New Delhi, Jul 13 (IANS): The air quality of the national capital improved drastically on Monday, with the particulate matter with a diameter of 2.5 and 10 microns, which are too small to be filtered out of the body, mounting to 49 and 22 micrograms per cubic.

The System of Air Quality Weather Forecasting and Research categorizes 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.

"A marginal deterioration in air quality is expected. The AQI is likely to stay in satisfactory to the moderate category for the next two days," the Centre-run System of Air Quality Weather Forecasting and Research predicted.

As per the forecast, PM10 pollutants are expected to increase to 56 on Tuesday, which falls in the 'satisfactory' category while PM2.5 pollutants are expected to rise up to 26, which falls under the 'good' category.

The capital city had witnessed the cleanest air quality of the year with the overall AQI at 42, under the 'good' category, in March when the nation-wide lockdown was imposed.

According to a study conducted by the Indian Institute of Technology (IIT) Delhi, 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.