PM2.5 is a concept that refers to fine particulate matter, which are tiny solid or liquid particles suspended in the atmosphere. These particles measure 2.5 micrometres or less in diameter, making them about 40 times smaller than the width of a human hair. This microscopic size allows PM2.5 to penetrate deep into the respiratory system and even enter the bloodstream, posing a significant health threat.
The concept's prominence in India is a response to the country's severe air pollution, which is among the highest globally. The regulatory framework for addressing this problem is overseen by the Central Pollution Control Board (CPCB), a statutory body that exercises powers under the Air (Prevention and Control of Pollution) Act, 1981. The CPCB sets the National Ambient Air Quality Standards (NAAQS), which were last notified on November 18, 2009.
The mechanism for tracking this pollutant involves a network of monitoring stations, including Continuous Ambient Air Quality Monitoring Systems (CAAQMS), which provide real-time data. The concentration of PM2.5 is one of the eight pollutants used to calculate the Air Quality Index (AQI), a tool to communicate air quality to the public.
A major recent development is the launch of the National Clean Air Programme (NCAP) in 2019 by the Ministry of Environment, Forest, and Climate Change. The NCAP is a multi-sectoral initiative targeting a 20-30% reduction in particulate matter concentrations by 2024, relative to 2017 levels. Furthermore, the Commission for Air Quality Management in National Capital Region and Adjoining Areas Act, 2021, established the CAQM as a statutory body for coordinated air pollution management in the NCR airshed.