Comparison of fallout from above-ground nuclear weapon tests, the reactor accident in Chornobyl, and the reactor accident in Fukushima

During above-ground nuclear weapons tests and reactor accidents radioactive materials are released into the atmosphere. This radioactive material can be deposited on earth, e.g. by precipitation (so-called fallout).

Above-ground nuclear weapon tests

Above-ground nuclear weapon tests resulted in the atmospheric release of the radioactive substances caesium-137 and strontium-90 in particular, as well as that of plutonium-239. These substances were dispersed around the globe and therefore also reached Germany, leading to an increased radiation dose for the general public. Precipitation washed the radioactive fission products out of the atmosphere (as "fallout") and deposited them on the ground. From there, they entered the human body via foodstuffs.

The Soviet Union, the USA and the United Kingdom signed a treaty banning nuclear weapon tests in the atmosphere, in outer space and underwater in 1963 and have carried out no further atmospheric tests. The agreement was also signed by numerous other countries (France and China did not sign and continued to carry out atmospheric nuclear weapon tests until 1974 and 1980 respectively). In subsequent years, the treaty led to a significant reduction in radiation dose.

Additional radiation dose due to nuclear weapon tests

For a person in the northern hemisphere, the total additional radiation dose (lifetime dose) due to atmospheric nuclear weapon tests is estimated to be approximately 4.4 millisieverts. The greatest additional radiation dose due to fallout from above-ground nuclear weapon tests was seen from 1963 to approximately 1967.

The few studies into the health effects of nuclear weapon tests have not identified any negative consequences

There are very few studies into the possible effects of above-ground nuclear weapon tests. One study from 2010 investigated whether it was possible to identify a significant impact of increased radiation dose due to nuclear weapon tests with respect to childhood leukaemia. This did not turn out to be the case. As the developing body of a child is particularly sensitive to radiation exposure, this finding suggests that it will not be possible to detect any health consequences of nuclear weapon tests in adults who were not in the direct vicinity of the test site.

In particular, no differences have been identified between the southern and northern hemispheres either. An increased risk of disease ought to have been most readily discernible in the northern hemisphere given that the additional radiation dose due to above-ground nuclear weapon tests was higher in the northern hemisphere than in the southern hemisphere.

Chornobyl reactor accident

Following the reactor accident in Chornobyl, radioactive fission products were transported via the air to large parts of Europe and therefore also to Germany. Above all, these were the radioactive substances iodine-131, caesium-134 and caesium-137. Practically no strontium-90 was detected in Germany.

Additional radiation dose due to the Chornobyl accident

In the one-year period immediately following the Chornobyl (Russian: Chernobyl) reactor accident, the greatest additional radiation dose in Germany due to the disaster was approximately 0.1 millisieverts per year north of the Danube and 0.3 millisieverts per year south of the Danube.

Epidemiological studies of the risk of disease due to the Chornobyl accident

Following the reactor accident in Chornobyl, numerous epidemiological studies were carried out with a view to detecting a possible increase in the risk of disease due to additional radiation dose.

• In some cases, severe health consequences were observed in workers and emergency service personnel who were involved in clean-up operations and had received a relatively high dose of radiation.
• A significant increase in cases of thyroid cancer was observed in individuals who were exposed to iodine-131 contamination as children and adolescents in the areas with the highest levels of radioactive contamination (Ukraine, Belarus and parts of Russia). This group of people is still subject to an increased risk today.
• For other types of cancer and leukaemia in these regions, there is still no reliable data concerning an increased risk. However, there are indications of a greater risk of leukaemia among the emergency service personnel and clean-up workers as well as a greater risk of breast cancer among women in Ukraine who received an additional radiation dose.

For Germany, there is still no evidence that increased radiation dose due to the Chornobyl reactor accident has resulted in adverse health effects. In particular, no evidence has been found in Germany of an increased incidence of thyroid cancer in children.

Although individual studies have identified corresponding indications with regard to infant mortality and the frequency of malformations and tumours in children or adults, the methodological weaknesses of these studies mean that the results cannot be taken as evidence of a link between radiation dose and these health effects.

The prevailing view among experts is that it is conceivable that Chornobyl has led to additional radiation-induced cases of cancer and other diseases. However, these will be practically impossible to detect – using existing scientific tools – against the backdrop of the "spontaneous" cancer incidence or the spontaneous rates of other diseases, on the one hand, and Germany's natural radiation dose of 2 to 3 millisieverts per year, on the other, as well as the different mechanisms of action of radiation depending on the disease.

Significantly lower radiation dose from the accident in Fukushima

The first evidence of radioactive substances from the reactor accident in Fukushima that had been transported to Germany via the atmosphere came around two weeks after the accident began. On 25 March 2011, the BfS measuring station on the Schauinsland mountain was the first to detect iodine-131 that could be attributed to the accident in Fukushima.

Given the very large distances involved, only a very small quantity of radioactive substances reached Germany. This corresponds to only a fraction of the quantity that was transported to Germany via the air in the past as a result of nuclear weapon tests and the accident in Chornobyl.

No health consequences of the accident in Fukushima are expected for Germany in the long term

No adverse health effects are to be expected for Germany, including in the long term, given that the radiation dose in the country due to the accident in Fukushima remained well below the dose due to nuclear weapon tests and the accident in Chornobyl.