Current water-filtering technology is costly, but MIT scientists are testing a simpler and cheaper method that uses wood from white pine trees. Wikimedia Commons hide caption

itoggle caption Wikimedia Commons

Dr. Jim Olson meets with Carver Faull at Seattle Children's Hospital in August. Carver, now 12, had surgery to remove a brain tumor in 2012. Matthew Ryan Williams for NPR hide caption

itoggle caption Matthew Ryan Williams for NPR