"These early toothpaste tubes were made of tin and lead, and remained basically the same until a metal shortage during World War II led to mixed plastic and metal tubes. By the 1950s, manufacturers were making plastic tubes for suntan lotion, but this type of polyethylene tube reacted with toothpaste ingredients."
You brushed your teeth, then chewed on the tube to save you going to the dentist for fillings.
Good old lead. Get it doon ye.