New Delhi, May 18 (IANS): As the country stepped into the fourth phase of the lockdown, the national capital, which for two months saw azure blue skies and breathable air, witnessed a sudden spike in the air pollution on Monday.

The level of Particulate Matter (PM) with diameters of 2.5 and 10 microns, which are too small to be filtered out of the body, stood at 83 and 183 micrograms per cubic metre, respectively.

SAFAR categorises air quality in the 0-50 range as good, 51-100 as satisfactory, 101-200 as moderate, 201-300 as poor, 301-400 as very poor and above 400 as severe.

Data by the Central Pollution Control Board showed that overall air quality near Punjabi Bagh area stood at 298 micrograms per cubic metre, followed by Delhi Technological University, Bawana and Mundka.

Out of 36 stations, the AQI in as many as 16 stations, was above 200 micrograms per cubic metre till 4 p.m. on Monday.

According to the System of Air Quality Weather Forecasting and Research, "this is owing to the dust transport from the Rajasthan region which is going to keep PM 10 levels high until evening of May 18 and then start to descend."

The weather forecasting agency further said that the dust is likely to be a dominant factor in contributing to particulate pollution for the coming days. Researchers indicated that PM 10 and PM 2.5 will be 215 and 103 micrograms per cubic metre on Tuesday.

According to a study conducted by the Indian Institute of Technology (IIT) Delhi, in the earlier stage of the lockdown, the country had witnessed 43 and 31 percent decreases in PM 2.5 and PM 10 as compared to previous years. But, in the past few days it appears to be increasing again.

If the low levels of air pollution reached during the lockdown period are maintained, India's annual death toll could reduce by 6.5 lakh, the study had stated.