Delhi's AQI hits 468, govt launches GRAP-IV

Delhi's average Air Quality Index (AQI) dropped to the season's worst of 441 at 4 pm on Nov 17, entering the "severe" zone. As the toxic haze persisted over the National Capital Region (NCR), it worsened further, surpassing 450 by 6 pm and entering the "severe plus" category.

In response, the Commission for Air Quality Management (CAQM) decided to implement the fourth and most severe stage of the Graded Response Action Plan (GRAP-IV) in the NCR, starting at 8 am on Nov 18.

Until further notice, all schools will continue classes online. GRAP-IV provides the central and NCR governments the option to allow staff to work from home. "Physical classes will be discontinued for all students, except for Class 10 and 12," said Chief Minister Atishi.

GRAP-IV is activated when air pollution reaches "emergency" levels and the AQI exceeds 450 (on a scale of 500). The primary goal of Stage IV is to reduce pollution by restricting vehicular movement.

This includes prohibiting non-emergency trucks from entering Delhi, including BS-4 and lower diesel-operated medium and heavy freight vehicles, as well as non-BS6 compliant light commercial vehicles (LCVs) registered outside Delhi.

Construction and demolition (C&D) activities on linear public projects, such as roads, highways, flyovers, bridges, power transmission, and pipelines, which were previously exempt, have now been included in the restrictions starting Nov 17.

According to data from the Central Pollution Control Board (CPCB), visibility remained poor throughout the day, causing the AQI to rise sharply. At 9 am, the AQI stood at 421, reaching 452 at 6 pm and spiking to 468 by 10 pm. This marked the fourth 'severe' day of the month.

Prior to this, on Nov 13 at 9 pm, the AQI surged to 454, temporarily staying in the "severe plus" range. Nov 17 saw an AQI of 441, the second-highest this year after 447 on Jan 14.

Anumita Roy chowdhury, Executive Director for Research and Advocacy at the Centre for Science and Environment (CSE), said, "This is happening due to the combined impact of deepening winter inversion and the trapping of high local and regional pollution. Urgent measures are needed to curb further pollution from major sources."

Data from the Decision Support System revealed that stubble burning accounted for 25.2% of Delhi's PM2.5 levels on Nov 16. Unfortunately, the hazardous air is expected to persist for several more days.

"The average AQI for Delhi is expected to remain in the adverse range due to heavy fog, weak winds, and unfavorable meteorological conditions," said CAQM.

According to forecasts from the India Meteorological Department (IMD) and IITM, Delhi's AQI is likely to stay at the higher end of the "severe" or "severe plus" category in the coming days.

GRAP-IV extends the restrictions outlined in Stages 1 to 3. Despite Stage 3's prohibition on building and demolition activities, linear public projects remain exempt—an exemption that was revoked on Nov 17 by the CAQM.

The CAQM advised Delhi and NCR governments to consider enabling public, municipal, and private offices to operate at 50% capacity, with the rest working from home. The central government may also allow its employees to work remotely.

State governments are urged to implement additional emergency measures, such as closing colleges and nonessential commercial activities and potentially introducing an odd-even vehicle rule.

The Meteorological Department reported that hazy conditions, combined with wind speeds of less than 6 km/h from the northwest, prevailed over the region on Nov 17, preventing the dispersion of pollutants.

The lowest visibility of the day was recorded at 500 meters at Palam between 8:30 am and 9 am, while it dropped to just 300 meters at 7 am at Safdarjung, the city’s base station.