If Delhi breathed a little easier in the first half of January due to relatively warmer days and, to some extent, the odd-even traffic restrictions, the late onset of winter chill has made the second half more polluted.
On Friday, as the city woke up to the season’s coldest morning yet with the minimum temperature a frigid 4.2 degrees Celsius, three below normal, pollution levels were up despite good wind speed. The maximum was 17.7ºC, four notches below normal.
The National Air Quality Index at three out of four stations that measure particulate matter 2.5 and 10 — tiny particles that penetrate and lodge deep in the lungs and put one at risk of cancer and respiratory disorders — showed ‘severe’ readings, the highest level. These stations are at Anand Vihar, Punjabi Bagh and RK Puram. The reading at the fourth station, in Mandir Marg, was a notch lower at ‘very poor’. The air quality may stay the same for the next five days with temperatures expected to remain in the 5-19ºC range.
According to the Centre for Science and Environment, the gains in terms of reduction in air pollution made during the odd-even trial run have been lost completely and the cold weather has made things worse.
Pollutants accumulate near the earth’s surface when temperatures are low and humidity high, a condition prevalent since January 14. Dense fog has added to the problem, lowering visibility in the mornings but more importantly, trapping the pollutants.
The wind speed was in the range of 2 and 4 meters per second on Friday. But while the same speed last week was effective in dispersing pollutants during the odd-even days, it didn’t have much of an impact on the air quality through the day.