Occupational medicine is the branch of clinical medicine most active in the field of occupational health. OM specialists work to ensure that the highest standards of occupational health and safety can be achieved and maintained. While it may involve a wide number of disciplines, it centers on the preventive medicine and management of illness, injury or disability that is related to the workplace. Occupational physicians must have a wide knowledge of clinical medicine and be competent in a number of important areas. They often advise international bodies, governmental and state agencies, organizations and trade unions. There are contextual links to insurance medicine.