Barium What Is Barium? Barium is a naturally occurring element that belongs to the group of heavy metals . While it has useful applications in medicine and industry, certain forms of barium can be toxic to humans when exposure levels become elevated. Water-soluble and acid-soluble forms of barium are considered particularly hazardous because they can be absorbed by the body more easily. Excessive exposure has been linked to a variety of health concerns, including cardiovascul