Hello Hello,
I hope you're doing well and enjoying the beginning of winter. I also hope that you'll find the following
article about the health effects of radon by Dr. Harriet Burge both interesting
and useful.
With best wishes,
Dave Gallup
Health Effects of Radon
By Dr. Harriet Burge, EMLab P&K Chief Aerobiologist and Director of Scientific Advisory Board
Radon is one of the "noble" gases (such as neon and argon). It is a naturally occurring
element that is produced from radium which is part of the uranium decay series. Radon has a
half-life of 3.82 days and during decay produces particles called radon daughters. These particles
are solid, short-lived radioisotopes that emit alpha particles. When the radon daughters release
these alpha particles into the lungs, the alpha particles penetrate cells and cause DNA damage.
Exposure To Radon
Radon is measured in Becquerel's/cubic meter (Bq/m3). Concentrations may also be
reported in picocuries/liter (pCi/L) or picograms per cubic meter (pg/m3). One Bq
represents the activity of a radioactive material in which one nucleus decays per second. One
Bq/m3 is equal to 0.02 pCi/L and 0.0002 pg/m3.
Approximations of the dose of radiation received are reported as millirems (mrem) and "effective
dose" as milliSieverts (mSv). A millirem of radiation carries the risk of a 1 in 8 million
chance of dying of cancer (assuming one can extrapolate from very large to very small doses linearly).
The mSv represents 100 mrem. Another measure for dose of radiation is the Working Level Month (WLM)
or an average concentration of 1 Working Level (WL) for 170 hours. One WL = 8000 Bq/m3
or 200 pCi/L.
Radiation doses from radon progeny comprise more that 50% of the US population's exposure to
radiation. Medical X rays provide the second highest exposure (11%). Typical indoor residential
exposure is normally less than 400 Bq/m3 (generally about 100 Bq/m3) and
between 10 and 20 Bq/m3 outdoors. In houses built on soils with a high uranium content,
very high radon concentrations (>1000 Bq/m3) have been found.
Radon is also found in the ground, soil, rock and water. Homes that rely on well water may be
exposed to some additional radon if the concentration in the well is high. However, the greatest
health effect from this source is inhalation of the radon that transfers from the water to the
air, and only a very small fraction of the radon in water enters the air. The EPA has recommended
a standard for drinking water of 11Bq/L.
Health Effects of Radon
Lung cancer
The primary health effect of radon is lung cancer. When the radon daughters release these alpha
particles into the lungs, the alpha particles penetrate cells and cause DNA damage. The damage
is cumulative and can eventually cause cancer. Animal studies have shown that radon can cause
cancer without the contribution of other pollutants (e.g., tobacco smoke).
The fact that radon exposure causes lung cancer was recognized first in uranium miners. One study
evaluated American Indian miners who were non-smokers, and found a threefold increase in lung
cancer over that experienced by non smokers who were not miners in the same community.
Smoking increases the risk of lung cancer dramatically. Early evidence for the role of smoking
is the fact that before manufactured cigarettes were available, lung cancer was considered a
rare disease (in spite of ongoing exposure to radon). Following the introduction of manufactured
cigarettes, the incidence of lung cancers rose quickly to the point where it is now one of the
most common cancers. For lifelong non-smokers, absolute risks (as opposed to excess risk due
only to radon) of lung cancer (for those still alive) are 0.4%, 0.5% and 0.7% respectively at
radon concentrations of 0, 100 and 400 Bq/m3. In cigarette smokers exposed to the
same radon concentrations, these risks are 10%, 12% and 16% (Darby et al., 2005).
The EPA is strongly focused on the reduction of radon exposure primarily because of the enormous
public health impact of its role in lung cancer in smokers. Mendez et al. (2009) analyzed smoking
trends in the US and concluded that a better approach would be to concentrate on programs to
reduce smoking.
Radon and Childhood Leukemia
There is some evidence that excessive radon exposure can increase the risk of acute lymphoblastic
leukemia in children. One study demonstrated a 56% increase in the rate of this type of leukemia
per 1000 Bq/m3-years increase in exposure (Raaschou-Nielsen et al., 2008; Harley &
Robbins 2009).
Radon and Pancreatic Cancer
Radon exposure may be a significant risk factor for pancreatic cancer in African Americans,
American Indians, and Asian Americans. Testing and mitigating homes for indoor radon may decrease
the incidence of pancreatic cancer in these groups (Reddy & Bhutani 2009).
Radon and Other Cancers
One study of miners revealed some evidence for a relationship between other pulmonary cancers
and cumulative radon exposures, but unknown factors could have influenced their results either
negatively or positively (Kreuzer et al. 2008).
