Radon FAQs - Definition and Debate

by DoItYourself Staff

Definition and Debate - Studies - Types of Risks

Definition:

Radon is a gaseous radioactive element having the symbol Rn, the atomic number 86, an atomic weight of 222, a melting point of -71ºC, a boiling point of -62ºC, and 18 radioactive isotopes; it is an extremely toxic, colorless gas; it can be condensed to a transparent liquid and to an opaque, glowing solid; it is derived from the radioactive decay of radium and is used in cancer treatment, as a tracer in leak detection, and in radiography. (From the word radium, the substance from which it is derived.).

What's the Debate on Radon?

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.

How Do We Know Radon is a Carcinogen?

The World Health Organization (WHO) and the US Department of Health and Human Services, as well as EPA, have classified radon as a "Class A" known human carcinogen, because of the wealth of biological and epidemiological evidence and data showing the connection between exposure to radon and lung cancer in humans.

The World Health Organization, the National Academy of Sciences and other scientific organizations agree that studies of the miners are the best scientific information for estimating radon health risks in homes. The Lubin/Boice meta-analysis paper also concludes that the miners studies are the best data source for analyzing residential radon risk. Based on the miner data, NCI has previously estimated that 15,000 people die of lung cancer from residential radon each year in the U.S.

There have been many studies conducted by many different organizations in many nations around the world to examine the relationship of radon exposure and human lung cancer. The largest and most recent of these was an international study, led by the National Cancer Institute (NCI), which examined the data on 68,000 underground miners who were exposed to a wide range of radon levels. The studies of miners are very useful because the subjects are humans, not rats, as in many cancer research studies. These miners are dying of lung cancer at 5 times the rate expected for the general population. Over many years scientists around the world have conducted exhaustive research to verify the cause-effect relationship between radon exposure and the observed increased lung cancer deaths in these miners and to eliminate other possible causes.

In addition, there is an overlap between radon exposures received by miners who got lung cancer and the exposures people would receive over their lifetime in a home at EPA's action level of 4 pCi/L, i.e., there are no large extrapolations involved in estimating radon risks in homes.