exposure.4 But the prognosis of lung cancers associated with residential radon exposure has not been extensively studied
EMERGING ISSUES BRIEF Together-Eliminating Cancer
Radon gas can seep into a house through the basement and foundation.
Radon and Cancer
By Angeline S. Andrew PhD, Assistant Professor, Norris Cotton Cancer Center
Radon gas is the second leading cause of lung cancer after tobacco smoke worldwide.1 In the United States approximately 18,600 lung cancer deaths per year are attributed to residential radon exposure, and lung cancer risk is 29 percent higher for people exposed to high levels of radon gas in their homes compared to those with low exposure.2
One in three NH homes may have elevated levels of radon
The New Hampshire Department of Environmental Services estimates that one in three New Hampshire homes has elevated levels of radon.3 Based on the local geology, soil characteristics, and radon Potential for elevated indoor radon measurements, the Environmental Protection Agency considers all http://www.epa.gov/radon/ counties in New Hampshire to have moderate to high potential for elevated indoor radon levels (see map).
Why is residential radon exposure harmful?
The main source of radon exposure is contaminated indoor air. As a radioactive mineral called uranium-238 decays in the rocks and soil underneath a house, a colorless, odorless gas—radon—is released as a natural byproduct. This radon gas can seep into the house through the basement and foundation and attach to dust particles in the air. When inhaled, these particles generate radiation that damages deoxyribonucleic acid (DNA) and other components of cells in the lung.5 This damage can lead the lung cells to proliferate uncontrollably, forming a tumor.
Studies of underground miners in the 1950s established the relationship between radon and lung cancer, indicating that radon exposure confers the greatest risk of lung cancer in the period 5 to 15 years after exposure.4 But the prognosis of lung cancers associated with residential radon exposure has not been extensively studied, and ongoing studies have not identified molecular features unique to radon-related tumors that can be used to guide cancer treatment.5 Radon exposure is associated with lung cancer among nonsmokers and is estimated to cause 30 percent of the lung cancer deaths among those nonsmokers who are not exposed to other lung carcinogens in the workplace.6,7 Certain people may have inherited genetic factors that make them particularly susceptible to radon-related lung cancers.8 Smokers are also more susceptible to radon gas-related lung cancer, since the damage caused by tobacco smoke may synergize with the effects of radon.9 Smoking in the home creates more particulates in the air for radon to bind to, potentially increasing exposure and risk for all inhabitants, including children. The radon-induced lung cancer risk is 25 times higher for smokers than for nonsmokers10 (smoking prevention and cessation remain the most important way to avoid lung cancer).11 While radon gas can also be found in the water source supplying a home, this is usually a minor source of risk compared to radon exposure from soil. Small risks of stomach and gastrointestinal cancers have been attributed to consumption of waterborne radon.10
How is radon in air or water measured?
The amount of radon in air or water is measured in Picocuries/Liter (pCi/L). The Environmental Protection Agency has set 4 pCi/L as the guideline level for airborne residential radon. During water use small amounts of radon can be released into the air (10,000 pCi/L in water contributes an estimated 1 piCi/L to air). The American Cancer Society Cancer Prevention Study found a 34 percent increased risk of death from lung cancer among participants exposed to mean radon concentrations above this 4 pCi/L level.12 While 4 pCi/L is a threshold used to identify those at the highest priority for exposure reduction,
levels below 4 pCi/L still pose a health risk10, and it is thought that lung cancer risk actually increases incrementally with the amount of radon exposure.2 Attempts have been made to predict which homes in the state are likely have the highest radon levels based on the underlying geology. A study conducted in 2006 revealed only modest correlations between the soil types in New Hampshire and the actual observed shortterm residential radon levels. These data emphasize the importance of measuring radon levels in each home, rather than relying on predictions or assumptions. A number of factors besides soil type can influence residential radon levels, including home construction.13 Although granite can be a source of radon, granite countertops are unlikely to cause high radon levels in a home.14 Likewise, building materials are not usually a significant source of radon.10 Use of radon resistant building practices should be considered during new home construction.15 These practices include installing a layer of gravel covered with plastic sheeting underneath the home, sealing cracks in the foundation to prevent radon entry, and running a vent pipe from the gravel layer through the roof to remove any gas.15
How to test for residential radon exposure
Radon testing is recommended for all New Hampshire homes (test kits are available through home improvement stores and the National Radon Program Services).16 The U.S. Surgeon General and the Environmental Protection Agency recommend that all residences below the third floor level be tested for radon.17 Several different types of tests measure the amount of radon in the air: • A short term evaluation can be performed by placing a charcoal canister test device in the lowest living area of the home, usually for approximately one week. • Long-term tests over a 3-12 month period provide a more accurate estimate of exposure because levels fluctuate over time. Long-term assessments should include the winter months, when the radon may accumulate to higher levels because houses are sealed to minimize heat loss. Various remediation strategies can be used to reduce exposure in existing homes with elevated radon levels. Sealing basements with plastic sheeting and caulking cracks can help prevent radon gas entry, however these measures are not usually sufficient long-term. Installing pipes and exhaust fans can vent the radon gas from the home (the average cost of installing such a system to reduce indoor air radon levels is $1,200).16 To learn more about radon in New Hampshire go to: http://des. nh.gov
NH Comprehensive Cancer Collaboration in partnership with Norris Cotton Cancer Center at Dartmouth-Hitchcock
Together-Eliminating Cancer
August 2013
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10. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for radon. In: Services USDoHaH, editor. Atlanta, GA2012. 11. Lantz PM, Mendez D, Philbert MA. Radon, smoking, and lung cancer: the need to refocus radon control policy. Am J Public Health. 2013;103(3):443-7. 12. Turner MC, Krewski D, Chen Y, Pope CA, 3rd, Gapstur S, Thun MJ. Radon and lung cancer in the A merican Cancer Society cohort. Cancer Epidemiol Biomarkers Prev. 2011;20(3):438-48. 13 Shi X, Hoftiezer DJ, Duell EJ, Onega TL. Spatial association between residential radon concentration and bedrock types in New Hampshire. Environ Geol. 2006;51(1):65-71. 14. Allen JG, Zwack LM, MacIntosh DL, Minegishi T, Stewart JH, McCarthy JF. Predicted indoor radon concentrations from a Monte Carlo simulation of 1,000,000 granite countertop purchases. J Radiol Prot. 2013;33(1):151-62. 15. EPA. Radon Resistant New Construction. United States Environmental Protection Agency; 2013 [updated 2013; cited 2013]; Available from: http://www.epa.gov/radon/rrnc/index.html. 16. Kansas State University. National Radon Program Services. 2013 [updated 2013; cited]; Available from: http://sosradon.org/test-kits. 17. EPA. Radon. United States Environmental Protection Agency; 2013 [updated 2013; cited 2013]; Available from: http://www.epa.gov/ radon/states/newhampshire.html.