Protective Effect of Radon
There is some evidence that exposure to very low levels of radon may be protective, especially
in smokers. Samet (2009) suggests that a non-threshold linear response is indicated by studies
showing that a single alpha particle hit can permanently damage a cell. However, modeling of
data from miners' studies indicate that the excess risk for lung cancer at 100 Bq/m3
is 0.l6, indicative of a protective effect. Note that risk estimates relate to 1 (no
change), with estimates greater than 1 indicating increased risk and estimates less than 1
indicating decreased risk (Bogen 1998).
Standards and Guidelines
An indoor air radon concentration of 200-400 Bq/m3 has been adopted as an action or
reference level by many countries. Levels less than 160 Bq/m3 indicate that no further
action is necessary. The USEPA recommends remedial action if radon levels exceed 4 pCi/L (200
Bq/m3). The World Health Organization recommends a reference level of 100 Bq/m3
for radon. An acceptable radon concentration in the workplace is set at 1/3 of a WL or about
1200 Bq/m3. In September 2009, the World Health Organization released a comprehensive
global initiative on radon that recommended a reference level of 100 Bq/m3 for radon
and urged member countries to establish or strengthen radon measurement and mitigation programs,
as well as develop building codes that require radon prevention measures in homes under construction.
References:
1. EPA: A Citizen's Guide to Radon, What Your Test Results Mean.
Last updated on September 25, 2009.
2. Bogen KT. (1998). Mechanistic model predicts a U-shaped relation of radon exposure to lung
cancer risk reflected in combined occupational and US residential data. Human & Experimental
Toxicology 17(12): 691-696.
3. Darby S, Hill D, Auvinen A, Barros-Dios JM, Baysson H, Bochicchio F, Deo H, Falk R, Forastiere F,
Hakama M, Heid I, Kreienbrock L, Kreuzer M, Lagarde F, Mäkeläinen I, Muirhead C, Oberaigner W,
Pershagen G, Ruano-Ravina A, Ruosteenoja E, Schaffrath Rosario A, Tirmarche M, Tomášek L,
Whitley E, Wichmann H-E, and Doll R. (2005). Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies.
BMJ 330: 223.
4. Harley NH, Robbins ES. (2009). Radon and leukemia in the Danish study: Another source of dose.
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5. Bala´sha´zy I, Farkas A, Gergely Madas B, and Hofmann W. (2009). Non-linear relationship of cell
hit and transformation probabilities in a low dose of inhaled radon progenies. J. Radiol. Prot. 29 147-162.
6. Kreuzer M, Walsh L, Schnelzer M, Tschense A, Grosche B. (2008). Radon and risk of extrapulmonary cancers:
results of the German uranium miners' cohort study, 1960-2003. British Journal of Cancer 99(11): 1946-1953.
7. Mendez D, Alshanqueety O, Lantz P, Warner K. (2009). The impact of declining smoking on radon related
cancer in the US. 42nd Annual Meeting of the Society for Epidemiologic Research: Jun 23-26, 2009
Anaheim CA. American Journal of Epidemiology 169: S39-S39.
8. Raaschou-Nielsen O, Andersen CE, Andersen HP, Gravesen P, Lind M, Schuz J, Ulbak K. (2008).
Domestic radon and childhood cancer in Denmark. Epidemiology 19(4): 536-543.
9. Reddy NK, Bhutani MS. (2009) Racial disparities in pancreatic cancer and radon exposure: a
correlation study source. Pancreas 38(4): 391-395.
10. Samet JM, Avila-Tang E, Boffetta P, Hannan LM, Olivo-Marston, Thun MJ, Rudin CM. (2009). Lung cancer
in never smokers: clinical epidemiology and environmental risk factors. Clin Cancer Res 15(18): 5626-45.
11. Thompson RE, Nelson DF, Popkin JH, Popkin Z. (2008). Case-control study of lung cancer risk from
residential radon exposure in Worcester County Massachusetts. Health Physics 94(3): 228-241.
12. Whicker JJ, McNaughton MW. (2009). Work to save dose: contrasting effective dose rates from radon
exposure in workplaces and residences against the backdrop of public and occupational regulatory limits.
Health Physics 97(3): 248-256.
13. Wilcox HB, Al-Zough M, Garner M, Jiang JH, Klotz JB, Krewski D, Nicholson WJ, Schoenberg JB,
Villeneuve PJ, Zielinski JM. (2008). Case control study of radon and lung cancer in New Jersey.
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