GRAP Stage 4 curbs invoked in Delhi as air quality turns 'severe'

New Delhi: The Centre's air quality panel for Delhi-NCR on Monday imposed the strictest Stage 4 curbs under the winter air pollution control plan, including a ban on all construction activities, as the region's air quality deteriorated to 'severe' due to unfavourable weather conditions.

Stage 4 curbs under the Graded Response Action Plan (GRAP) for winters also include a ban on the entry of polluting trucks carrying non-essential goods into Delhi and mandatory shifting of school classes, except those for X and XII, to hybrid mode.

Delhi's 24-hour average Air Quality Index (AQI), which was 379 at 4 pm, breached the 400 mark around 10 pm amid extremely calm wind conditions and the buildup of an inversion layer, which adversely affects the vertical mixing height – the height up to which pollutants can disperse.

The decision to impose Stage 4 curbs came just hours after the Commission for Air Quality Management (CAQM) implemented restrictive measures under GRAP Stage 3, following Delhi's AQI breaching the 350 mark in the afternoon.

According to the revised GRAP schedule, classes for students in grades VI-IX and XI in Delhi, Gurugram, Faridabad, Ghaziabad and Gautam Buddh Nagar must operate in hybrid mode (physical and online) under Stage 4.

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.

Stage 4 also includes a ban on all construction and demolition activities, including public projects like highways, flyovers, power lines, and pipelines. Non-essential diesel trucks are prohibited from entering Delhi.

Public, municipal, and private offices must decide on allowing only 50 per cent of staff to work in offices, with the remaining staff working from home. States may consider additional measures like closing colleges, non-essential businesses and implementing odd-even vehicle restrictions.

Under Stage 3, imposed earlier in the day, 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.

The Delhi and NCR state governments have been asked to stagger timings for public and municipal offices under Stage 3. The Centre may consider similar measures for its offices in Delhi-NCR.

During winters, Delhi 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).

GRAP 4 was invoked in Delhi for the first time this season in November due to consistently high pollution levels in the city and adjoining areas.

The Supreme Court allowed the CAQM to relax the curbs in the first week of December after the city's air quality improved.

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.

Prolonged exposure to high pollution levels can exacerbate respiratory issues such as asthma, bronchitis and chronic obstructive pulmonary disease (COPD) and significantly increase the risk of cardiovascular diseases, according to doctors.