Average levels of various pollutants, including PM10, PM2.5 and nitrogen dioxide, in Delhi last year were the lowest since 2014, according to the Delhi Economic Survey report. Government data also showed that average levels of the major pollutants in the city have been decreasing steadily over the years. The annual average concentrations of PM2.5, fine particulate matter that is about three per cent the diameter of a human hair and can lead to premature deaths from heart and lung diseases, decreased from 149 microgram per cubic meter (g/m3) in 2014 to 101 g/m3 in 2020, it said.