Air pollution results in the premature death of 7 million people around the world each year. It is a major global killer harming people in nearly every corner of the globe.  My guest today, Beth Gardiner is a journalist who traveled the world examining the impact of air pollution. Her new book is called Choked: Life and Breath in the Age of Air Pollution.    In our conversation she shares stories from her reporting, which includes not only detailing the harmful impact of air pollution but also an examination of policies that are working toward cleaner air for all.