New Delhi, Feb 9 : A recent study by three scientists on the adverse impact on air quality because of industrial emissions, has cleared many long-standing misgivings. And, that includes the fact that industries are the biggest polluter of the environment. The report literally cleared the air after the authors R.L. Verma of the Asian Institute of Technology, Bangkok, Thailand, J.S. Kamyotra, freelance consultant, New Delhi, and Balram Ambade, National Institute of Technology, Jamshedpur, Jharkhand, did a detailed study on the air quality of Thoothukudi (former Tuticorin). The authors compared the air quality and air quality index (AQI) of Thoothukudi with those of other industrial clusters of Tamil Nadu, and with the four major metros on various parameters. The ambient air quality of Thoothukudi was compared on concentration levels of key air pollutants -- particulate matters (PM10, and PM2.5), sulphur dioxide (SO2), nitrogen oxide (NO2,) and the Air Quality Index (AQI) from January 2015 to December 2020 with those of Delhi, Mumbai, Kolkata, and Chennai. Comparison was also made with those of Manali, Cuddalore, and Coimbatore, major industrial clusters of Tamil Nadu. The study revealed that the concentration levels of PM10, PM2.5, and NO2 in Thoothukudi were not only comparable with those observed in Mumbai, Kolkata, and Chennai, which too are coastal cities, but also those with the industrial clusters between 2015 and 2020. Only Delhi proved to be an outlier with double the concentration level of pollutants. For the authors it proved that local meteorology plays an important role in the ambient concentration levels of air pollutants. Even the AQI of Thoothukudi like other metros (except Delhi) and industrial hubs, reported less than 100, which signifies good quality air. Similarly, the concentration level of air pollutants during the operation of Sterlite Copper during 2017 and 2018, and after its closure in 2018 and 2019 showed no significant change in the concentration levels of SO2 at Thoothukudi. Even during its operation, the SO2 levels were in the range of 13-15 ug/m3, well below the 24- hour ambient air quality standard of 80 ug/m3 and was comparable to other industrial clusters. The authors discovered that other sources of air pollution like vehicle exhausts from burning of diesel, petrol and compressed natural gas, gases from thermal power plants, small scale industries including brick kilns, resuspended dust on the roads due to vehicle forest fires etc have been glossed over or not given their due importance. For instance, the past two decades have seen a seven-fold increase in the number of passenger cars on India's roads leading to significant increases in urban air pollution levels and associated health problems. "In terms of air pollution, road transportation was responsible for more than 40 per cent of total nitrous oxide (NOX) emission of 3.3 million tons and around 7 per cent combustion-related PM2.5 emissions in 2019," argues an International Energy Agency report titled "Air Quality and Climate Policy Integration in India: Frameworks to deliver co-benefits. The strong economic growth witnessed between 2010 and 2019 too had a role in the worsening air quality because the country's total energy consumption increased by one-third in that period. "Given that India's energy sector is fossil fuel intensive, CO2 emissions increased by nearly 50 per cent over the same period, despite noted improvements to CO2-intensity and GDP energy-intensity," says the IEA study. The heavy reliance on traditional biomass for cooking and heating in many of the poorer households in India, which have little to no access to clean cooking, results in high levels of harmful PM2.5 pollution and also contributes to a much lesser degree to NOX and SO2 emissions. NOX emissions stem primarily from oil combustion in the transport sector and thermal power plants, which account for approximately 40 per cent and 25 per cent of India's NOX emissions, respectively. Half of India's SO2 emissions arise from thermal power plants and industrial activities add another third. Even agricultural activities produce two key pollutants namely ammonia (NH3) and nitrous oxide (N20) emissions. /IANS