This is part four of Undark and the Pulitzer Center's global series on PM2.5 (https://undark.org/breathtaking https://undark.org/breathtaking), a deadly form of

This is part four of Undark and the Pulitzer Center's global series on PM2.5 (https://undark.org/breathtaking https://undark.org/breathtaking), a deadly form of air pollution that claims more than 4 million lives each year. The investigation is accompanied by photos by Pulitzer Prize-winning photographer Larry Price.