New Delhi, Dec 6: The 'milky white' nature of fog and associated haze that has shrouded Delhi with the onset of winter show that pollution has not yet spiked to last year's level, a top expert said, indicating that the worst is yet to come.
The city's air quality, that "became better" post Diwali and then fell around November 26, has largely oscillated between 'very poor' and 'poor', with pockets where it is 'severe', chief project scientist of System of Air Quality and Weather Forecasting And Research (SAFAR) Gufran Beig said.
"Levels of PM 2.5 touched 130 micrograms per cubic metre on November 17 but thereafter it again started increasing and reached 220. For the last week or so it is hovering in the range of 160-190," Beig said.
'Very poor' signifies PM 10 and PM 2.5 levels between 351 and 420, and 211 to 252 micro gram per cubic metre, respectively.
'Severe' is declared when PM 2.5 and PM 10 cross 253, 421 micro gram per cubic metres respectively.
Average readings of PM 2.5 and PM 10, at around 3.30 pm today, were 156.3 and 277.8 micrograms per cubic metre respectively.
Nearly all 10 stations of SAFAR strewn across the city had similar readings. But, significantly, the city has been spared from the "brownish or off-white" smog till now due to atomospheric conditions which has prevented such a development, Beig said.
The air quality is relatively better compared to last year, he said.
"There are two differences with last year. This time the wind movement is not that calm and the temperature is also not very cold, hence the pollutants did not get accumulated. So what we have until now is a milky white fog," he said.
Beig said that apart from PM 2.5, PM 10, carbon monoxide (CO) has gone above the threshold limit at times in the capital.
"Gases such as Ozone, Benzene, Nitrogen dioxide, Sulphur dioxide have stayed well within the safe limits."
Clocking peak levels and the possibility of the situation turning more serious calls for drastic measures, experts from CSE have said.
The Delhi government has proposed that odd and even numbered vehicles will run on alternate days from January 1.