Tetraethyllead was introduced into gasoline in 1922, and lasted about 70 years. The effect would have been greater after WW2 due to there were more cars and a l

Tetraethyllead was introduced into gasoline in 1922, and lasted about 70 years. The effect would have been greater after WW2 due to there were more cars and a larger population with greater desire for mobility and closer proximity to cars. During the Depression there were fewer cars for economic reasons, and during WW2 fewer for reasons of rationing and recycling, raw material went to the war effort.