Oct 02, 2019, 10:53AM IST

Source: TOI.in

The national capital this year witnessed cleanest air in 9 years. While the average PM10 level was 99 microgram per cubic metre (as against a safe standard of 100), average PM2.5 level was recorded at just 40 microgram per cubic metre, well below the safe limit of 60. In September 2015, the average PM10 concentration was 239 microgram per cubic metre, while the average PM2.5 level was 72 microgram. Compared to then, PM10 concentrations have declined by 58% and PM2.5 has come down by 44%. The average AQI was 194 in September 2015, 162 in 2016, 139 in 2017 and 112 in 2018.