Delhi air quality report highlights severe winter pollution trends

A seven-year IIT Kanpur study (2017-2023) reveals Delhi’s PM 2.5 levels peak during October-January, with air quality consistently in the ‘very poor’ category. Pollution severity rises sharply after sunset, with the worst conditions between 10 pm and 11 am. November and December show the highest concentrations, exceeding 250 µg/m³ during up to 40% of daily hours.

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A seven-year analysis of air quality in Delhi (2017-2023) highlights a marked increase in PM 2.5 levels from October to January annually, with concentrations peaking in mid-November. According to the October 2024 IIT Kanpur report, air quality during this period consistently falls into the ‘very poor’ category over 24 hours, with the worst conditions observed from 10 pm to 11 am. The report suggests that 1 pm to 7 pm is the most suitable time for outdoor activities, even for schoolchildren, if required.

“It is to be noted that pollution starts to pick up in Week 4 of October and the highest severity is observed in the second and third weeks of November. The pattern continues into December, where pollution remains high, particularly during the late night and early morning hours,” states the report titled ‘Delhi’s PM 2.5 levels (2017-2023) Probabilistic Analysis of Air Quality and AQI categories for personal and community intervention.’ It emphasizes early enforcement of control measures before November to mitigate pollution levels.

Based on data from Sirifort, Mandir Marg, Sonia Vihar, and Dilshad Garden, the study reveals a “pronounced increase in PM2.5 concentrations” during winter months, especially October to December. PM 2.5 levels remain below 100 from mid-February until October, dipping to under 50 during July-September, but escalate to over 200 from October to December. November and December see severe pollution levels exceeding 250 µg/m³ during 40% of day hours in early November and 35% by mid-December. The report notes, “These findings emphasize the importance of targeted interventions during the high-pollution winter period to mitigate health risks and improve air quality in Delhi.”

While summer months experience lower pollution due to wind and rainfall aiding dispersion, winter’s poor air quality, especially at night, results from reduced temperatures and limited atmospheric dispersion.