Briefly describe Stanislovas' job. In what way does Sinclair use it as a vehicle to continue his muckraking?

Teta Elzbieta goes to a priest and gets a fraudulent document saying that Stanislovas is sixteen, older than he actually is, and he takes a position working with a machine that packs lard into cans. He earns three dollars a week for his work. Spraying lard into cans is a disgusting job. For poor Stanislovas, this will be his life's fate. He will work in a dark room with the stink and mess of lard. He will not go back to school.