Delhi Air Has Highest Mercury Levels Among 3 Cities; Traffic, Stubble Burning Blamed

Delhi’s peak values were found to be nearly 13 times higher than the natural background. Researchers attributed 72–92% of mercury emissions in these cities to human activities.

Delhi has recorded the highest concentration of mercury in the air among three Indian cities, according to a six-year study by the Indian Institute of Tropical Meteorology (IITM), Pune. The toxic metal, linked to neurological, kidney and heart problems, was found to be well above natural background levels in Delhi, Ahmedabad and Pune, with coal, traffic and industries identified as major sources.

Published in the journal Air Quality, Atmosphere & Health (Springer), the study analysed air samples between 2018 and 2024, focusing on gaseous elemental mercury. It reported average concentrations of 6.9±4.2 nanograms per cubic metre (ng/m³) in Delhi, compared with 2.1±0.7 ng/m³ in Ahmedabad and 1.5±0.4 ng/m³ in Pune. The global background level is around 1.7 ng/m³ in the Northern Hemisphere.

Human Activities Blamed For High Mercury Levels 

Delhi’s peak values were found to be nearly 13 times higher than the natural background. Researchers attributed 72–92% of mercury emissions in these cities to human activities. Seasonal and winter spikes in Delhi and Ahmedabad were linked to coal use, stubble burning, and stagnant atmospheric conditions.

While the study noted a declining trend in Delhi’s mercury levels compared to earlier years, the capital still remains among the highest in South Asia.

“Mercury is among the top 10 chemicals of major public health concern, according to WHO. Even in small amounts, if exposure continues for 5–10 years, it can be dangerous. Long-term inhalation mainly affects the nervous system, digestive system, immune system, kidneys and lungs,” said Gufran Beig, chair professor at the National Institute of Advanced Studies, IISc.