Gurgaon: Haryana is among the country’s emerging ozone hotspots. Ground-level ozone has emerged as a growing air quality concern in Haryana even as particulate pollution remained relatively subdued during May.Twelve of the state’s 30 monitoring stations recorded breaches of national standards during the month, according to data from Central Pollution Control Board’s (CPCB) continuous ambient air quality monitoring network. Nathu Colony in Ballabgarh recorded the seventh-highest ground-level ozone concentration in India during May.CPCB data shows that 40% of Haryana’s monitoring stations reported at least one day when the maximum rolling eight-hour ozone concentration exceeded the National Ambient Air Quality Standard (NAAQS) of 100 micrograms per cubic metre (µg/m3).Nationally, CPCB data analysed by Centre for Research on Energy and Clean Air (CREA) showed that while winter air quality management remains focused on particulate matter, Haryana may increasingly need to address ozone pollution during the summer months.Unlike particulate pollution, which is often concentrated around emission sources, ozone can travel long distances and affect areas far from where its precursor pollutants are emitted, making it a regional air quality challenge requiring coordinated action across sectors and districts. The findings underscore the rise of a pollutant that is increasingly becoming a summer air quality challenge across the state, even as particulate pollution levels ease after winter.The national analysis by CREA found that Nathu Colony in Ballabgarh registered a maximum eight-hour average ozone concentration of 278 µg/m3, nearly three times the national standard.The highest ozone concentration in the country was recorded at Manali village in Chennai (500 µg/m3), followed by MIET College in Meerut (425 µg/m3), Manali in Chennai (361 µg/m3), Buddha Colony in Muzaffarpur (306 µg/m3), Pusa in Delhi (292 µg/m3) and Hakimapada in Angul, Odisha (292 µg/m3). Ballabgarh ranked seventh nationally, ahead of stations in Moradabad, Tonk and Sri Ganganagar.Health experts warn that exposure to elevated ozone concentrations can irritate airways, reduce lung function, worsen asthma and other respiratory illnesses, and increase hospital visits among vulnerable populations. The pollutant can also damage crops and natural vegetation.Within Haryana, F-Block in Sirsa recorded the highest number of exceedance days, with ozone levels crossing the prescribed limit on 13 days during May. Amity University in Panchgaon followed with 11 exceedance days. Shyam Nagar in Palwal and Urban Estate-II in Hisar recorded six exceedance days each, while the NISE monitoring station at Gwal Pahari in Gurgaon reported four days above the standard.Other stations reporting exceedances included Gobind Pura in Yamuna Nagar and Huda Sector in Fatehabad, which recorded two exceedance days each. Police Lines in Jind and IMT Manesar also recorded two exceedance days, while stations in Karnal, Kurukshetra and Ballabgarh recorded one exceedance day each.While Ballabgarh recorded the state’s highest ozone concentration at 278 µg/m3, Police Lines in Jind registered a peak value of 198 µg/m3, nearly double the national standard. IMT Manesar recorded 177 µg/m3, while Palwal and Hisar reported peak concentrations of 169 µg/m3 and 168 µg/m3, respectively.Analyst at CREA Manoj Kumar told TOI, “The distribution of ozone hotspots across Haryana reflects the secondary nature of ozone pollution. Ozone is formed through sunlight-driven reactions between NOx and VOCs, and its concentrations are strongly influenced by atmospheric transport and photochemical processes, often leading to peak levels away from the original emission sources.”Kumar said the pattern observed in Haryana indicates that ozone pollution is not confined to major urban centres and can affect peri-urban and semi-urban regions as pollutants are transported across districts under favourable meteorological conditions.In Gurgaon, only the NISE station at Gwal Pahari reported ozone exceedances. The station crossed the standard on four days and recorded a peak eight-hour average concentration of 107 µg/m3. The city’s other monitoring stations at Sector 51, TERI Gram and Vikas Sadan remained compliant throughout the month, recording peak values of 45 µg/m3, 49 µg/m3 and 26 µg/m3, respectively.Unlike PM2.5 and PM10, ozone is not emitted directly from vehicles, industries or other sources. Instead, it forms in the atmosphere when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. High temperatures and intense solar radiation during summer accelerate these chemical reactions, causing ozone levels to rise even when particulate pollution remains relatively low.Of the 30 stations reporting ozone data in Haryana, 18 remained fully compliant throughout May. These included stations in Rohtak, Sonipat, Ambala, Panipat, Panchkula, Nuh, Bhiwani, Charkhi Dadri, Dharuhera, Kaithal and Narnaul, as well as three stations in Faridabad and three in Gurgaon.Nationally, CPCB data analysed by CREA showed ozone pollution to be widespread during May. Of the 510 monitoring stations reporting ozone data across India, 475 had at least 80% data availability. Among these, 154 stations recorded at least one exceedance of the eight-hour ozone standard, while 321 stations remained compliant throughout the month.The analysis found that stations with the highest ozone exceedances were concentrated in Rajasthan, Uttar Pradesh, Delhi, Maharashtra, Madhya Pradesh and Haryana.
