NC Radon Program

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The health risk of excessive exposure to radon gas is an increased risk of lung cancer. Radon gas exposure has been estimated to contribute to between 7,000 and 30,000 lung cancer deaths each year. Smokers are at higher risk of developing Radon-induced lung cancer. The only health effect which has been definitively linked with radon exposure is lung cancer. Lung cancer would usually occur years (5-25) after exposure.

There are no immediate symptoms to indicate exposure. There is no evidence that other respiratory diseases, such as asthma, are caused by radon exposure and there is no evidence that children are at any greater risk of radon induced lung cancer than adults.

There is no debate about radon being a lung carcinogen in humans. All major national and international organizations that have examined the health risks of radon agree that it is a lung carcinogen. The scientific community continues to conduct research to refine our understanding of the precise number of deaths attributable to radon. EPA and the National Cancer Institute (NCI) have independently placed that number at about 15,000 lung cancer deaths each year in the United States.

A few scientists have questioned whether low radon levels, such as those found in residences, increase the risk of lung cancer because some small studies of radon and lung cancer in residences have produced varied results. Some have shown a relationship between radon and lung cancer, some have not. However, the national and international scientific communities are in agreement that all of these residential studies have been too small to provide conclusive information about radon health risks. All major scientific organizations continue to believe that approximately 10% of lung cancers in the United States -- or about 15,000 lung cancer deaths annually -- are attributable to radon.

As long ago as the 16th century, miners were known to suffer from a variety of lung diseases, including lung cancer. It wasn't until the advent of modern medical techniques became available that the actual agent causing the cancer was identified.

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The environmental agent inducing lung cancer was found to be radon gas. The story of this discovery is detailed in Health Risks of Radon and Other Internally Deposited Alpha-Emitters, National Academy Press, 1988. This document is also titled BEIR IV because it was produced by the Biological Effects of Ionizing Radiation Committee.

There were a number of miner's studies described in this book that connected radon exposure to increased risk of lung cancer. A partial listing:

Colorado Plateau Study
Czechoslovakian Uranium Miners
Ontario Uranium Miner's Study
Eldorado Uranium Miner's Study
French Uranium Miner's Study

The ongoing investigation of the health effects of radon produced another National Academy of Sciences report titled The Health Effects of Exposure to Radon.

Radiation can cause damage to the cell through the direct and indirect mechanism of radiation damage.

• In the direct type of damage, the radiation hits the cell nucleus or other important cell structure and can cause cell death or the unrestricted division by the cell known as cancer.

• In the indirect type of damage, the radiation deposits it's energy into the water inside the cell membrane. This energy deposited in the water inside the cell removes electrons from the water atom. Furthermore, chemical species such as the hydroxyl ion (OH) and hydrogen are produced inside the cell. These chemical species are called free radicals, and are very destructive to the cell. Some believe an additional genetic component may be involved, such as when a cell is not killed, but the P53 cancer suppressor gene is damaged. Some believe that this can induce lung cancer.

The risk projection for residents in homes from radon exposure have been reviewed, and adjusted to take into account the difference between radon exposure in mines versus in private homes.

While the studies of miners disclosed the role of radon in lung cancer induction, attention has shifted to finding good studies of residential homes. The most well known study of this type is the one conducted in Iowa by Bill Field and his co-workers. More information can be found on this study

The advantages of this study were that it was an actual case controlled study of a relatively stable population in a high radon area. This study disclosed that the risks of radon are higher than might have been suspected based on earlier studies. Once again, however, the sole health effect from radon is lung cancer. Risk of cancer from radon can be reduced by spending less time in high radon environments, and most of all by reducing the levels of radon in the home.

More about the Health Effects of Exposure to Radon