The series "Chernobyl" caused a great response and spurred public interest in one of the worst disasters of the 20th century. Scientists from all over the world are watching its long-term consequences. Special attention is paid to the Exclusion Zone, the most contaminated with radionuclides. Now no more than two hundred people live there permanently. How experts assess their health and what geneticists have found out about the DNA of the local flora and fauna.
The scale of the disaster
The accident at the Chernobyl nuclear power plant is one of the most tragic pages in the history of the Soviet Union. The explosion, which thundered on the night of April 26, 1986, completely destroyed the reactor of the fourth power unit. 32 kilograms of radioactive material got into the atmosphere, including almost 18 kilograms of plutonium isotopes. The wind blew it all over long distances.
suffered Belarus, Ukraine and Russia. This is 280 million people, including 1.6 million children. Six hundred thousand liquidators were exposed to various doses of radiation. More than five million people still live directly in the contaminated territories.
After the accident, a forbidden zone with a radius of thirty kilometers was organized around the destroyed station. Within a few days, about ninety thousand people were evacuated from there. Then the zone was expanded by resettling the rest. The decommissioning of the Chernobyl nuclear power plant will take at least half a century, but for another thousand years the Exclusion Zone will be dangerous.
The exclusion zone of the Chernobyl nuclear power plant is located on the border of Ukraine and Belarus / Illustration by RIA Novosti. Source: Wikimedia maps | Map data & copy; OpenStreetMap contributors.
People return to the danger zone
A week after the accident, people began to return to Chernobyl, located 12 kilometers from the Chernobyl nuclear power plant, and the surrounding villages. All of them received housing outside the contaminated zone, but for various reasons could not settle there. They were mostly old people who were oppressed by the disorder in a new place and homesickness.
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Self-settlers live in conditions of an increased radiation background, which provides a unique opportunity to study how small radiation doses affect the body, to observe the long-term consequences of an accident.
Scientists constantly measure the level of radiation from houses, clothing, drinking water, soil. The most dangerous in the dwellings of self-settlers is furnace ash: it is a source of external and internal radiation. A lot of radiation enters the body from local food products - often the level of cesium-137 and strontium-90 in them greatly exceeds the norm. Mushrooms and fish are especially infected.
Self-settlers do not have radiophobia, but scientists are far from considering their health as normal. According to 1997 data, an increased mortality rate from oncology (27 percent) was observed in the infected zone, neurological disorders, mental borderline disorders were widespread, electroencephalography showed a deterioration in the state of the brain, an atypical decrease in alpha rhythms. The scientists who conducted the survey believe that radiation distorted the usual picture of aging.
A study of peripheral blood (from a finger) of self-settlers in 1998 and 2001 showed an increased level of leukocytes, chromosomes in cells of this type are damaged. These are signs of the action of ionizing radiation. As of 2013, approximately 180 self-settlers lived in the Exclusion Zone. The majority are middle-aged people, elderly, committed to the traditions and customs of the indigenous population of Polesie. Due to natural decline (since 1988 - by 85 percent), this small population with a unique lifestyle may disappear in ten to fifteen years, scientists at Sevastopol State University believe.
The average age of the remaining self-settlers - 73 years old / Illustration by RIA Novosti. Source: Omelchuk Yu. A., Lyamina N. V., Kucherik G. V. Environmental, industrial and energy security-2017. - 2017.
Scientists find genetic abnormalities
The soils and groundwaters of the Exclusion Zone are contaminated with various radionuclides, of which the most dangerous are long-lived cesium-137, strontium-90, americium-241 and isotopes of plutonium (the half-life of 239Pu is 24.1 thousand years).
It has long been known that ionizing radiation damages DNA. If the dose is significant, the hereditary material does not have time to recover, numerous errors arise - mutations that lead to the suppression and death of cells, the appearance of tumors.
A lot of works have been devoted to the study of the genome of flora and fauna in the infected zone, a large amount of data has been accumulated, but scientists do not dare to draw unambiguous conclusions. For example, in 2017, an article was published where the genetic diversity of small rodent voles in a zone was associated with a high rate of gene mutations due to radiation. Other scientists cite similar data. And yet there are more questions than answers.
For example, scientists from the EU and the USA believe that the observed effect can be explained by the increased migration of voles to a territory free from people or an increase in the antioxidant defense of cells and DNA repair in response to constant radiation and the accumulation of mutations. Even heteroplasmy, when there are different DNAs in one cell, is not associated with radiation. Without civilization, the Exclusion Zone has become a wilderness kingdom. The number of wild boars, deer, elk, storks, foxes, and rodents there has increased many times over. Rare species of birds have chosen local forests to create pairs: white-tailed eagles, owls, spotted cranes live here. At the same time, scientists from the All-Russian Research Institute of Radiology and Agroecology (Obninsk) in 2008 noted that chronic irradiation suppresses the immunity of animals and plants, and this leads to the spread of infections, the inability of forests to resist pest beetles. Due to the increased horizontal gene transfer, the number of mutations in microorganisms increases, new pathogenic strains appear. There is a risk of them leaving the zone. Another assumption: due to damage to the genome, plants and animals reproduce worse, which means that their number grows due to migration from outside. In general, how exactly chronic exposure regulates the life of the populations of flora and fauna in the zone remains unclear.
What does the increase in the number of cancer diseases indicate?
There are a lot of stereotypes around the Chernobyl accident, which is explained by the fear of exposure. At the moment, the only phenomenon that is clearly directly associated with radiation is the increase in the incidence of thyroid cancer. This is caused by exposure to the isotope iodine-131, the level of which in the air and milk was increased in the first days after the accident. In 1990, doctors began to more often detect thyroid cancer in children; in 1996, this growth stopped, but the incidence is still higher than among the population that has not been exposed to radiation. In total, 5,000 cases of thyroid cancer in Russia, Belarus and Ukraine are associated with radiation. By the way, in France this figure is higher. Some researchers note that this country is the leader in the number of nuclear power plants per capita. However, the incidence of thyroid cancer among women in South Korea is seven times higher,than in Belarus. Contrary to popular belief, there was no spike in malformations after the accident. It was the same after the atomic bombings of Hiroshima and Nagasaki in Japan. Nine months after the accident, an increase in the number of children with Down syndrome was recorded in Minsk, Gomel and West Berlin. But the reasons for this are unclear. Meanwhile, many works indicate a high percentage of damage and instability of the genome not only in flora and fauna, but also in people in the Exclusion Zone, in contaminated areas and in children born to liquidators. Researchers from Russia and Croatia, referring to the experience of Hiroshima and Nagasaki, note that the generation of children whose parents survived the catastrophe are more painful. But to what extent is radiation responsible for this? There is no definite answer. Scientists are increasingly emphasizing that, in addition to exposure to radiation,the accident at the Chernobyl nuclear power plant led to large-scale and profound socio-economic, psychological and environmental consequences. Tatiana Pichugina