Our world today is concerned about environmental pollution. And this is understandable - the composition of the air we breathe and the food we eat have long ceased to be environmentally friendly. Since the first test of nuclear weapons (1945), our planet has been polluted with various radionuclides with anthropogenic properties. And one of them is cesium-137. Its half-life is huge, and the effects on the human body are diverse. We will talk about this and much more in this article.
One of many
Cesium in the periodic table of Dmitry Mendeleev belongs to the main subgroup of the first group of the sixth period and has atomic number 55. The chemical symbol of the element is Cs (Caesium), and it got its name due to the presence of two blue lines in the spectrum of the relative intensity of electromagnetic radiation (fromthe Latin word caesius, which means "sky blue").
As a simple substance, cesium is a soft, silvery-yellow metal with pronounced alkaline features.
This element was discovered in 1860 by two German scientists R. Bunsen and G. Kirchhoff. They used the method of spectral analysis, and cesium was the first element to be detected in this way.
Many faces of cesium
In nature, cesium occurs exclusively as a stable isotope of Cs-133. But modern physics knows 39 artificially created radionuclides (radioactive isotopes).
Recall that isotopes are varieties of an atom of an element with a different number of neutrons in their nuclei.
The isotope Cs-135 lives the longest (up to 2.3 million years), the second in terms of half-life is cesium-137. It is the latter that is responsible for the radiation pollution of our planet. The half-life of cesium-137 in seconds is 952066726, which is 30.17 years.
This isotope is formed during the decay of nuclei in a nuclear reactor, as well as during testing of weapons with nuclear warheads.
Unstable radionuclide
As a result of the half-life of cesium-137, it goes through the beta decay stage and turns into unstable barium-137m, and then into stable barium-137. This releases gamma radiation.
It is the full half-life of cesium-137 is 30 years, and to barium-137m it decays in 2.55 minutes. The total energy of this process is1175.63 ± 0.17 keV.
The formulas describing the half-life of cesium-137 are complex and part of the decay of uranium.
Physical and chemical properties
We have already written about the physical properties of the isotope and the features of its decay. In terms of chemical properties, this element is close to rubidium and potassium.
All isotopes (including cesium-137 with a half-life of 30.17 years) are perfectly absorbed by any means when they enter a living organism.
Main supplier of biospheric radionuclide
The source of the biospheric radioactive nuclide cesium-137 with a half-life of more than 30 years is nuclear power.
The statistics are relentless. According to 2000 data, about 22.2 × 1019 Bq of cesium-137, whose half-life is more than 30 years, was emitted into the atmosphere by all reactors of nuclear power plants of the world.
It's not just the atmosphere that gets polluted. From tankers and icebreakers with nuclear power plants, from nuclear submarines, this radionuclide enters the ocean every year. Thus, according to experts, during the operation of one submarine reactor, about 24 x 1014 Bq will enter the ocean in one year. Given the half-life of caesium-137, it becomes a dangerous source of very long-term environmental pollution.
The most famous blowouts
Before we turn to the effects of radionuclide cesium on the human body, we recall several major disasters,accompanied by emissions of this element into the biosphere.
Few people know, but in 1971, in the Ivanovo region (the village of Galkino), work was carried out on deep probing of the crust of our planet. These were underground nuclear explosions, after one of which a mud fountain escaped from one well. And today, at the site of these works, radiation of 3 milliroentgens per hour is recorded, and the radionuclides of strontium-90 and cesium-137 still come to the surface of the Earth.
Everyone knows about the Chernobyl disaster in 1986. But not everyone knows that at that time about 1850 PBq of radioactive elements entered the atmosphere. And 270 PBq of them is cesium-137.
In 2011, when the accident occurred at the Japanese nuclear power plant "Fukushima", 15 PBq of cesium-137 with a half-life of 30 years, entered the waters of the Pacific Ocean.
What happens next
With radioactive fallout and waste, cesium-137 enters the soil, from where it enters plants, which have an absorption coefficient of 100%. At the same time, up to 60% of the nuclide accumulates in the aboveground parts of the plant organism. At the same time, in soils poor in potassium, the effect of accumulation of cesium-137 increases markedly.
