I'm not an expert, but I would suspect that life in North Korea is good training for being very careful with things like this.
As Mrs. Song would observe a decade later, when she thought back on all the people she knew who died during those years in Chongjin, it was the “simple and kindhearted people who did what they were told—they were the first to die.”
-- Nothing to Envy: Ordinary Lives in North Korea by Barbara Demick