Large share of India’s PM2.5 not emitted directly, but chemically formed in the atmosphere: CREA Study

India's struggle with air pollution, particularly PM2.5, is a well-documented and pressing environmental and public health crisis. The National Clean Air Programme (NCAP), launched in 2019, aims to reduce particulate matter concentrations by 20-30% by 2024 (later revised to 40% by 2026). However, despite various measures, many Indian cities consistently rank among the world's most polluted. This persistent challenge forms the background for new research, such as the study by the Centre for Research on Energy and Clean Air (CREA), which sheds light on a critical aspect often overlooked: the origin of PM2.5.

The CREA study highlights a crucial distinction in particulate matter pollution. It asserts that a 'large share' of India's PM2.5 is not directly emitted from sources like vehicles, industries, or stubble burning (which would be 'primary' particulate matter). Instead, this significant portion is 'secondary particulate matter,' meaning it is chemically formed in the atmosphere through complex reactions involving precursor gases. These precursor gases primarily include sulfur dioxide (SO2) from coal-fired power plants and industries, nitrogen oxides (NOx) from vehicles and industries, volatile organic compounds (VOCs), and ammonia (NH3) largely from agricultural activities. The study's core finding is that without explicitly addressing these precursor gases, air quality improvements are likely to be 'limited and short-lived,' implying that current strategies might be missing a crucial piece of the puzzle.

Key stakeholders in this complex issue include the Ministry of Environment, Forest and Climate Change (MoEFCC) and the Central Pollution Control Board (CPCB), responsible for policy formulation, monitoring, and enforcement. State Pollution Control Boards play a vital role in local implementation. The industrial sector, particularly coal-fired power plants, contributes significantly to SO2 and NOx emissions, making them crucial stakeholders in adopting cleaner technologies. The agricultural sector, through practices like stubble burning and extensive fertilizer use (leading to ammonia emissions), also emerges as a major contributor to precursor gases. The transport sector, with its emissions of NOx and VOCs, is another key player. Finally, research organizations like CREA, along with the broader scientific community, are critical for providing data-driven insights and informing policy decisions.

This finding carries immense significance for India. Firstly, it necessitates a re-evaluation of the National Clean Air Programme (NCAP) and other air quality management strategies. If a substantial portion of PM2.5 is secondary, then merely controlling direct emissions will not achieve the desired results. Policies must shift or expand to include stringent controls on precursor gases. Secondly, it highlights the inter-sectoral nature of air pollution. Emissions from power generation, industry, agriculture, and transport are all interconnected, demanding integrated policy solutions rather than siloed approaches. Economically, chronic air pollution exacts a heavy toll through healthcare costs, reduced productivity, and impacts on tourism. A more effective strategy, informed by the CREA study, could lead to better public health outcomes and economic benefits.

Historically, India's air pollution control efforts have evolved from focusing on visible smoke to specific particulate matter (PM10, then PM2.5) and gaseous pollutants. The Air (Prevention and Control of Pollution) Act, 1981, provides the legal framework for pollution control, while the Environment (Protection) Act, 1986, serves as an umbrella legislation. Constitutional provisions underpin these efforts: Article 21 (Right to Life) has been interpreted by the judiciary to include the right to a clean environment, while Article 48A (Directive Principles of State Policy) mandates the state to protect and improve the environment. Article 51A(g) places a fundamental duty on citizens to protect and improve the natural environment. This study implicitly calls for stronger implementation of these principles by targeting the root causes of secondary PM2.5.

The future implications are profound. Policy frameworks like NCAP will need to incorporate specific targets and technologies for reducing SO2, NOx, VOCs, and ammonia. This might involve mandating Flue Gas Desulfurization (FGD) units in power plants more rigorously, promoting cleaner fuels, encouraging sustainable agricultural practices to reduce ammonia emissions, and investing in advanced emission control technologies across industries. Enhanced inter-ministerial coordination (e.g., between MoEFCC, Ministry of Agriculture, Ministry of Power, Ministry of Road Transport and Highways) will be crucial. Furthermore, the study underscores the need for continuous scientific research and robust monitoring to understand the complex atmospheric chemistry and identify regional pollution hotspots. Addressing secondary PM2.5 effectively will be vital for India to achieve its air quality goals, safeguard public health, and ensure sustainable development, aligning with global commitments like the Sustainable Development Goals (particularly SDG 3 on good health and well-being, and SDG 11 on sustainable cities and communities).