What are the health effects of radon exposure?
The Surgeon General has warned that radon is the leading cause of lung cancer in the United States after cigarette smoking. There are currently no conclusive data on whether children are at greater risk than adults from radon. However, a reading of 4.0 pCi/L is considered to be the equivalent of smoking a half-pack of cigarettes a day. Since children are typically non-smokers, we might assume a greater risk over time.
Only cigarette smoking is responsible for causing more lung cancers. If you smoke and you are exposed to elevated radon levels, your risk of lung cancer is especially high. The U.S. Environmental Protection Agency provides radon risk comparison charts for people who smoke and those who have never smoked. Stop smoking and lower your radon level to substantially reduce your risk of developing lung cancer.
What is the mechanism? Radon gas decays into radioactive particles that attach to tiny dust particles in the air and the surroundings.. When inhaled, these particles attach to the lung wall. As the radon particles decay, they release small bursts of energy (Alpha particles in particular) that can damage the lung cells DNA. When the cells repair themselves using copies of the damaged DNA there may be small changes (mutations) which can develop into cancerous cells. These cells can multipy resulting in lung cancer. Not everyone exposed to elevated levels of radon will develop lung cancer, and the amount of time between exposure and the onset of the disease may be many years. However, there are many documented cases of children and young adults raised in high-radon homes developing lung cancer. Some survived, many did not. Radon is considered a silent killer. Breathing radon does not appear to cause any short-term health effects such as shortness of breath, coughing, headaches, or fever - which might otherwise serve as an early warning.
In 1998, the National Academy of Sciences (NAS) released the Biological Effects of Ionizing Radiation (BEIR VI) Report, "The Health Effects of Exposure to Indoor Radon." The study reviewed and evaluated data from many prior studies and drew conclusions. It fully supports estimates by the EPA that radon causes about 21,000 lung cancer deaths per year. While some people debate the number of deaths, it is widely agreed that radon is a Class A carcinogen.
Radon can come from the water as well as from the air. Research suggests that swallowing water with high radon levels may pose risks, too, although risks from drinking water containing radon are much lower than those from breathing air containing radon.
A NAS report on radon in drinking water, "Risk Assessment of Radon in Drinking Water," was released in 1999. It concluded drinking radon in water causes about 19 stomach cancer deaths per year.
The EPA provides more information about health effects from radon in their publication, Radon—A Physician's Guide.