SPATIOTEMPORAL VARIABILITY, EMISSION SOURCES AND METEOROLOGICAL CONTROLS OF PM2.5 AND PM10 IN DELHI, PUNJAB, HARYANA AND CHANDIGARH: A COMPARATIVE REVIEW (2018–2026)

Abstract

Delhi, Chandigarh, Haryana and Punjab lie in the north-western Indo-Gangetic Plain (IGP), one of the most polluted regions in the world. This review synthesizes outdoor PM2.5 and PM10 evidence for these four jurisdictions published between 2018 and 2026, drawing on national monitoring analyses, city-level records for Delhi and Chandigarh, and state wide, district and site-level studies for Punjab and Haryana. Across the jurisdictions reviewed, mean PM2.5 ranged from about 51 to 118 µg/m³ and PM10 from about 76 to 225 µg/m³ – 1.3–3.0 and 1.3–3.8 times the national standards – and no city, district or network mean met either annual standard. In Delhi, PM2.5 averaged 83–101 µg/m³ and PM10 164–225 µg/m³ during 2018–2024 (CPCB January–November means), with 157–206 “poor” to “severe” AQI days a year and no sustained decline after 2020. Punjab's two continuous sites averaged 58–73 µg/m³ PM2.5 over 2017–2023, below Delhi's 105–118 µg/m³, but Ludhiana was the only monitored site in the four jurisdictions with a significant upward trend (almost 10% a year). Haryana's district monitoring data for 2019–2024 averaged 64 µg/m³ PM2.5 and 145 µg/m³ PM10; at least 20 of 23–24 locations exceeded the annual PM2.5 standard every year from 2021, and the NCR hotspots of Gurugram, Faridabad and Charkhi Dadri (85–95 µg/m³) now approach Delhi. Even Chandigarh, a planned city with extensive green cover, recorded annual PM10 of 76.2 µg/m³ in 2020 and 91.7 µg/m³ in 2021 at its Sector 25 station, above the 60 µg/m³ standard, with October peaks of about 121–125 µg/m³ during paddy-residue burning. During the 2020 COVID-19 lockdown, PM2.5 fell by about 43% in Punjab relative to the pre-lockdown weeks and by 57% in Haryana relative to the same period of 2019; this indicates a large anthropogenic share, although favourable spring meteorology also contributed, and Haryana's PM10 in the same spring window had returned to its pre-pandemic level by 2022. Winter meteorology, crop residue burning, traffic, industry and dust drive these patterns, and nearly half of Haryana's PM is transported from outside the state. We conclude that sustained improvement in northern Indian air quality requires airshed-wide coordination across Delhi, Punjab, Haryana and Chandigarh, enforcement of NCAP city plans, alternatives to stubble burning and expanded monitoring beyond large cities.