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.
Annual population-weighted average PM2.5 (a) and 90% quantile of population-weighted maximum daily 8-h average O3 (b) pollution in China and key regions from 2015 to 2020. Data sources: Tracking Air Pollution in China database, http://tapdata.org.cn/(Geng et al., 2021 [33]; Xiao et al., 2021a [34]).
