As many as 9 out of 10 people breathe polluted air, the United Nations Secretary-General António Guterres wrote on Twitter.
"As many as 9 out of 10 people breathe polluted air, leading to some 7 million premature deaths each year. This number could double by 2050 if we don't act decisively now. Let's work together to clean the air that we breathe so we may protect people & planet," he wrote.