New Delhi, Dec 15 (IANS) The air pollution situation in the NCR was worse this year against the situation in the peak season last year though Diwali was less polluting, the Central Pollution Control Board (CPCB) said here on Friday.

In Delhi, the peak pollution episode between November 7 and 12, 2017 saw the range of major pollutant PM2.5, or particles in air with diameter less than 2.5 micrometers, to be around 357 to 611, according to the CPCB.

However the same ranged between 197 to 709 in 2016 peak pollution time -- between October 30 and November 7.

Meanwhile, pollutant from fire crackers saw considerable drop -- Diwali (on October 19 this year) saw 39.3 per cent decrease in PM2.5 level against Diwali in 2016 (October 30).

The CPCB believes the Supreme Court's ban order on sale of fire crackers this year in National Capital Region is the major reason behind this.

"It was a good Diwali for us in a bad season... Supreme Court played a very good role," said D. Saha, Divisional Head, CPCB.

The experts at the apex pollution monitoring agency believe meteorological factors such as low wind speed, temperature together with high humidity and a high mixing height during the peak of 2017 pollution episode, against 2016, is the reason that air quality this year was more toxic.

"Wind speed in 2016 was 1.0 to 3.0 mps, while this year it was 1.0 to 1.3 mps, the relative humidity in 2016 was 47.8 to 63.3 per cent against 60.2 to 75.8 per cent this year. At the same time, mixing height was 146 to 618 metres in 2016 against 336 to 479 metres this year," said Saha.

Pollutants do not disperse easily with low winds or high mixing height, while high humidity levels also increases their density.

"Lessons that we learned was that this particular period is critical for us," Saha said.

The CPCB also saw a drop in the concentration of highly toxic elements since Diwali 2016. The element include aluminium (9.9 per cent drop), sulphur (20.1), chlorides(11.0), potassium (29.9), calcium(37.8), iron(48.1), copper(36.3), zinc(41.1), strontium (64.6), antimony (35.6) and barium (51.7) -- all used in the fire crackers, either for making a bang, throttling, or colour.

"All the elements except titanium saw a drop, as there was little bit rise in the Titanium which we are still trying to find out why," the CPCB scientists said.

"For instance, PM2.5 level in Pitampura during Diwali 2016 was 1,238, while after Diwali 2017, it was 677, same goes the trend in other areas and factors like elements coming from fireworks," Saha said.

The official however added that while Delhi has its own emissions, the effluents like dust or burning from the neighbouring areas keep the pollution levels up.

"Even on normal days, Delhi gets 30 per cent pollutants from other areas," Saha said.