Research support was provided by the Investigative Fund of The Nation Institute. Follow-ups: “Amplification,” June 19, 2000 and letters exchanges: “Lead–Balloons and Bouquets,” May 15, and “Lead-Letter Office,” July 3, 2000. JAMIE LINCOLN KITMAN The next time you pull the family barge in for a fill-up, check it out: The gas pumps read “Unleaded.” You might reasonably suppose this is because naturally