Fig. 3.
Comparison between air pollutants in the first four months of 2020 with daily historical mean between 2015 and 2020. Black lines indicate beginning of lockdown in each location
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.