Tennessean: Matt Landon pulls a respirator over his longish hair, snugging the facepiece down over his nose and mouth. He’s riding shotgun in a car on Intestate 40 headed east, 10 miles out from Harriman, Tenn., where millions of cubic yards of Tennessee Valley Authority coal ash lie in fields, yards and the Emory River. Landon explains that he wears a respirator whenever he gets this close. “The thing about fine particulates is, you don’t know it’s there,” he said, his voice …