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. 2020 Nov 21;756:144009. doi: 10.1016/j.scitotenv.2020.144009

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© 2020 Elsevier B.V. All rights reserved.

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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Fig. 5 — Comparison of NO₂ (a and b), SO₂ (c and d), PM_2.5 (e and f), CO (g and h), and O₃ (i and j) between C-19 lockdown and BAU settings over selected cities in the study area. Statistical analysis was performed using R 4.0.2 (R Core Team, 2019).