What was the impact of the Chernobyl disaster in Europe?
On the 26th of April in 1986, a nuclear reactor exploded in the Chernobyl power plant after an experiment was conducted against safety directions and probably due to imprecise orders from above. The reactor which exploded was one of the four reactors in the plant. The result was the worst and in fact the only full-scale accident in the history of nuclear power generation. Previously the worst accident had occurred at Three Mile Island in Pennsylvania, USA (1979), but that was contained by the walls of the reactor building. The Chernobyl accident was made much worse by the subsequent inferno which was made possible by the fact that this was a graphite reactor, meaning that graphite rather than water was used to slow down the neutrons. This slowing down is necessary to maintain the chain reaction of nuclear fission. In western reactors, water is used for this purpose, and it cannot catch fire, of course.
Large emissions, wide-ranging fallout
Dust from the explosion travelled from Chernobyl mainly in a northwest trajectory towards Scandinavia, and reached the nuclear power plant of Forsmark in Sweden in about one day. There the dust cloud was turned by the winds to the northeast towards Finland which it crossed and whenever it happened to be raining, radioactive “hot particles” were deposited with the raindrops. These hot particles were, in fact, tiny pieces of the radioactive fuel.
Meanwhile at the site of the accident, the fire which was mainly due to the combustion of the graphite caused a huge plume of hot air to rise upwards, and the radioactive isotopes now boiling in the hot reactor were vapourized and carried away in the plume. Clouds of radioactive iodine and caesium and other isotopes were dispersed during the next couple of weeks, e.g. reaching the Nordic countries during the first half of May. The level of fallout was very different in different areas depending on where it happened to rain.
Most health effects are caused by radioactive iodine isotopes released in accidents. Its destructiveness is based on the fact that the tiny thyroid gland, weighing about 30 grams in adults, avidly gathers almost all of the iodine taken in by the body. The accumulation is especially effective if there has been a shortage of this trace element. This makes the concentration in the thyroid gland very high, and if the iodine is radioactive, then there is very intense local radiation in the gland itself. This is also the basis of radioiodine treatment of goitre. Instead of a surgical procedure, the overactive thyroid can be partly destroyed by the localized radiation without providing a very high radiation dose to any other parts of the body.
Radioactive iodine is fortunately rather short-lived; the half life of iodine-131 is only 8 days. Therefore the radioactivity disappears quite rapidly from the environment. An important isotope with a longer life is caesium-137 which has been calculated to have caused a 10 mSv  effective yearly dose in the worst-hit regions of Byelorussia and Russia. In Ukraine and Byelorussia, large amounts of iodine radioisotopes ended up in vegetables and on the grass pastures and in this way it gained access to cows’ milk. This contamination was not measured at the beginning, and the dairy products were not banned. Therefore children were exposed to very high concentrations of radioactive iodine, and this is believed to have resulted in four to five thousand thyroid cancers, but only a few of these children have died. Sadly, simple measures – use of iodine tablets, monitoring the foodstuffs and banning the use of local dairy produce would have prevented most of these children from contracting thyroid cancer.
Correcting error with another error
Caesium fallout may be calculated to have caused thousands of cancers in Ukraine, Byelorussia and Russia, but dissecting these cases from the much higher number of cancers from other causes will probably never be possible. One can protect oneself satisfactorily from exposure due to fallout by relatively simple measures, and this would have been much better for the health of the population than the panic-driven mass evacuations from the contaminated areas. This has lead to many social and psychological problems and the average health situation is worse among the evacuees as compared with those who stubbornly stayed at home against the official advice.
Exposure and effects in other countries
Finland received one of the higher doses of fallout in western Europe, so what is the situation here? Milk radioactivity did not increase much, because cows were still housed indoors at the time when the radiation was deposited in this northern country. Therefore the greatest problem is radioactive caesium - it will remain in the environment for many years to come. The highest human exposure has been from fish, mushrooms and other natural products. Nonetheless, the additional exposure due to the accident during the first year was only 5 % of the background radioactivity. Compared with radon  which accounts for about 50 % of radioactive exposure, the effect was minor. During the later years, the additional exposure has been less than 1 % of the background radiation.
In most other European countries, the radioactive exposure has been even less. While the yearly exposure in Finland after the initial peak has been 0.04 mSv (and remember that radon exposure is 2 mSv), the Dutch exposure has been estimated at 0.01 mSv, and in Portugal it is too close to zero to be differentiated from the background.
The most important protective measure is to monitor the radioactivity of certain foodstuffs, notably those obtained from the wild. In the case of fallout, the best protection is simply to stay indoors and follow the directions by authorities. There are studies showing that simple cover offers excellent protection. The explanation is that most of the radioactive materials will be falling with the rain, and the simplest roof will protect you both from the rain and the isotopes.
There have been various alarms raised about several cases of cancer, even in the same school class. In most cases, more detailed studies have revealed a single case of cancer that sparked the rumour, and often the types of cancers have not been those typical of radiation. Therefore most of the alarms seem to have been due to cancer cases occurring without a specific reason in the population. What has been clearly documented is the multitude of thyroid cancers occurring in children who were living in the worst iodine-contaminated areas. Even leukaemias, a type of cancer which is known to be sensitively related to the effects of ionizing radiation, have not been unequivocally attributed to radioactive fallout from the Chernobyl accident.
Nonetheless nuclear power production requires that the workers take the utmost care. It is the management’s duty to ensure they are well trained, motivated and behave responsibly. There is no room for improvisations in managing a power plant.
A nuclear accident is a disaster which is truly terrifying for good reasons. Nonetheless there are some simple preventive measures that can help an individual avoid many of the consequences of the calamity. Moreover, our current experience indicates that its health effects are less extensive in an organised and responsible society than the health effects of other sources of radiation or of some of the other ways used to produce energy.
Notes and references
- Sievert (Sv) is the unit of biologically effective dose of radiation. A lethal dose is about 3 to 5 Sv. Sievert is one thousand millisieverts (mSv).
- See the chapter “Is there radiation in my home?”
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