Crackers unleashed, toxic haze cloaks city

Delhi's first Diwali with legal firecrackers in years delivered the worst air pollution spike since 2021, with fine particulate matter concentrations hitting levels that would register an air quality index of 812 — if the official scale weren't capped at 500 — despite warmer temperatures and fewer farm fires that should have kept the air cleaner.

- Abhishek Jha and Jasjeev Gandhiok

The official 24-hour average air quality index calculated at 4pm on Tuesday stood at 351, slightly worse than 345 the previous day — but this bulletin masks the rapid accumulation of pollutants during firecracker bursting.

Average PM2.5 concentrations — ultrafine particles 2.5 microns or less in diameter — across eight stations with consistent historical data peaked at 785.6 micrograms per cubic metre (ug/m3) this Diwali, the highest since 2021 when it was 772.9 ug/m3. In AQI terms, 2021's levels compute to 802.

Among the most intense readings were in Nehru Nagar, abutting Lajpat Nagar, where PM2.5 levels surged to 1,763 micrograms per cubic metre (ug/m’) for an hour on average till 10pm. At East Delhi's Anand Vihar, this figure was 1,710 uig/m? till lam. Both readings were nearly 29 times the safe limit of 60 ug/m’.

Data suggests meteorological providence-warmer temperatures and moderate winds on the morning after-helped blow away some of the Diwali pollutants. To be sure, a reading of 351 still qualifies as "very poor"-a category for which the National Centre for Disease Control (NCDC) recommends "avoiding physical activity outdoors" and remaining indoors as far as possible.

PM2.5 ultrafine particles are mostly the by-product of any combustion, and they can reach deep into lungs, enter the bloodstream, and lead to immediate illness such as asthma and bronchitis as well as long-term cardiovascular ailments. On October 18, the Supreme Court allowed "green firecrackers" on a trial basis to "balance religious celebrations with public health". The court imposed strict time restrictions-8pm to 10pm on Mondaybut those limits were widely violated. The ruling also mandated close monitoring of firecracker emissions.