Dussehra celebrations triggered a spike in Delhi’s air pollution, pushing the city’s AQI (air quality index) to 244 on Wednesday. This is the highest in 100 days since July 13, when the AQI stood at 246.Dussehra emissions, post-monsoon weather transition, pollution from vehicular emissions and rising farm fires have added to the Capital’s pollution burden, official data and experts suggest.Wednesday’s rise coincided with high particulate matter (PM) levels overnight, with PM10 levels peaking in several areas — the level stood at 488 micrograms per cubic metre in Anand Vihar. On the other hand, PM2.5 level reached 305 micrograms per cubic metre in Punjabi Bagh of West Delhi.Several monitoring stations recorded high particulate matter — solid and liquid particles suspended in air, which can be inhaled and cause serious health problems — concentrations during the intervening night of October 20 and 21, and Wednesday morning. At Okhla Phase 2, PM10 peaked at 469 micrograms per cubic metre at 10 pm on Tuesday.Anand Vihar recorded 488 micrograms per cubic metre at 8 pm, with levels remaining above 450 micrograms per cubic metre through Tuesday night. At Mandir Marg, PM10 reached 410 micrograms per cubic metre at 2 am on Wednesday.PM2.5 levels also rose sharply. Punjabi Bagh recorded a peak of 305 micrograms per cubic metre at 11 pm on Tuesday, while Okhla Phase 2 recorded 269 micrograms per cubic metre at 10 pm.The permissible standards of PM2.5 is 60 micrograms per cubic metre and PM10 is 100 micrograms per cubic metre. Overall, Delhi’s AQI rose from 179 on Tuesday to 244 on Wednesday, while Noida recorded an AQI of 281 and Gurugram 220.Story continues below this adThere are a combination of factors on the rise of pollution during this time of the year.Studies on fireworksStudies conducted in Delhi have documented sharp increases in particulate matter following the use of fireworks during festive season.A 2024 study by IIT Delhi researchers found that during Diwali celebrations, between 2019 and 2021, fireworks accounted for more than 85% of the measured elemental mass in PM2.5 during the festival, after accounting for differences in atmospheric dispersion.As winter approaches, Delhi’s air quality becomes increasingly vulnerable to meteorological conditions that restrict the dispersion of pollutants.Story continues below this adStudies have found that the atmospheric boundary layer, the lowest part of the atmosphere through which pollutants mix, becomes shallower during winter, while night-time temperature inversions can prevent polluted air from rising and dispersing.As per the India Meteorological Department’s (IMD) bulletin “an average wind speed of less than 10 kmph is unfavorable for the dispersion of pollutants.A 2026 study published in Atmospheric Environment journal, researchers affiliated with Physical Research Laboratory (PRL, the Space Applications Centre and the National Centre for Medium Range Weather Forecasting, among others, found that in Delhi between October 2023 and February 2024, the boundary layer remained below 1 km from November to January. Higher PM2.5 concentrations were associated with lower boundary-layer heights.Stubble burningFarm fires in neighbouring states during the paddy harvesting season can add to Delhi’s air pollution, depending on the number and location of fires and whether winds carry the smoke towards the city. According to the Indian Institute of Tropical Meteorology’s (IITM) Decision Support System, used for data analysis, stubble burning contributed around four% to Delhi’s PM2.5 pollution on Wednesday.Story continues below this adTransport emissions accounted for an estimated 21% of PM2.5 pollution and remained the highest pollution source.Farm fires contribution is forecast to rise to 15% by Friday.The Indian Agricultural Research Institute (IARI), which monitors agricultural residue burning using satellite remote sensing, reported 85 detected fire events across seven states and regions on October 21.Between September 15 and October 21, satellites detected 1,350 events across the Northern belt with Punjab totalling to 454, Madhya Pradesh 393, Rajasthan 229, Uttar Pradesh 190, Uttarakhand 72, Haryana 11 and Delhi one.Story continues below this adSunil Dahiya, lead pollution analyst at think-tank Envirocatalysts said, “The winds are coming from the northwest at low speeds of less than 4-5 kmph, which means smoke from the farm fires could be reaching Delhi. From last night, there is clear evidence of a rise in smoke coinciding with the hours of fireworks. Together, these factors have contributed to the increase in air pollution in Delhi.”He added, “This is just the start of the visible pollution in Delhi NCR. The emission loads from fireworks and other regional sources as well as emissions from within Delhi coming from transport, power, industries and other perennial sectors together contribute to this bad air quality season.”