Fig. 4 The concentration of air pollutants (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) during pre-lockdown and lockdown period at 17:00 IST among four different air quality monitoring stations of the CPCB for four major metropolitan cities in India (site 1—ITO, Delhi, site 2—Worli, Mumbai, site 3—Jadavpur, Kolkata, and site 4—Manali Village, Chennai)