**1.8 Radium**

The heavy metal radium has had a long association with negative effects on human health. The harmful fact associated with radium is its radioactivity. Radium releases ionizing radiation through the decaying of radium into a toxic gas [91]. Radon contamination in the form of ionizing radiation can be associated through environmental and occupational exposure. Occupational exposure to radium is often associated with coal mining [92]. Coal mining exposure also implies radium contamination of any water or liquid residue used in the mining process [93]. The occupational exposure of radium can be associated with exposure through contact with building materials, soil and water systems. An Italian study demonstrated radium can accumulate when associated with confined space, such as in buildings, basements and other storage facilities [91]. Another overlooked substance that can contribute to the increased presence and concentration of radium in confined spaces is cigarette smoke [93]. This observation clearly implicates smoking and radium exposure that collectively could synergistically impact human health [93].

The development of several types of cancer have linked to radium, thus labeling it as a known carcinogen. Because the main occupational exposure of radium comes from occupations where inhalation is the primary method of exposure, the predominate form of cancer is lung cancer [91]. As a significant agent responsible for inducing cancer following radium exposure is the release of the ionizing radiation. With that said, when under controlled conditions, radium is used in the clinical treatment for human ankylosing spondylitis [94]. However, careful administration is critical because injection of radium has been associated with the development of several types of leukemia [94]. In animals, radium injections were demonstrated to induce the formation of osteosarcomas [94]. In a clinical case report, a patient being treated with radium-223 developed a cutaneous squamous cell carcinoma indicating such patients need to be followed clinically by a dermatologist [95].
