Delhi’s air quality continues to deteriorate with winter setting in, and the trend from October has already set a worrying tone for November. According to data analysed by the Centre for Research on Energy and Clean Air (CREA), the city experienced 27 polluted days last month, with the Air Quality Index (AQI) consistently oscillating between the poor and very poor categories. Only four days were deemed “satisfactory”, and not a single day fell in the “good” category.

An AQI between 51–100 qualifies as satisfactory, while an AQI below 50 is considered good. Delhi saw neither — signalling the capital’s persistent struggle against toxic air.

The worst air quality day was recorded on October 30, with the AQI rising to 373 — the highest October reading in the past three years. Officials also reported irregularities, including under-reporting at CPCB stations and alleged water sprinkling near monitors to influence pollution readings. Despite such attempts, the city still recorded severe pollution, including an AQI of 345 on Diwali night, higher than the 328 recorded on Diwali in 2024.

Analysts say the long-term trajectory remains bleak.

“Between 2015 and 2025, October’s average AQI in Delhi has fluctuated between 173 to a high of 285. Yet the overall trend reveals stagnation rather than progress. The sharp dip in 2021 (AQI 173) was an anomaly caused by COVID-19 lockdowns that temporarily reduced baseline emissions, not a lasting improvement,” said Manoj Kumar, analyst at CREA.

With winter expected to trap pollutants further and crop-burning season underway in neighbouring states, experts warn that Delhi may be on course for yet another hazardous pollution season unless urgent mitigation measures are intensified.