Lead in petrol is a story all in itself. Tetraethyl lead was found to reduce "knocking" (preignition) in petrol/gasoline engines.
The discovery was made by a walking disaster named Thomas Midgely Jr. (He also "invented" Chlorofluorocarbons - the aerosol component that wrecked the ozone layer.)
T.E.L. Was known to release lead into the atmosphere and cause progressive (and irreversible) damage to the nervous system of higher animals. This uncomfortable fact was hidden by the auto manufacturers, the oil companies and the manufacturers of the stuff for years.
Most countries have now banned the use of T.E.L. In gasoline. It lingers on in the third world, and a few Arab countries.
For the record Thomas Midgely Jr. Died at his own hand, when a contraption of his own design, invented to lift him out of bed, collapsed and strangled him.
