An important aspect of Ground Zero is the focus on each character’s day-to-day struggle for sheer survival, an uphill battle against the monstrous denizens of the wasteland, the haunting savages hiding in the ruins of old cities, and a fight against the lethal nature of the world itself. A landscape pitted with radiated craters, poisoned wells and water systems, starved of shelter and places of safety, the wasteland itself is as much a hazard to life as any of its most formidable inhabitants. These rules deal with the major dangers characters are likely to face during the course of play.
You will note that many of the environmental agents listed above include a rating for something called "Creep":