Delhi has directed all government and private schools to hold classes until Class 11 (except Class 10) in hybrid mode - both physical and online - as stricter pollution norms under the Graded Response Action Plan (GRAP) Stage 4 came into effect on Saturday.
Fifty per cent of staff in government and private offices have also been asked to work from home. A similar order was issued on November 24, after GRAP-3 measures came into force, but was withdrawn after the measures were revoked later that month.
The Commission for Air Quality Management (CAQM), the centre's anti-pollution panel, invoked restrictions under GRAP-3 for Delhi and nearby areas on Saturday afternoon and elevated them to GRAP-4 the same evening, noting a worsening in air quality.
The AQI in Delhi was recorded at 431 at 4 pm and rose to 441 at 6 pm.
"Keeping in view the prevailing trend of air quality and in an effort to prevent further deterioration of air quality in the region, the CAQM Sub-Committee on GRAP decides to invoke all actions as envisaged under Stage-IV of the extant GRAP - 'Severe+' Air Quality (DELHI AQI > 450), with immediate effect, in the entire NCR. This is in addition to the actions under Stages I, II & III of extant GRAP already in-force in NCR," the CAQM said in a statement.
GRAP 1 restrictions come into force when the AQI is between 201 and 300 (which is categorised as 'Poor'), GRAP 2 restrictions when it is between 301 and 400 ('Very Poor'), GRAP 3 between 401 and 450 ('Severe') and GRAP 4 when the AQI crosses 450 ('Severe Plus').
Explaining the reasons for the worsening AQI, the CAQM said the feeble Western Disturbance approaching north-west India was the main contributing factor, and not local emissions.
"This prevailing meteorological condition has (resulted in a) marked reduction in wind speed, at times becoming calm, a shift in wind direction from westerly to easterly, and an increase in moisture content in the lower atmosphere. Such conditions during the winter season are conducive to the formation of smog and fog, resulting in poor dispersion and trapping of pollutants near the surface. Owing to these adverse meteorological conditions, a sudden deterioration in air quality has been observed," it said.
