Manali in North Chennai Emerges as India’s Worst Ground-Level Ozone Pollution Hotspot
Manali, the industrial hub in North Chennai, has emerged as India`s most severe hotspot for ground-level ozone pollution, recording the highest ozone concentration in the country this year, according to data from the Central Pollution Control Board (CPCB).
A monitoring station in Manali recorded an alarming ozone level of 500 micrograms per cubic metre on May 19, while another station in the area reported 361 micrograms per cubic metre on May 3. These figures are significantly higher than the national air quality standard of 100 micrograms per cubic metre based on an eight-hour average.
Experts from the Centre for Research on Energy and Clean Air (CREA) noted that ozone levels in Manali exceeded permissible limits on 24 days during May, highlighting the growing air pollution concerns in the region.
Manali is home to several major industries, including petrochemical plants, oil refineries, fertiliser factories and thermal power stations. However, the Tamil Nadu Pollution Control Board (TNPCB) stated that industrial emissions alone are not responsible for the rise in ozone levels. Vehicular emissions and volatile organic compounds (VOCs) are also key contributors to ozone formation.
Despite the ozone concerns, TNPCB officials pointed out that Manali`s Air Quality Index (AQI) has improved from 118 in 2018 to 64 in 2026. They also noted that most of the highly polluting industries in the region have shifted to cleaner fuels such as CNG, LPG and naphtha.
Ground-level ozone is a harmful air pollutant formed when nitrogen oxides and volatile organic compounds react under sunlight. Unlike the protective ozone layer in the upper atmosphere, ground-level ozone can cause respiratory problems, aggravate lung diseases and negatively impact the environment.
