CHENNAI: There has been a considerable dip in the concentration levels of particulate matter (PM2.5) in Tamil Nadu, both in rural and urban areas, where the National Clean Air Programme (NCAP) is being implemented, says a study conducted by Delhi-based think tank Climate Trends.
The study titled ‘Status of urban and rural air quality exposure at national scare: A comparative analysis’ was conducted to assess the overall air quality improvement in all the states and major metropolitan cities using satellite data available with IIT Delhi and the Central Pollution Pollution Board (CPCB)-owned ground monitors from 2017 to 2022.
The results of the study show a 22% drop in PM2.5 levels in Tamil Nadu compared to 2017. In 2022 the PM2.5 level was 32.9 ug/m3 (micrograms per cubic metre), while in Chennai, it is currently around 29 ug/m3. In 2017, the state’s annual average was 43 ug/m3.
According to CPCB’s national ambient air quality standards (NAAQS), the annual average safe limit for PM 2.5 is 40 ug/m3 and for PM10 it is 60 ug/m3. However, WHO’s revised guidelines for PM 2.5 and PM 10 are 5 ug/m3 and 15 ug/m3, respectively.
One of the key highlights of the study is that the air pollution levels were uniform in both rural and urban settings, which shows that particulate matter doesn’t have boundaries. “Efforts to mitigate air pollution should encompass a more comprehensive approach that addresses pollution sources in both rural and urban settings. Managing the air quality of entire airsheds should be the preferred policy route,” the study says.
Since most of the ground monitors are located in urban areas, the researchers have used scientific methods to calculate surface PM2.5 from aerosol optical depth (AOD) derived from satellite data to measure pollution in rural areas. A national PM2.5 database has been developed by standardising an algorithm for India (SAANS).
M Jayanthi. chairman, Tamil Nadu Pollution Control Board (TNPCB), told TNIE there are three non-attainment cities in Tamil Nadu - Chennai, Tiruchy and Madurai - where NCAP activities are underway. “Source apportionment studies and carrying capacity assessment were being done in all three cities, and various other activities like improving green cover, solid waste management, providing e-charging stations, end-to-end road paving etc are being done to improve the ambient air quality. TNPCB is also increasing the number of Continuous Ambient Air Quality Monitoring Stations in the state.”
Aarti Khosla, director, Climate Trends, said: “The analysis reflects the progress being made under the NCAP. The analysis also highlights that rural air pollution levels aren’t far behind.”
SN Tripathi, Steering Committee Member, NCAP, said the projected decrease, according to the new NCAP guidelines, is up to 40% for 2019 to 2026, so each state should aim to reduce 7% of their average PM2.5 levels annually.
“According to this calculation, by the end of 2022, each state should have at least 20-25% annual average PM2.5 reduction levels on the conservative side and a 30-35% reduction on the positive higher side.”