Two 5,000-gallon tanks store fluorosilicic acid on Friday, May 10, 2013 at the Geren Island Water Treatment Facility in Stayton, Ore. The chemical is used to add fluoride to the city of Salem’s water. The city has fluoridated since 1964 but has used fluorosilicic acid only since 2001. (Photo: Gino Corridori/KATU News)
