The level of particulate matter (PM) 2.5 went down by about 15 notches this weekend compared to the last weekend. While PM2.5 was recorded at 131.53 g/m3 (micrograms per cubic metres) on January 3, it came down to 114.50 g/m3 on Sunday.

On Saturday, PM2.5 was recorded at 119 g/m3, four points less than what it was last Saturday. However, the level continues to be much higher than the safe standard of 60 g/m3.

The level of carbon monoxide has also gone down slightly. It was recorded 1.73 g/m3 and 1.52 g/m3 last Saturday and Sunday, respectively. On Sunday, January 10, the level of carbon monoxide was recorded at 0.85 g/m3.

While experts credit a decrease in the number of vehicles on roads for bringing down PM2.5, officials of HSPCB (Haryana State Pollution Control Board) held weather forces responsible for the fluctuation. "It seems Delhi's odd-even scheme has helped keep the concentration of PM low in the NCR atmosphere. If we compare the figures with last winter, when PM2.5 levels in the city went up to about 140 g/m3, the situation seems better this year. City authorities, however, need to come up with more measures to bring down air pollution. Sometimes, it takes time to see actual results of any anti-pollution measure," said Debjani Ghosh, a city-based environmentalist.

An official of HSPCB, on the other hand, told TOI, "Along with the level of most suspended particles in the air, the level of PM2.5 keeps fluctuating due to various factors, including wind speed, amount of fog, humidity, sunlight and most importantly temperature. I don't think there was a definite fall, rather there was a mere fluctuation in the PM2.5 level."