Gurgaon: With low wind speeds and a drop in temperature, the city's air quality worsened on Saturday recording an air quality index (AQI) of 198, up from 168 on Friday. While the air quality remained ‘moderate' for the fifth time this month, it was just a few points shy of being in the ‘poor' category.
Of the four monitoring stations in the city,
Teri Gram recorded the worst AQI at a 'poor' 218, followed by Sector 51 (213), Gwal Pahari (200) and Vikas Sadan (175).
Following the Supreme Court's revocation of GRAP 4 on Dec 5, the region is currently under GRAP 2, under which residents are advised to limit the use of private vehicles and follow guidelines regarding the operation of diesel generators. On Saturday, the city's wind speed plummeted to 3 kmph from 7 kmph the previous day.
The System of Air Quality and Weather Forecasting and Research (Safar) predicted that pollution levels in NCR will continue to worsen over the next six days, with AQI expected to reach the ‘poor' and ‘very poor' categories.
Safar also noted that wind speeds below 3 kmph would lead to airborne pollutants remaining suspended in the air, exacerbating the pollution levels.
The levels of PM2.5, toxic particles that can penetrate into the lungs and enter the bloodstream, also increased, HSPCB said. While the permissible PM2.5 limit is 60 µg/m³, the levels at Teri Gram rose from 123 µg/m³ on Friday to 308 µg/m³ on Saturday. At Sector 51, PM2.5 increased from 264 µg/m³ to 321 µg/m³, while at Vikas Sadan, it went from 148 µg/m³ to 220 µg/m³. At Gwal Pahari, the level jumped from 130 µg/m³ on Friday to 318 µg/m³ on Saturday. PM2.5 can lead to serious health conditions such as asthma, stroke, and heart and lung diseases.
HSPCB officials have pointed out that localised factors, especially dust from unregulated construction activities and unpaved roads contribute majorly to the city's poor air quality. "Dust is a primary cause of pollution, and we will take measures to reduce it," said Vijay Chaudhary, the regional officer of HSPCB. Air pollution has become a year-round problem for Delhi-NCR, especially during the winter, when adverse weather conditions trap pollutants in a toxic haze.
The Graded Response Action Plan (GRAP) in NCR categorises the AQI into four stages: stage 1 (poor) for AQI between 201-300, stage 2 (very poor) for AQI between 301-400, stage 3 (severe) for AQI between 401-450, and stage 4 (severe+) for AQI above 450. Actions for stages 2, 3, and 4 are triggered at least three days in advance based on dynamic forecasts and meteorological predictions.
Meanwhile, the air quality of Delhi deteriorated on Saturday with the Air Quality Index (AQI) reaching 233 in the ‘poor' category after staying in the ‘moderate' range for three consecutive days. The overall air quality of Delhi is predicted to remain ‘poor' on Sunday and Monday, but it may worsen further to ‘very poor' on Tuesday.
Delhi's AQI significantly improved earlier this week after strong winds started blowing in the city. The AQI was 178 on Dec 4, 165 on Dec 5 and 197 on Dec 6. Winds with high speed cause the dispersion of pollutants, while calm winds cause the accumulation of pollutants. "Light winds of 4 to 8 kmph blew during the daytime on Saturday, impacting the air quality. However, the winds turned calm during the evening. Similar conditions are likely to persist over the next two days," said Mahesh Palawat, vice-chairman, Skymet Meteorology.
Apart from winds, low temperatures and inversion impacted the ventilation. The city recorded the season's lowest minimum temperature of 7.1 degrees Celsius on Saturday, three degrees below normal for this time of the year. "Mainly clear sky conditions with wind speed less than 10 kmph northwest direction prevailed over the region in the forenoon on Saturday," said India Meteorological Department in its bulletin.
Two stations—Shadipur and Anand Vihar—even saw ‘very poor' AQI throughout the day with readings of 317 and 310, respectively, at 4 pm, shows Central Pollution Control Board's data.
In the neighbouring cities, Greater Noida also recorded poor air quality with an AQI of 218.
However, AQI remained in the ‘moderate' category at Noida (179), Ghaziabad (175), Gurgaon (198) and Faridabad (199).
According to the Air Quality Early Warning System for Delhi, which is the forecasting body under the Union ministry of earth sciences, the air quality is likely to remain ‘poor' on Sunday and Monday, but may reach the ‘very poor' band on Tuesday. At present, measures under stages I and II of the Graded Response Action Plan are in force.
An AQI reading of 50 or below is classified as ‘good', while readings between 51 and 100 fall in the ‘satisfactory' category, and those between 101 and 200 are classified as ‘moderate'. ‘Poor' air ranges from 201 to 300, ‘very poor' from 301 to 400, and ‘severe' from 401 to 500.
Supreme Court on Thursday asked the Commission for Air Quality Management that Grap-3 should be imposed immediately if AQI goes above 350 and Grap-4 should kick in if it crosses 400.
In Dec so far, Delhi has witnessed four ‘poor' and three ‘moderate' days. The favourable meteorological conditions have kept AQI low in Dec till now. This Nov was the second most polluted penultimate month ever after 2021.