The Centre's panel on Delhi-NCR's air quality on Thursday re-implemented stage 3 curbs under the Graded Response Action Plan amid a sharp rise in air pollution levels owing to unfavourable meteorological conditions, according to an official order.

Delhi's air pollution levels showed an increasing trend and the 24-hour average air quality index (AQI) stood at 357 at 4 pm, up from 297 on Wednesday, owing to "calm winds and foggy conditions".

The Commission for Air Quality Management, responsible for strategising air pollution mitigation in Delhi-NCR, directed authorities in the region to immediately implement curbs prescribed under stage 3 to prevent further worsening of the situation.

GRAP Stage 3, which was revoked on Sunday, entails a ban on non-essential construction work.

Classes up to grade V are required to shift to hybrid mode under Stage 3. Parents and students have the option to choose online education wherever available.

Under Stage 3, the use of BS-III petrol and BS-IV diesel cars (4-wheelers) is restricted in Delhi and nearby NCR districts. Persons with disabilities are exempt.

Stage 3 also bans non-essential diesel-operated medium goods vehicles with BS-IV or older standards in Delhi.

During winters, the Delhi-NCR region enforces restrictions under GRAP, which categorises air quality 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 above 450).

Unfavourable meteorological conditions, combined with vehicle emissions, paddy-straw burning, firecrackers, and other local pollution sources, lead to hazardous air quality levels in Delhi-NCR during winters.

Doctors say that breathing Delhi's polluted air is equivalent to smoking approximately 10 cigarettes a day.

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