ST. LOUIS â The Gateway Arch gradually is losing some of its silver sheen, as a variety of forces â from salt to body oils to graffiti â take a toll on the stainless steel monument to westward expansion and a symbol of St. Louis. Now, a group of national nonprofit organizations and preservationists are suggesting ways the National Park Service could begin to clean the Arch's shiny skin. "This is fantastic information to have," said Pam Sanfilippo, a program manager of museum services for Gateway Arch National Park. "Planning for future needs for the park, this will definitely be front and center in our minds."