The Centre's pollution control panel on Thursday issued directions to ban non-essential construction work in Delhi-NCR and the entry of diesel-guzzling trucks into the capital as the air quality in the city entered the 'severe' category.

This action comes as part of Stage III of the Graded Response Action Plan (GRAP) -- the Centre's air pollution control plan that is implemented in the region during the winter season.

Delhi's Air Quality Index (AQI) stood at 402 at 5 pm.

At a meeting to review the air quality situation in Delhi-NCR, the Commission for Air Quality Management (CAQM), a statutory body responsible for developing strategies to combat pollution in the region, said that the pollution levels are only "expected to increase further" owing to unfavourable meteorological and climatic conditions.

GRAP categorises actions into four stages: Stage I - 'Poor' (AQI 201-300); Stage II - 'Very Poor' (AQI 301-400); Stage III - 'Severe' (AQI 401-450); and Stage IV - 'Severe Plus' (AQI >450).

Stage III of GRAP involves a complete halt on construction and demolition work except for essential government projects, mining and stone crushing.

It also includes a ban on the entry of light commercial vehicles registered outside Delhi and diesel-guzzling trucks, and medium and heavy goods vehicles (except those involved in essential services).

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