The highest accumulation coefficients of this nuclide are noted in freshwater algae, lichens and plant organisms of the Arctic zone. In the body of animals, this radionuclide accumulates in the muscles and liver.
Highest concentrations have been seen in reindeer and waterfowl on Arctic coasts.
Accumulate cesium and fungi. Especially oil mushrooms, Polish mushrooms, mossiness mushrooms and pigs throughout the entire half-life.
Biological properties of cesium-137
Natural cesium is one of the trace elements of the animal body. In our body, cesium is contained in an amount of 0.0002-0.06 microns per 1 gram of soft tissues.
The cesium radionuclide, as already mentioned, is included in the cycle of substances in the biosphere and moves freely along biological trophic chains.
After oral contact with the human body in the gastrointestinal tract, 100% absorption of this nuclide occurs. However, the speed of this process is different in different departments. So, an hour after entering the body, up to 7% of cesium-137 is absorbed in the human stomach, up to 77% in the duodenum, jejunum and ileum, up to 13% in the caecum, and in the last section of the intestine (transverse colon) - up to 40%.
The share of cesium-137 that enters through the respiratory tract is 25% of the amount that comes from food.
Through the blood to the muscles
After being reabsorbed in the intestines, cesium-137 is approximately evenly distributed in body tissues.
Recent studies in pigs have shown that this nuclide reaches the highest concentrations in muscle tissue.
When studying reindeer, it was found that cesium-137 after a single injection is distributed as follows:
- Muscles - 100%.
- Kidneys – 79%.
- Heart - 67%.
- Light – 55%.
- Liver- 48%.
The half-life is 5 to 14 days and is predominantly excreted in the urine.
What happens in the human body
The main ways of getting cesium into the body are through the digestive tract and respiratory tract. With external contact of cesium-137 on intact skin, 0.007% penetrates inside. When ingested, 80% of it accumulates in skeletal muscles.
The element is excreted through the kidneys and intestines. Within a month, up to 80% of cesium is removed. According to the International Commission on Radiological Protection, the half-life of a radionuclide is seventy days, but the rate depends on the state of the body, age, nutrition and other factors.
Radiation damage, similar in symptoms to radiation sickness, develops when receiving a dose of more than 2 Gy. But already at units of MBq, signs of mild radiation injury are observed in the form of diarrhea, internal bleeding, and weakness.
How to protect yourself from infection
To determine the amount of caesium-137 in the human body, beta-gamma radiometers or human radiation meters (HCR) measure gamma radiation from the body or from secretions.
When analyzing the spectrum peaks that correspond to a given radionuclide, its activity in the body is determined.
Prevention of infection with liquid or solid compounds of cesium-137 is to carry out manipulations exclusively in sealed boxes. Means are used to prevent the element from getting insidepersonal protection.
It is worth remembering that the half-life of cesium-137 is 30 years. So, in 1987 in Brazil (the city of Goiania) there was a theft of a part from a radiotherapy unit. Within 2 weeks, about 250 people were infected, four of them died within a month.
Tolerances and emergency care
Admissible receipts of this element are 7.4 x 102 Bq during the day and 13.3 x 104 Bq per year. The content in the air should not exceed 18 x 10-3 Bq per 1 cubic meter, and in water - 5.5 x 102 Bq per liter.
If the specified norms are exceeded, it is necessary to apply measures to accelerate the removal of the element from the body. First of all, measures should be taken to decontaminate surfaces (face and hands) with soap and water. If the substance enters through the respiratory tract, rinse the nasopharynx with saline.
The use of sorbents and diuretics with water load will speed up the removal of the element.
In severe cases, hemodialysis is performed and specific therapy is prescribed.
But there are benefits
In chemical research, gamma-ray flaw detection, in radiation technologies and in various radiobiological experiments, scientists have found use for this man-made element with radiating properties.
Cesium-137 is used in contact and radiation therapy, in the sterilization of medical instruments, food products.
This element has found its application in the manufacture ofradioisotope current sources and in level gauges of bulk substances, where it is used in opaque sealed containers.
