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Toxicologic Effects of Radon Exposure

Posted June 2, 2008

John J. Nelson, MD, MPH
CAP Toxicology Resource Committee

Radon exposure is an entity that falls within the realm of environmental toxicology. While other elements such as lead have taken the forefront in clinical screening, the issue of radon exposure is important for primary care physicians to bear in mind during the practice of medicine. Radon (Rn, atomic number 86) is a radioactive noble gas and is a natural decay product of uranium, actinium, and thorium. Radon is the heaviest noble gas and was discovered by Friedrich Ernst Dorn in 1900 at which time it was initially named radium emanation, then niton, and finally radon in 1923. Radon emits α and γ particles; and apart from being a risk to miners and others who work underground, radon can enter buildings through the building materials themselves or through microscopic cracks in a building structure causing exposure risk to inhabitants.1 Geographic areas of the United Sates (US) that have known high levels of radon include areas of New York, New Jersey, and Pennsylvania, yet radon may be in soil formations throughout the US.

The concern for identifying radon exposure lies in the increased risk of developing bronchogenic carcinoma of the lung. The average concentration of radon in outdoor air is 0.4 picocuries per Liter (pCi/L).2 The Environmental Protection Agency estimates that over eight million homes have radon levels greater than 4 pCi/L.3 The radon particles are inhaled and the resulting radioactive decay products and the subsequent exposures lead to dysplasia and possibly carcinoma. Risk of carcinoma development is compounded by cigarette smoking, not only from the carcinogens in cigarette smoke itself, but also in radon binding to the particulate matter in cigarette smoke.

Estimates of deaths from indoor radon exposure are in the thousands4 and a pooled analysis of European studies of indoor radon exposure resulted in a relative risk (RR) of 1.08%.5 A highly studied population group concerning radon exposure is underground miners. Several studies among uranium miners6 and iron ore miners7 have linked inhalation of radon particles with lung carcinoma. It has been noted that indoor radon exposures are much lower than underground mining exposures, yet the duration of exposure and large numbers of individuals exposed highlights the importance of indoor radon’s contributions to carcinogenesis.8 One study in the United Kingdom (UK) concluded that radon was responsible for 6.5% of all deaths from lung cancer in the UK, including 5.5% from the joint affect of smoking and radon and 1% to radon alone.9 Other reports indicate indoor radon may be responsible for up to 4.5% of lung carcinomas.10 Numerous case studies of radon exposure performed over the past few decades have added to the scientific and clinical evidence that supports radon’s role in lung carcinogenesis.

The goal of the physician and perhaps public health advocates is to make patients aware of the risks of radon, especially in high-risk geographical areas. Screening can be done by a number of methods;11 some of the more common methods use charcoal canister devices that can be acquired through some hardware stores and state health departments, which are then analyzed by a central laboratory. Indoor radon levels can be lowered by increasing ventilation, sealing foundations, and installing air-cleaning devices.3 Awareness of risk and assessment of possible radon exposure are the goals that physicians and public health officers can promote in preventing radon-related morbidities.

References

  1. Goldfrank LR, ed. Goldfrank&38217;s Toxicologic Emergencies. 2nd ed. New York, NY: McGraw-Hill; 2002:1522.
  2. US Environmental Protection Agency. Health risks. http://www.epa.gov/iaq/radon/healthrisks.html. Updated March 10, 2008. Accessed April 21, 2008.
  3. Little DN. Children and environmental toxins. Primary Care. March 1995; 22(1):72–73.
  4. Butland BK, Muirehead CR, Draper GJ. Radon and leukaemia [letter]. Lancet 1990; 335:1338-1339.
  5. Boffetta P. Human cancer from environmental pollutants: the epidemiologic evidence. Mutat Res. 2006;608:157–162.
  6. Samet JM, Kutvirt DM, Waxweiler RJ, et al. Uranium mining and lung cancer in Navajo men. N Engl J Med. 1984; 310:1481–1484.
  7. Radford EP, Renard KG. Lung cancer in Swedish iron miners exposed to low doses of radon daughters. N Engl J Med. 1984; 310:1485–1494.
  8. Boffetta P Nyberg F. Contribution of environmental factors to cancer risk. British Medical Bulletin. 2003;68:71–94.
  9. Darby S. et al. Radon: a likely carcinogen at all exposures. Ann Oncol. 2001;12:1341–51.
  10. United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effects of ionizing radiation. UNSCEAR 2000 Report to the General Assembly, with Scientific Annexes. Vol I: Sources. New York, NY: United Nations; 2000.
  11. US Environmental Protection Agency. Radon measurement method definitions. http://www.epa.gov/iaq/radon/methods.html. Updated October 29, 2007. Accessed April 21, 2008.

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NewsPath® Editor: C. Leilani Valdes, MD
This newsletter is produced in cooperation with the College of American Pathologists Public Affairs Committee and the NewsPath Editorial Board and may be reproduced in whole or in part as a service to the medical community. Copyright © 2008 by the College of American Pathologists.
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