Our world today is concerned about environmental pollution. And this is understandable - the composition of the air that we breathe, and the food that we consume has long ceased to be environmentally friendly. Since the first test of nuclear weapons (1945), our planet has been contaminated with various radionuclides with anthropogenic properties. And one of them is cesium-137. Its half-life is huge, and the impact on the human body is 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 an atomic number 55. The chemical symbol of the element is Cs (Caesium), and it got its name due to the presence in the spectrum of the relative intensity of electromagnetic radiation of two blue lines (from the Latin word caesius which means "sky blue").
As a simple substance, cesium is a soft silver-yellow metal with pronounced alkaline characteristics.
This element was discovered in 1860 by two scientists from Germany R. Bunsen and G. Kirchhoff. They used the spectral analysis method, and cesium was the first element that was discovered by this method.
The many faces of cesium
In nature, cesium occurs exclusively in the form of the stable isotope 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 Cs-135 isotope lives the longest (up to 2.3 million years), and the second half-life is the cesium-137 isotope. 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 in testing weapons with nuclear warheads.
Unstable radionuclide
As a result of the half-life of cesium-137, it goes through a beta decay stage and turns into unstable barium-137m, and then into stable barium-137. In this case, gamma radiation is released.
It is the full half-life of cesium-137 that is 30 years, and before barium-137m it decays in 2.55 minutes. The total energy of this process is 1175.63 ± 0.17 keV.
The formulas describing the half-life of cesium-137 are complex and are 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 chemical properties, this element is close to rubidium and potassium.
All isotopes (including cesium-137 with a half-life of 30.17 years) when ingested in a living organism in any way are perfectly absorbed.
Leading supplier of biosphere radionuclide
The source of the biosphere radioactive nuclide of cesium-137 with a half-life of more than 30 years is nuclear energy.
Statistics is inexorable. According to 2000 data, about 22.2 × 10 19 Bq of cesium-137, with a half-life of more than 30 years, was released into the atmosphere by all reactors of nuclear power plants in the world.
Not only the atmosphere is polluted. From tankers and icebreakers with nuclear installations, from nuclear submarines, this radionuclide enters the ocean annually. Thus, according to experts, during the course of the operation of one submarine reactor, about 24 x 10 14 Bq will fall into the ocean within one year. Given the half-life of cesium-137, this becomes a dangerous source of very long-term environmental pollution.
The most famous emissions
Before proceeding to the effects of radionuclide cesium on the human body, we recall a few major disasters, accompanied by the release of this element into the biosphere.
Few people know, but in 1971, in the Ivanovo region (Galkino village), work was carried out on the deep sounding of the crust of our planet. These were underground nuclear explosions, after one of which a mud fountain broke out of one well. And today, at the site of these works, radiation of 3 milli-x-rays per hour is recorded, and the strontium-90 and cesium-137 radionuclides are still reaching the Earth's surface.
Everyone knew about the disaster in Chernobyl in 1986. But not everyone knows that then about 1850 Pbq of radiation elements entered the atmosphere. And 270 Pbq of them - cesium-137.
In 2011, when the accident occurred at the Japanese Fukushima nuclear power plant, 15 PBq of cesium-137 with a half-life of 30 years entered the Pacific Ocean.
What happens then
With radioactive fallout and waste, cesium-137 enters the soil, from where it enters plants, in which its absorption coefficient is observed at the level of 100%. In this case, up to 60% of the nuclide accumulates in the aerial parts of the plant organism. Moreover, in soils poor in potassium, the effect of accumulation of cesium-137 increases markedly.
The highest accumulation rates of this nuclide are noted in freshwater algae, lichens and plant organisms in the Arctic zone. In the body of animals, this radionuclide accumulates in the muscles and liver.
Its highest concentrations were observed in reindeer and waterfowl of the Arctic coasts.
Accumulate cesium and mushrooms. Especially butterfish, Polish mushrooms, moss-flies and sows throughout the half-life.
Biological properties of cesium-137
Natural cesium is one of the microelements of the animal organism. In our body, cesium is contained in an amount of 0.0002-0.06 μm per 1 gram of soft tissue.
The cesium radionuclide, as already mentioned, is included in the cycle of substances in the biosphere and moves freely along biological trophic chains.
When ingested orally in the gastrointestinal tract, 100% absorption of this nuclide occurs. However, in different departments the speed of this process is different. So, an hour after ingestion, up to 7% of cesium-137 is absorbed in the human stomach, up to 77% in the duodenum, jejunum and ileum, in the cecum - up to 13%, and in the last part of the intestine (transverse colon) - up to 40%.
The proportion of cesium-137 that enters through the respiratory tract is 25% of the amount received from food.
Through the blood to the muscles
After reabsorption in the intestine, cesium-137 is approximately evenly distributed in the tissues of the body.
Recent studies in pigs have shown that this nuclide reaches its highest concentration 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%.
- Lungs - 55%.
- Liver - 48%.
The elimination half-life makes from 5 to 14 days and is carried out mainly with urine.
What happens in the human body
The main pathways for cesium to enter the body are through the digestive tract and respiratory tract. With external contact with intact skin, cesium-137 penetrates 0.007%. When ingested, 80% of it accumulates in skeletal muscle.
The element is excreted through the kidneys and intestines. Within a month, up to 80% of cesium is excreted. According to the International Commission on Radiological Protection, the half-life of a radionuclide is seventy days, but the speed depends on the condition of the body, age, nutrition and other factors.
Radiation lesions, similar in symptoms to radiation sickness, develop when a dose of more than 2 Gy is received. But even with units of MBq, there are signs of mild radiation damage in the form of diarrhea, internal bleeding, and weakness.
How to protect yourself from infection
To determine the amount of cesium-137 in the human body, beta-gamma radiometers or human radiation counters (WMS) measure gamma radiation from the body or from excreta.
When analyzing spectrum peaks that correspond to a given radionuclide, its activity in the body is determined.
Prevention of infections with liquid or solid compounds of cesium-137 consists in carrying out manipulations exclusively in airtight boxes. To prevent the element from getting inside, personal protective equipment is used.
It should be remembered that the half-life of cesium-137 is 30 years. So, in 1987 in Brazil (the city of Goiania), the theft of parts from a radiotherapy unit occurred. Within 2 weeks, about 250 people were infected, four of them died within a month.
Permissible standards and emergency care
The allowable income of this element is considered 7.4 x 10 2 Bq during the day and 13.3 x 10 4 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 10 2 Bq per liter.
If these standards are exceeded, measures must be taken to accelerate the elimination of the element from the body. First of all, measures should be taken to decontaminate surfaces (face and hands) with soap and water. If substance enters through the respiratory tract, rinse the nasopharynx with saline.
The use of sorbents and diuretics with a water load will accelerate the elimination of the element.
In severe cases, hemodialysis is performed and specific therapy is prescribed.
But there is a benefit
In chemical research, gammodefectoscopy, in radiation technologies and in conducting various radiobiological experiments, scientists have found application to this anthropogenic 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 of radioisotope current sources and in the level meters of bulk solids, where it is used in opaque sealed containers.