What is airshed management? And can it be used to curb air pollution in India?
The Indian government is moving to a new way of dealing with air pollution which recognises that the problem does not respect political borders. 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. Three years later, the National Clean Air Programme is widely described as ineffective, and India continues to rank among the top five most polluted countries in the world. Now, scientists are looking at a different approach to tackling the country’s toxic air, one based on the recognition that pollution transcends national and state borders. The National Clean Air Programme 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. Air pollution is not restricted to geopolitical boundaries,” points out SN Tripathi, professor of civil engineering at the Indian Institute of Technology Kanpur and a member of the National Clean Air Programme 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 do not 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 it works 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 do not have any control over the pollution in their jurisdiction. That is why we need an airshed approach to 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 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. “The World Bank is supporting a team of Indian experts who have applied several internationally adopted models, including Greenhouse Gas - Air Pollution Interactions and Synergies 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 on the Indo-Gangetic Plain, particularly the development of air action plans in Uttar Pradesh and Bihar using an airshed management approach.” 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 and the process is still being deliberated. Uttar Pradesh However, some states feel urgent action is required. 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 Greenhouse Gas - Air Pollution Interactions and Synergies model. The state plans to distribute 1,00,000 free stoves and electric tandoors to restaurants and eateries.