Gurgaon: Haryana has emerged as one of India's growing ozone hotspots, with ground-level ozone becoming a significant air quality concern even as particulate pollution remained relatively low during May. Data from the Central Pollution Control Board's (CPCB) continuous ambient air quality monitoring network reveals that 12 of the state's 30 monitoring stations breached national standards for ozone during the month.
Ozone Concentration Levels in Haryana
Nathu Colony in Ballabgarh recorded the seventh-highest ground-level ozone concentration in India in May, with a maximum eight-hour average of 278 micrograms per cubic metre (µg/m³), nearly three times the National Ambient Air Quality Standard (NAAQS) of 100 µg/m³. Nationally, the highest ozone concentration 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, ahead of stations in Moradabad, Tonk, and Sri Ganganagar.
Exceedance Days Across the State
CPCB data analysed by the Centre for Research on Energy and Clean Air (CREA) shows that 40% of Haryana's monitoring stations reported at least one day when the maximum rolling eight-hour ozone concentration exceeded the NAAQS. F-Block in Sirsa recorded the highest number of exceedance days, with ozone levels crossing the limit on 13 days in 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 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 (two exceedance days each), Police Lines in Jind and IMT Manesar (two each), and stations in Karnal, Kurukshetra, and Ballabgarh (one 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.
Regional and National Trends
Unlike particulate pollution, which is often concentrated near emission sources, ozone can travel long distances and affect areas far from where its precursor pollutants are emitted. This makes ozone a regional air quality challenge requiring coordinated action across sectors and districts. Manoj Kumar, an analyst at CREA, 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." He added that the pattern indicates ozone pollution is not confined to major urban centres and can affect peri-urban and semi-urban regions as pollutants are transported under favourable meteorological conditions.
Nationally, CREA's analysis of CPCB data found ozone pollution widespread during May. Of 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. Stations with the highest ozone exceedances were concentrated in Rajasthan, Uttar Pradesh, Delhi, Maharashtra, Madhya Pradesh, and Haryana.
Health and Environmental Impacts
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. Ozone can also damage crops and natural vegetation. 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.
Gurgaon and Compliant Stations
In Gurgaon, only the NISE station at Gwal Pahari reported ozone exceedances, crossing the standard on four days with 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. Of the 30 stations reporting ozone data in Haryana, 18 remained fully compliant in May, including stations in Rohtak, Sonipat, Ambala, Panipat, Panchkula, Nuh, Bhiwani, Charkhi Dadri, Dharuhera, Kaithal, Narnaul, three in Faridabad, and three in Gurgaon.
The findings underscore the rise of ozone as a growing summer air quality challenge across Haryana, even as particulate pollution levels ease after winter. The state may increasingly need to address ozone pollution during the summer months, requiring coordinated action across districts and sectors.
