Lung Cancer Home > Radon and Cancer
Scientists have found a link between radon and cancer. Long-term exposure to high levels of radon (a radioactive gas) may cause lung cancer. Radon decays quickly, giving off tiny radioactive particles; when inhaled, these particles can damage the cells that line the lung, leading to lung cancer. The relationship between radon and cancer was first noticed in studies of uranium miners and was confirmed with experimental animal studies. While cigarette smoking causes the vast majority of lung cancer cases, an estimated 15,000 to 22,000 lung cancer deaths per year are related to radon.
Radon is a radioactive gas released from the normal decay of uranium in rocks and soil. It is an invisible, odorless, tasteless gas that seeps up through the ground and diffuses into the air.
Radon decays quickly, giving off tiny radioactive particles. When inhaled, these radioactive particles can damage the cells that line the lung. Long-term exposure to high levels of radon can lead to lung cancer, the only cancer proven to be associated with inhaling radon.
Cigarette smoking is the most common cause of lung cancer. Radon represents a far smaller risk for this disease, but it is the second leading cause of lung cancer in the United States. Scientists estimate that approximately 15,000 to 22,000 lung cancer deaths per year are related to radon.
Although the association between radon exposure and smoking is not well understood, exposure to the combination of radon gas and cigarette smoke creates a greater risk for lung cancer than either factor alone. The majority of radon-related cancer deaths occur among smokers.
Radon was identified as a health problem when scientists noted that underground uranium miners who were exposed to it died of lung cancer at high rates. Results of miner studies have been confirmed by experimental animal studies, which show higher rates of lung tumors among rodents exposed to high radon levels.
Scientists agree that radon causes lung cancer in humans. Recent research has focused on specifying the effect of residential radon on lung cancer risk. In these studies, scientists measure radon levels in the homes of people who have lung cancer and compare them to the levels of radon in the homes of people who have not developed lung cancer.
One of these studies examined residential radon exposure in Iowa among females who had lived in their current home for at least 20 years. This study included 413 females with lung cancer and 614 females without lung cancer. During the study, radon levels were tested in homes, lung cancer tissues were examined, and the scientists collected information about home characteristics and other topics. Results from this study suggested a link between exposure to radon and lung cancer.
Scientists have conducted more studies like this in other regions of the United States and around the world. Many of these studies have demonstrated an association between residential exposure to radon and lung cancer, but this finding has not been observed in all studies. The inconsistencies between studies are due in part to the small size of some studies, the varying levels of radon in many homes, and the difficulty of measuring a person's exposure to radon over time.
Researchers have combined and analyzed data from all radon studies conducted in Canada and the United States. By combining the data from these studies, scientists were able to analyze data from thousands of people. The results of this analysis demonstrated a slightly increased risk of lung cancer associated with exposure to household radon. This increased risk was consistent with the level of risk estimated based on studies of underground miners.
Researchers are also investigating more precise ways to measure a person's exposure to radon over time. In a study published in 2002, scientists examined radon exposure among people in Sweden who had not smoked daily for more than a year. This study included 110 people with lung cancer and 231 people without lung cancer. As with previous studies, the scientists measured radon levels of indoor air. The researchers also used a new technique of analyzing glass to estimate radon exposure over time. Using this technique, the scientists took measurements from glass in an object (for example, a mirror or picture frame) that was at least 15 years old and had been in the person's home throughout that time, even if the person had moved from one home to another. In this study, both of the techniques for measuring radon demonstrated a relationship between long-term exposure to radon and lung cancer, and supported the results of previous studies.