Delhi's air quality enters 'severe plus' category

Delhi's air quality plunged into the 'severe plus' category on Thursday, with a 24-hour average Air Quality Index (AQI) of 451 recorded at 4 pm, according to the Central Pollution Control Board data.

The city witnessed dangerously high levels of PM2.5, the primary pollutant, with 32 of the 35 monitoring stations recording air quality in the severe plus category.

Some areas recorded AQI readings as high as 470. The PM2.5 particles, measuring 2.5 micrometres or less in diameter, pose significant health risks as they can penetrate deep into the lungs when inhaled.

The national capital remains under Stage IV of the Graded Response Action Plan (GRAP), which includes the most stringent anti-pollution measures.

The measures involve a complete ban on construction activities and the entry of non-essential polluting trucks into the city.

GRAP 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).

The Indian Meteorological Department has issued a yellow alert for Friday, warning a very dense fog. The maximum temperature on Thursday was recorded at 23 degrees Celsius, slightly above the season's normal, while the minimum temperature was five degrees Celsius, three notches below normal, the department said.