Table 1 Air quality assessment—variations and change (%) of average concentrations for different air pollutants during the pre and COVID-19 pandemic confinement, 2020 among populous sites of four major metropolitan cities in India
Pollutants Pre-lockdown values Lockdown Variation and % change (pre-lockdown and lockdown)
Site 1 Site 2 Site 3 Site 4 Site 1 Site 2 Site 3 Site 4 Site 1 Site 2 Site 3 Site 4
AQI 238 151 144 68 134 62 59 64 − 104 (44%) − 89 (59%) − 86 (59%) − 4 (6%)
PM2.5 238 132 135 56 122 36 36 26 − 116 (49%) − 96 (73%) − 99 (73%) − 30 (54%)
PM10 150 116 122 60 100 61 45 49 − 50 (33%) − 54 (47%) − 77 (63%) − 10 (17%)
NO2 44 48 55 9 31 7 11 10 − 13 (29%) − 41 (86%) − 43 (79%) 1 (7%)
NH3 10 2 8 14 4 1 2 9 − 6 (63%) − 1 (58%) − 6 (74%) − 4 (30%)
SO2 19 12 11 14 14 5 9 9 − 4 (24%) − 7 (58%) − 2 (15%) − 6 (39%)
CO 53 28 33 25 84 13 22 35 31 (59%) − 15 (55%) − 11 (32%) 9 (37%)
O3 35 85 29 36 73 34 51 65 38 (109%) − 51 (60%) 22 (77%) 29 (80%)
PM2.5 in μg/m3, PM10 in μg/m3, CO in μg/m3, NH3 in μg/m3, NO2 in μg/m3, SO2 in μg/m3, and O3 in μg/m3
AOI air quality index