Radon History

Radon was discovered by Friedrich Ernst Dorn, a German chemist, in 1900 while studying radium’s decay chain. Originally named niton after the Latin word for shining, “nitens,” it has been known as radon since 1923.

Since radium was expensive and in great demand for the treatment of cancer, radon gas, which is a natural decay product of radium, also was thought to have similar curative powers.  So radon was sort of a “poor man’s radium”.

In the United States, epidemiological studies showed there was an unusual incidence of lung cancer among uranium miners.  Eventually, occupational limits were established for radon concentrations in uranium mines.

Elevated levels of radon in homes were not recognized as a potential public health threat until the mid-1980’s.  Mr. Stanley Watras, a worker at the Limerick Nuclear Power Plant located in eastern Pennsylvania, set off a radiation detector upon entering the nuclear power plant.  At the time the nuclear power plant was under construction and had not received its nuclear fuel. The utility discovered extremely elevated levels of radon in his new home.  The Commonwealth of Pennsylvania began testing homes for radon and found elevated levels of radon in them as well. Elevated levels of radon were associated with a geological structure called the Redding Prong.  In Virginia there is a similar structure called the Triassic Basin.

The US Environmental Protection Agency (EPA) was enlisted to provide additional assistance and other states were encourage to study the indoor radon issue in their respective state.

In 1986, VDH conducted a state-wide survey of 800 homes and found that approximately 12% of the homes that were screened for radon had elevated levels of radon above 4 picocuries/liter, EPA’s recommended action level.  In 1992 the EPA supported a larger study of approximately 1,600 homes.  The results of this study verified the results of the earlier study.  The results also indicated that radon levels generally were not elevated in Tidewater Virginia, which is east of the fall line of Virginia’s rivers (East of Interstate 90).

During the late 1980’s the EPA established an extensive Indoor Radon Program which provided funding to the states through State Indoor Radon Grants.  This program made publications available for the states to distribute important information about radon to the public, established regional training centers for radon professionals and a radon proficiency program for radon testers.  However, the EPA proficiency program was abolished in 1998. Certification of radon professionals is currently conducted by either the National Radon Safety Board (NRSB) or the National Radon Proficiency Program (NRPP) of the American Association of Radiation Safety Technicians (AARST).

While the EPA has no regulatory authority regarding indoor radon levels in air, the organization has statutory authority for carcinogens in water.  Since radon is a known carcinogen, the EPA is required to establish maximum concentration levels (MCLs).  Congress amended the Safe Drinking Water Act to require the EPA to solicit the National Academy of Science to evaluate the risk of cancer, and validate the transfer coefficient of radon in water to air.  Congress also set a date of October 2002 to publish a final rule for a drinking water standard for radon in water.  The EPA published a proposed rule where the proposed MCL was 300 pCi/l in water.  Congress also allowed EPA to suggest an alternate MCL if the States participated in a “Multi-media Mitigation” Program to reduce radon levels in air, since inhalation is the major exposure pathway.  The proposed alternate MCL is 4,000 pCi/l in water.


Office of Radiological Health | 109 Governor Street, 7th Floor | Richmond, VA 23219

Telephone (804) 864-8150 | Fax: (804) 864-8155