What is the difference between a hygiene and a safety hazard?

There is a deal of overlap between hygiene and safety in general and therefore between hygiene and safety hazards.

Broadly, a safety hazard is one for which the result is promptly noticeable and readily identifiable as to the proximate cause. For example, falling off a ladder, and the resulting injuries, are readily seen to be connected.

With a hygiene hazard, the exposure to the hazard and the resulting injury may be separated in time and the cause and effect may not be as readily apparent. For example, exposure to benzene vapor can result in liver cancer, but it takes a study of many people over a long time to clearly demonstrate that.