7 countries meet WHO's air quality guidelines; global air quality remains a major health risk.

7 countries meet WHO's air quality guidelines; global air quality remains a major health risk. Despite U.S. progress, air pollution contributes to several serious health issues domestically and worldwide. A new report highlights the worsening global air quality, which endangers human health. Glory Dolphin Hammes, CEO of IQAir North America, discusses this issue with William Brangham.