For decades, leaded gas was billed as something that would improve engine performance. When the health risks of lead exposure became widely accepted, it was phased out in the United States. The United Nations has announced that leaded gas in passenger vehicles has now been phased out around the world. A stockpile in Algeria was used up in July. Marco Werman speaks to the person behind the nearly 20-year effort to get rid of leaded gas in passenger vehicles: Rob de Jong, head of the sustainability unit at the United Nations environment program, based in Nairobi.