India has seen a decline in particulate matter (PM) pollution since 2016, but this drop is likely not due to a key government policy designed to tackle air pollution, according to a new study published in the journal Science Advances.
The National Clean Air Programme (NCAP) was launched by the Union Ministry of Environment, Forest and Climate Change in 2019. Under this programme, 131 cities with consistently high levels of particulate matter exceeding the National Ambient Air Quality Standard (NAAQS) issued by India were given a target of reducing particulate concentration by 20-30 per cent by 2024 relative to 2017.
India has missed the target and has revised it to achieve up to 40 per cent reduction by 2025-26 relative to 2019-2020.
PM is the sum of all microscopic solids or liquid droplets and is an air pollutant. It is divided into four groups: PM10 (coarse particulate matter less than or equal to 10 micrometres or μm in size), PM2.5 (fine particulate matter measuring 2.5 μm or lower in size), PM0.3 (particles with a diameter of less than 0.3 μm and called quasi-ultrafine particles) and PM0.1 (ultrafine particulate matter less than or equal to 0.1 μm).
“We find a declining trend in average PM2.5 concentrations since 2016-2018, particularly in northern India, and confirm that these reductions are not attributable to meteorological variability nor to NCAP,” the researchers wrote in their study.
“Air quality can be influenced by action taken and meteorological conditions,” Anumita Roychowdhury, executive director of research and advocacy at the Centre for Science and Environment (CSE), a New Delhi-based think tank, told Down To Earth (DTE). She was not associated with the study.
As of November 2024, the country has 966 operating stations in 419 cities or towns across 28 states and seven Union territories, which is lower than the United States, European Union and China.
“In India, there is a lack of air pollution exposure data, which is crucial for researchers to conduct population-based and nationwide studies on the various impacts of ambient air pollution,” Ayako Kawano, Doerr School of Sustainability from Stanford University, told DTE.
To overcome this, researchers used a machine learning model to analyse daily PM2.5 dataset for India over 2005-2023, with data from remote sensing. This data, Kawano said, could help researchers and policymakers investigate and address the impacts of ambient air pollution in India.
The analysis found that much of India saw substantial increases in PM2.5 concentrations between 2011 and 2016, compared to 2005-2010, barring Jammu and Kashmir, Punjab and Rajasthan. During 2017-2022, this increase was moderated. The most notable decreases in PM2.5 levels were seen in Jammu and Kashmir, Punjab, Haryana, Delhi and Rajasthan.
These findings were consistent with previous studies that found PM2.5 levels dropped by 43 per cent in 2020 compared to 2017-2019 in urban areas. Other various air quality control policies in India, including the implementation of Bharat Stage BS-VI emission standards and the closure of power plants near Delhi, may have contributed to this decline.
Of the cities analysed, the average New Delhi resident has consistently faced the highest population-weighted average of PM2.5 concentrations, with 88.67 μg / cubic metres in 2022, more than double of India’s annual national air quality guideline of 40 μg / cubic metre. Residents of Kolkata and Mumbai have also experienced PM2.5 levels exceeding national limits.
Still, residents in all mega-cities have experienced a moderate decline in PM2.5 exposure since 2016-2018, with Mumbai seeing the most substantial decline of 10 per cent, followed by 8 per cent in New Delhi between 2020 and 2022, the study highlighted.
The declining trend in PM2.5 concentrations from 2016 to 2022 was likely partly influenced by meteorological variability like precipitation and relative humidity in the southern regions, but not in the northern regions. Prior to 2015, increased anthropogenic activities and not meteorological conditions drove high concentrations of the pollutant.
The team also assessed how implementing NCAP has impacted ambient PM2.5 concentrations to date. They compared changes in subdistricts in targeted and non-targeted areas (where NCAP was not implemented), before and after initiation of NCAP. They found no evidence to support that NCAP contributed to reducing PM2.5 concentrations in 2021 and 2022.
Instead, the decline could be due to COVID-19 pandemic lockdown and other air quality control policies in India, including the implementation of BS-VI emission standards that mandate vehicles to adhere to emission limits and the closure of power plants near Delhi.
Kawano is now using this data to analyse the health impacts of exposure to PM2.5. Though the declining trend is consistent with a 2020 study, they defer on the attribution. The 2020 paper had attributed the decrease to recent policies and regulations, including NCAP.
In a 2024 report, CSE highlighted flaws and areas of improvement for NCAP. For instance, the government was tracking progress by only measuring PM10. “This is a low-hanging fruit. The government should adopt PM2.5 and not PM 10 as basis for measuring progress,” Roy Chowdhury explained.
In most cases, contribution of combustion sources to PM2.5 concentration— including industry, vehicles and waste burning — is substantial, according to the CSE report. Measuring PM2.5 is also important from a public health perspective, it underlined.
The CSE report also found that 64 per cent of the total funding from the 15th Finance grant went into mitigating road dust. Much lesser funds were provided for combustion sources that emit more harmful pollutants.
Additionally, MoEFCC allocates funds to 82 cities under the NCAP programme. A convergence funding like Swachh Bharat mission for waste management and Faster Adoption & Manufacturing of Electric Vehicles in India (FAME-II), and other sectors, partly addresses combustion sources.
“The NCAP component should be supported to push cities to deliver. Convergence funding should also be strengthened,” Roychowdhury added.
She also calls for reform of NCAP in what is being tracked and how progress is being tracked, design and implementation. “Action should be strengthened to address all combustion sources from industries, construction, wastes and the like,” she added.