Why does Alfa often feel uncomfortable at work in the novel, Walking to the Bus-Rider Blues?

Alfa is often uncomfortable at work, fearing that he will accidentally slice open bags of flour when he cuts open boxes. His fear leads to nightmares, in which, he does slice open the flour and Mr. Greendale shouts, "Look, Alfred's white now!" He is also stressed by Mr. Greendale's antagonistic attitude toward him, making racist remarks and unfair comments about Alfa's work performance.