous plans in India failed because of a lack of serious enforcement. Fines must be commensurate with the violation, and public health must be addressed asap.”