Copper is a metallic element (Atomic Number 29) that in the human body is required in trace amounts, primarily in the construction of enzymes. It is found in the liver, muscles and bones. It is found in many foods including shellfish (where copper takes the place of iron in the blood), nuts, olives and avocados. In a person with a normal metabolism, excess copper is filtered by the liver and excreted through the bile duct.
However, too much copper is toxic as it created oxides which damage body tissues and DNA. Deaths are rare unless a person deliberately swallows copper salts. Environmental exposure (such as the use of copper cookware or copper compounds in drinking water) can usually be dealt with by the body. However, there are genetic disorders (particularly Wilson's disease) that cause copper to accumulate in the body.