The Centre for Study of Science, Technology, and Policy (CSTEP), a Bengaluru-based think-tank, has estimated that Particulate Matter (PM) 2.5 emissions in Chennai could shoot up by over 27% by 2030. The data was revealed on August 25, at the India Clean Air Summit (ICAS) 2023, which was organised by CSTEP. In a press release, CSTEP noted that “if certain prioritised measures are not adopted, PM2.5 emission in Chennai is estimated to shoot up by over one-fourth by 2030. However, if certain measures are adopted, the same will be reduced by 27%.”

PM or particulate matter, also called particle pollution, is a mixture of solid particles and liquid droplets found in the air. PM10 is the term used for inhalable particles with diameters of 10 micrometres and smaller, and PM2.5 is used for inhalable particles with diameters of 2.5 micrometres and smaller.

While the findings may appear grim, the data on emissions inventory also suggests that a significant reduction is possible in the non-attainment cities of Chennai, Madurai, Trichy, and Thoothukudi in Tamil Nadu, if preventive measures are adopted. Non-attainment cities are those that do not meet the national ambient air quality standards (NAAQS) under the National Air Quality Monitoring Programme (NAMP). An emissions inventory is a database that lists the amount of air pollutants discharged into the atmosphere during a year or other time period. 

CSTEP prepared an emissions inventory for 76 cities across 17 states and Union Territories of India. In Tamil Nadu, the emissions inventory was developed for  Chennai, Madurai, Trichy, and Thoothukudi. According to the CSTEP, in 2019-20, Thoothukudi was found to have had the highest PM emissions, owing to the presence of heavy industries, including thermal power plants. 

 The study also noted that in the case of a Business As Usual (BAU) scenario, by 2030, the emission in Chennai is projected to see the highest increase projected to be 27%, followed by 25% in Trichy, 20% in Madurai, and 16% in Thoothukudi. However, if these four cities adopt all the recommended prioritised measures, the report estimated that by 2030 the emission will be reduced by as much as 36% in Trichy, 34% in Madurai, 27% in Chennai, and 20% in Tuticorin.

Talking about preventive measures, Pratima Singh, Senior Research Scientist, Air Quality, CSTEP, suggested that it should involve a shift in fuel consumption from fossil energy to cleaner renewable energy. “Some of the prioritised measures include the shift in fuel usage from coal to the cleaner ones, better road infrastructure including materials utilised wherein road degradation gets reduced, stricter emission control norms for industries and transportation systems,”  Pratima noted. 

R Ethirajan, Environmental Engineer at the Tamil Nadu Pollution Control Board (TNPCB), stated that defining the ideal air quality benchmark for a city, state, or region, presented a complex challenge. The question of what constitutes ‘good’ air quality is intricate and depends on the context. “City action plans are earnestly striving to address this intricate issue. In cities like Chennai, Madurai, Trichy, and Thoothukudi, we are rigorously assessing the air quality landscape. Specifically, we are examining the PM10 levels within our Non-Attainment Area Program (NAAP) cities in Tamil Nadu. Our goal is to establish a comprehensive understanding of these dynamics and craft effective strategies for cleaner air,” he emphasised. 

While the CSTEP study itself is about PM2.5 which is smaller in size, the TNPCB also assesses the presence of PM10 in the air.