Radon causes lung cancer

Radon is a colourless and odourless noble gas that is present in the indoor air in homes and at workplaces. Approximately 50 per cent of the annual radiation dose received by Finns results from radon present in indoor air. Long-term exposure to high radon levels in the home considerably increases the risk of lung cancer. In Finland, approximately 300 people each year are diagnosed with radon-induced lung cancer.

Decay products of radon in the air are inhaled into the lungs. They stick to the inner surface of the lungs, emitting alpha radiation. The radiation dose received into the lungs increases the risk of lung cancer. Even a small radiation dose may cause cancer, albeit the probability is low. The longer the stay and the higher the radon level, the higher the risk.

In Finland, 2,000 cases of lung cancer are diagnosed each year, approximately 300 of them associated with exposure to radon. Next to smoking, indoor-air radon is the most important known cause of lung cancer. For smokers, the risk caused by radon is higher than for non-smokers. 

 According to a European collaborative study*, thirty years of living in an environment with a radon concentration of approximately 700 Bq/m3 doubles the risk of developing lung cancer by the age of 75. A regular smoker whose living environment has a low radon level has an approximately 10 per cent risk of developing lung cancer, whereas the risk for a non-smoker is only 0.5 per cent. 

Thus, in a radon concentration of 700 Bq/m3, the smoker’s risk is 2*10%, that is, 20%, and the non-smoker’s risk is also doubled to 1%. The lung cancer risk for a person who has quit smoking is between one and twenty per cent. After quitting smoking, the risk decreases over time.

* Darby et al. 2005. Radon in homes and risk of lung cancer: Collaborative analysis of individual data from 13 European case-control studies. British Medical Journal, 330, 23–227 

Table. The number of lung cancer cases resulting from different causes, and the contribution of radon in the radon concentration categories. The national average radon concentration is assumed to be 100 Bq/m3, and the number of annual lung cancer deaths is assumed to be 1,991 (statistics of the Finnish Cancer Registry from 2008). (Source: Mäkeläinen I. Kuka saa syövän radonista? Ympäristö ja terveys 2010: 3; 60–63)

 

Number of lung cancer deaths resulting from different causes

Radon concentration category Bq/m3  

Contribution of radon 

Proportion of population  

Proportion of exposure  

Only radon

Radon and tobacco  

No radon, no tobacco   

Only tobacco  

Total    

< 100

   7%

  72%

  34%

13

  82

165

1,073

1,332

 

100–199

18%

  17%

  26%

  9

  61

  40

  260

  370

200–399

30%

    8%

  21%

  8

  51

  18

  115

  191

400–

52%

    3%

  19%

  7

  45

    6

    40

    98

Total

14%

100%

100%

37

238

 228

1,488

1,991

 

According to current understanding, radon does not cause other health hazards in addition to lung cancer. It does not cause allergic reactions, dizziness, fatigue or other similar sensations. Furthermore, radon does not harm objects or food stored in an environment with a high radon concentration. When an object is taken away from that environment, the radon decay products accumulated on its surface disappear within a few hours. Radon has nothing to do with the phenomenon called earth radiation.

European Code Against Cancer (WHO)

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  • Eeva Salminen / Research Professor