Which type of radiation poses the greatest threat to our health?

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Statistical threat

If existing statistics are taken as an indication of threat, the most dangerous kind of radiation is solar ultraviolet radiation (UV). Melanoma is one of the most dramatically increasing types of cancer in several countries, particularly those located in the north. In 2006, 62 000 new cases of melanoma were diagnosed in Europe (25 EU countries, Switzerland, Norway and Iceland combined). In several countries its incidence has increased by more than tenfold in the past 50 years. It is believed that the most important reason is excessive sunbathing.

One particularly worrying statistic is the high numbers of melanoma cases being diagnosed in the population under the age of 55 years, 21 000 new cancers in 2002 in Europe. This is thought to reflect cancers initiated at a young and adolescent age. Sunburns due to careless solar UV exposure increase the risk of melanoma substantially as well as the risk of other types of skin cancer. The most common of them is basal cell carcinoma (basalioma) which is more easily treated; its incidence is several-fold higher that of the much more deadly melanoma.

Also sunbeds are estimated to cause a number of melanomas, maybe a few per cent of those caused by outdoor sunbathing. Sunbeds cannot be recommended for anyone, least of all for young persons.[1]

Another common cause of environmental cancers is radon in homes. [2] A very large European study with over 7000 lung cancer patients and 14 000 controls suggested a risk increase of 8 % per 100 Bq/m3 of radon in the household air.[3] This is not a particularly high concentration, because the mean concentration in the homes of cancer patients was 104 Bq/m3, and in the homes of controls 97 Bq/m3. The additional risk is much greater for smokers who already have a high risk of lung cancer. The risk of smokers to contract lung cancer by the age of 75 years was calculated as 10 %, 12 % and 16 % with radon concentrations of 0, 100, and 400 Bq/m3. This translates into tens of thousands of lung cancers per year in Europe attributable to radon.

The additional risk of the Chernobyl accident outside Ukraine and Byelorussia is so small that it can never be shown by certainty in population-wide studies.[4] In Finland, which received one of the largest fallout deposits outside the Soviet Union, it has been calculated that the additional exposure to radioactivity was 5 % of the total exposure during the first year, thereafter less than one per cent. The best estimate of the cancers due to Chernobyl accident outside the then Soviet Union is 20 000 cases over 50 years. The uncertainty limits are, however, large.

Risk according to the type of radiation

The risk can be viewed from another standpoint. In some respects, the most dangerous radiation is alpha radiation, because it is very damaging to the tissue, on the other hand it does not penetrate very long distances into the tissue. Therefore radon is important for its risk of lung cancer, but it does not cause other cancers. The radiation of radon is restricted to the lungs.

High exposure

Radioactive iodine can also be very dangerous. This is based on the fact that iodine is concentrated very avidly into the thyroid gland. Therefore local exposure in that particular tissue is very high. This is why so many thyroid cancers were detected in the children in Ukraine and Byelorussia after the Chernobyl accident.[5] The saddest part of this tragedy is that most of those would have been avoided by preventing the consumption of contaminated food items such as milk after the radioactive fallout.

Thus the threat can be viewed from different perspectives. One kind of radiation may be worse than others. Radiation may be selective for one organ only, because it is concentrated there. Exposure may be more common for certain types of radiation because of their common occurrence in our environment. All these factors determine the total threat to the population.

The radiation threat is based on two different factors, how high is the exposure level, and how damaging to the tissues is that particular kind of radiation. The greatest risks are posed by radiation whose effects are not understood and they are often ignored, such as with sunlight. Therefore the exposure can be dangerously high.

Notes and references

  1. See the chapter “Should solariums carry a health warning?
  2. See also the chapter “Is there radiation in my home?
  3. Becquerel (Bq) is the unit of radioactivity, meaning disintegrations per second.
  4. See the chapter “What was the impact of the Chernobyl disaster in Europe?"
  5. See the chapter “What was the impact of the Chernobyl disaster in Europe?

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