What is the theme of the chapter Lead?

Primo Levi's complex probing of the Holocaust, including his survival of Auschwitz and pre- and post-war life, is organized around individual elements. Some parts are factual memoir, others are fiction, and some read like fairy tales or ancient fales.
Two such fables, written while he worked as a chemist before joining the resistance, are paired according to the elements' radically different properties, also metaphorically present in people. These are lead, which is stable and represents stolidly persisting, and mercury, which is volatile and linked to instability and rapid change.
Levi incorporates the qualities of the element into the tone of the story and makes the character's personality compatible with those qualities as well.
"Lead" centers on a lead artisan, or smith, apparently in ancient times. His itinerant progress to find work takes him to many places and stimulates him to try different jobs and crafts. But lead is what he understands and excels at. Another quality of lead is that it is toxic. Continued exposure poisons the person who touches or ingests it. By not changing his craft, the leadsmith is signing his own death certificate. However, he is returning to his emotional home as well, to his pregnant wife, in time to meet their new baby before he passes away—a child who seems destined to follow his path.