Residents of Jackson, Mississippi; Flint, Michigan; and parts of New York City, Baltimore and the state of Hawaii have all dealt with contaminated water supply over the years. Why are so many cities having problems with their drinking water? Shannon Marquez, dean of global engagement and professor of water, sanitation and hygiene at Columbia University, joins John Yang to discuss. Stream your PBS favorites with the PBS app: https://to.pbs.org/2Jb8twG Find more from PBS NewsHour at https://www.pbs.org/newshour Subscribe to our YouTube channel: https://bit.ly/2HfsCD6 Follow us: Facebook: http://www.pbs.org/newshour Twitter: http://www.twitter.com/newshour Instagram: http://www.instagram.com/newshour Subscribe: PBS NewsHour podcasts: https://www.pbs.org/newshour/podcasts Newsletters: https://www.pbs.org/newshour/subscribe