Districts in southern Haryana, including Faridabad, Palwal, Sonipat, Panipat and Gurugram, record the highest concentration of secondary particulate matter in the state, significantly contributing to year-round PM2.5 spikes, according to the latest analysis by the Centre for Research on Energy and Clean Air (CREA).
The assessment, based on NASA’s MERRA-2 reanalysis data for 2024, found that ammonium sulphate makes up around one-third of the annual PM2.5 mass across most Haryana districts, accounting for about 29.4% to 33.9% of the total PM2.5 composition recorded during the year.
In Gurugram, secondary particulate matter accounted for around 32.6% of the annual PM2.5 load, translating to a mean concentration of approximately 19 µg/m³ in 2024, the analysis showed. Comparable ammonium sulphate concentrations were recorded in Faridabad at 19.75 µg/m³, Palwal at 18.93 µg/m³, Sonipat at 19.11 µg/m³ and Panipat at 18.24 µg/m³, all within the ~30–34% range of annual PM2.5 values.
“Air pollution in many of these districts is driven by atmospheric chemical reactions, other than primary sources. Without reducing precursor gases through mitigation measures and regional coordination, improvements in air quality are likely to remain short-lived,” said an analyst at CREA.
Experts said the elevated presence of ammonium sulphate indicates that a substantial portion of air pollution in these districts is not directly emitted but formed chemically in the atmosphere from precursor gases.
CREA’s analysis also found that nearly one-third of Haryana’s annual PM2.5 load is secondary ammonium sulphate. Its contribution rises sharply during high-pollution periods, accounting for 49% of PM2.5 in the post-monsoon season and 40% in winter, compared with 18% in summer and 19% during the monsoon.
“This shows that the southern Haryana districts, particularly Gurugram and Faridabad’s worst pollution episodes, are driven largely by region-wide SO2 emissions and secondary formation, not only local primary sources,” said Dr Manoj Kumar, an analyst at CREA.
The districts with the lowest ammonium sulphate presence in PM2.5 were Panchkula at around 11.68 µg/m³, Yamunanagar at 11.98 µg/m³, Ambala at 12.68 µg/m³ and Kurukshetra at 15.59 µg/m³, the analysis showed.
Kumar said PM2.5 forms 40–60% of the particulate load in metro cities during winter and is significantly more toxic than PM10. “Being in proximity to Delhi, Gurugram air quality levels, particularly PM2.5 concentrations, remain staggeringly high, particularly during peak and night hours when illegal burning of waste mostly takes place,” he said.
According to the World Health Organisation, prolonged exposure to high PM2.5 levels can cause respiratory illnesses such as asthma and bronchitis and increase the risk of heart disease. The particles, which are at least 33 times smaller than a human hair, can penetrate deep into the lungs and enter the bloodstream, causing long-term health damage, experts warned.