Lead in gasoline lubricated the upper cylinder, and had zero environmental effect.
The occurrence of every known disease condition was measurably lower when lead was in the gas. (not that I attempt to claim direct causation)
The removal of sulfur has been destructive in every way to engines. Removing the catalytic converters would have been a far better choice.
Environmentalism is killing everything.
.
Lead lubbed the valve seats. There is no positive benefit to spreading all around. Most can get their MDR from leaded solder fumes while using their soldering station or left over pipe joints. Burnt Sulphur stinks.