Grap 4 anti-pollution curbs in play as AQI hits season's peak

A thick, grey haze cloaked Delhi on Sunday, smudging out silhouettes as the air quality index (AQI) surged to the season's highest and sent authorities scrambling to contain the devolving crisis, with the Commission for Air Quality Management (CAQM) ushering in Stage 4 of its pollution control measures that ban all constructions and allow schools to call off classes for most students.

- Jasjeev Gandhiok

The Capital clocked a 24-hour average AQI of 441 (severe) on Sunday, according to the Central Pollution Control Board's (CPCB) 4pm bulletin.

This was worse than the 417 reading at the same time on Saturday, even as the air quality continued to slide towards the far reaches of the "severe" zone through the evening. At 7pm, the AQI worsened to 457, the worst hourly reading yet this year.

At 12am on Monday, the AQI touched 474. CPCB classifies an AQI over 400 as "severe".

Weather scientists pinned the deterioration to the increased influx of fumes from farm fires in Punjab, where farmers are ratcheting up blazes to clear out their fields ahead of the winter crop. These thick, black fumes, scientists said, were being swept into Delhi and the National Capital Region (NCR) by strong transport winds and being trapped close to the ground by sluggish surface winds.

AQIS of this level can trigger severe respiratory and cardiac illnesses even in healthy people, while exposing the elderly and immunocompromised to lifethreatening hazards, warned experts.

Meanwhile, scientists also warned of the formation of "super fog" around Delhi-NCR, with the India Meteorological Department (IMD) issuing an orange alert for Monday, warning of severely impaired visibility.

CAQM, a central agency tasked with controlling pollution in the National Capital Region (NCR), convened an emergency meeting on Sunday evening as the crisis grew more acute.

Measures under Stage 4 of the Graded Response Action Plan (Grap) will come into effect from 8am on Monday, said the agency, with forecasts predicting no significant change in weather conditions.

Stage 4, the strictest measures under Grap, open the door for state governments to implement the "odd-even" rationing plan for private cars.