The air quality in Delhi deteriorated to the “very poor” category for the first time in three months on Wednesday morning a day after a dusty haze enveloped the National Capital Region (NCR) on Tuesday.
At least 20 of the 38 monitoring stations recorded “severe” category air quality with PM10 (coarser dust particles) being the main pollutant. The highest average Air Quality Index (AQI) of 474 at 8am was recorded at Mundka followed by 460 in Rohini and Bawana.
Delhi recorded an average AQI of 397 (very poor) at 8am on Wednesday. It marked a sharp rise from AQI of 254 (poor) at 4pm on Tuesday. Delhi last recorded “very poor” air quality on February 22 with an AQI of 302.
An AQI between 0-50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor” and over 400 “severe”.
The sky turned virtually white on Tuesday afternoon as strong winds funnelled in sandy particles from the deserts of Rajasthan, and kicked up loose soil and local construction debris.
The primary pollutant on Tuesday was PM10 particles, which are coarser than the more harmful PM2.5 generated mostly as smoke. Its levels reached close to 30 times the safe limits in parts of the city.
Dust particles can irritate the lungs, trigger respiratory problems, and exacerbate existing conditions such as asthma, bronchitis, and allergies.
Westerly winds also brought in dust from Rajasthan, which was reflected in the low visibility of 700 metres on Tuesday. A lack of rain and temperatures in excess of 40°C contributed to the phenomenon.
The pollution episode brought back into the spotlight hazardous air pollution levels, which mostly occur in winter when weak winds trap local pollutants and farm fires bring in toxic smoke. High pollution levels are now also routine in summer when dust storms grip the city. The erosion of the Aravalli range has been blamed among the reasons for it.
The deterioration in air quality on Tuesday prompted the Commission for Air Quality Management (CAQM) in NCR to hold an emergency meeting. The agency said the spike was temporary and the air quality was likely to improve over the next 24 to 48 hours with rain also expected on Thursday.
India Meteorological Department scientist VK Soni, who is part of the CAQM subcommittee, said the air quality is likely to improve to the “poor” category by the end of Wednesday.
Delhi’s average PM10 concentration touched as high 941 micrograms per cubic metre on Tuesday morning. The highest PM10 concentration recorded in the capital was a peak of 3,826 micrograms per cubic metre at Jahangirpuri at 8am. The PM10 concentration touched 2,565 micrograms per cubic metre at 11am on Tuesday, followed by Aurobindo Marg. Such levels can be highly dangerous even for healthy individuals.