potential carcinogen in three ways; first being the production of hydroxyl radicals. Ferric ions can be reduced via superoxide and the product can be reoxidized via peroxide to form hydroxyl radicals. Hydroxyl radicals and other reactive oxygen species when generated near DNA can cause point mutations, cross-linkage and breaks. The second being the bolstering of the growth of neoplastic cells by suppressing host defenses. Excessive iron inhibits the activity of CD4 lymphocytes and suppresses the tumoricidal activity of macrophages. The third way it can act as a carcinogen is by functioning as an essential nutrient for unrestricted proliferation of tumor cells. Lithium Lithium is present in biological systems in trace amounts; its functions are uncertain. Lithium salts have proven to be useful as a mood stabilizer and antidepressant in the treatment of mental illness such as bipolar disorder. Biometals in medicine Metal ions and metallic compounds are often used in medical treatments and diagnoses. Compounds containing metal ions can be used as medicine, such as lithium compounds and auranofin. Metal compounds and ions can also produce harmful effects on the body due to the toxicity of several types of metals. For example, arsenic works as a potent poison due to its effects as an enzyme inhibitor, disrupting ATP production. References Biology and pharmacology of chemical elements