Bismuth nitrate is a salt. It contains the heavy metal bismuth. People use bismuth nitrate for preventing kidney damage caused by cancer drugs, for preventing bone marrow damage caused by radiation, and for a digestive tract infection that can lead to ulcers (Helicobacter pylori or H.
Elemental bismuth is nontoxic, but bismuth salts can cause toxicity. Bismuth salts are relatively insoluble, so environmental and occupational exposure is low. Most toxic exposure to bismuth is from consumption, usually from medicinal use.