Is there a difference between occupational hygiene risks and occupational medicine risks?

Yes, there is a a difference between occupational hygiene risks and occupational medicine risks, although there is also substantial overlap.

Occupational hygiene risks are risks in the work environment that might impact the health of a person in that environment.

Occupational medicine risks include many of those, but also include medical or physical conditions that a person might have that could pose a risk to the health of that person if he or she were to spend time in a particular occupational setting.