Delhi’s sharp rise in air pollution after Diwali was primarily driven by firecracker emissions, according to an assessment by the Indian Institute of Tropical Meteorology (IITM). The study estimated that fireworks contributed more than 80% of the capital’s pollution load on the day after Diwali, with their share in PM2.5 levels reaching over 71% between 1 am and 9 am on November 9. By comparison, firecracker emissions accounted for only a small fraction of PM2.5 in the days leading up to the festival, highlighting the significant impact of festive celebrations on air quality.

The assessment also showed that other pollution sources played a much smaller role during the peak pollution period. Vehicular emissions contributed 6.9% of PM2.5, while secondary inorganic aerosols and secondary organic aerosols accounted for 5% and 4.5%, respectively. Although Delhi’s Air Quality Index (AQI) gradually improved after Diwali due to stronger winds dispersing pollutants, it remained in the “very poor” category for several days. Pollution readings at some monitoring stations briefly reached extremely high levels before later being revised by authorities.

However, the findings have sparked debate, with trade representatives arguing that firecrackers have only a temporary impact and that other major pollution sources, including stubble burning and seasonal weather conditions, must also be addressed. Health experts, meanwhile, warned that prolonged exposure to high PM2.5 levels can trigger respiratory illnesses and increase the risk of heart attacks, strokes, and other cardiovascular emergencies, underscoring the serious public health consequences of severe air pollution.