New Delhi: The air quality deteriorated further on Tuesday as the air quality index rose to 433 in the severe category, with a toxic haze enveloping the city. It was the worst air quality in almost a month — a higher AQI than this was last recorded on Nov 19 at 460.
The air quality is likely to stay severe on Wednesday, but it may improve to very poor on Thursday. However, the Met department has placed a yellow alert for moderate to dense fog over the next three days. On early Tuesday, Delhi saw moderate fog with the lowest visibility of 350 metres at Safdarjung, the city’s base station.
Meanwhile, the minimum temperature on Tuesday rose to 5.9 degrees Celsius, two degrees below normal, compared to 4.5 degrees Celsius on Monday. No station saw cold wave conditions. The maximum temperature settled at 24.5 degrees Celsius, one notch above normal.
Delhi witnessed a sharp decline in air quality in the past 48 hours after winds turned calm and there was the formation of shallow to moderate fog. Central Pollution Control Board’s data shows that AQI was 379, very poor, at 4pm on Monday, but it rose to 401 in the severe range at 10pm.
On Monday, Commission for Air Quality Management imposed measures under stage III of Graded Response Action Plan during the day. However, after AQI surpassed 400 in the night, stage IV was invoked with immediate effect. It bans the entry of non-essential trucks running on non-cleaner fuel and stops construction activities in linear public projects such as highways, roads, flyovers, overbridges, power transmission and pipelines.
Experts said no improvement in the air quality was expected on Wednesday. “As winds have slowed down since Monday, it is hampering the process of dispersion of pollutants. Due to a western disturbance, which is currently impacting northwest India, there has been a rise in humidity levels, leading to the formation of shallow to dense fog. Fog also traps pollutants,” said Mahesh Palawat, vice-president of Skymet Meteorology.
Similar conditions are likely to persist on Wednesday, but the wind speed may rise on Thursday after the influence of the western disturbance is over, he added.
This Nov recorded eight severe days, including two severe-plus, when AQI crossed 450, and 22 very poor days. It also witnessed AQI reaching 494 on a scale of up to 500 on Nov 18, making it the second most polluted day ever. In comparison to Nov, the first fortnight of Dec was relatively better than the past year.
Anumita Roychowdhury, executive director of research and advocacy at Centre for Science and Environment, said, “We know from past experience that more pollution spikes happen during the second half of winter — after the crop burning season is over — due to the intensification of cold and calm conditions. This indicates high and elevated levels of pollution in the city and the region.”
Pointing out that the annual average and the winter average of PM2.5 levels took an upward curve last year, she emphasised that action must be ramped up to ensure Delhi continues to reduce the annual average level.
