The miniseries Chernobyl (2019), co-produced by HBO (USA) and Sky (UK), recounts through the historical drama the nuclear disaster that occurred on April 26, 1986 at the Vladimir Ilyich Lenin nuclear power plant (Pripyat, USSR). It addresses many aspects, mainly on nuclear technology and safety or radiological protection. But perhaps what has most impacted viewers are the effects produced on the protagonists of the series who come to mitigate the consequences of the disaster: firefighters, soldiers, engineers, miners, scientists, etc. For this reason, this article will explain in a simple way what are the biological effects of ionizing radiation.
Ionizing radiation consists of electromagnetic waves (X and gamma rays) and charged particles (beta and alpha), emitted by unstable nuclei of atoms, which can tear electrons from the atoms of the medium through which they pass. This ionization of the environment, in our case the human body of the protagonists of the series, involves physical, physical-chemical, chemical and finally biological processes, which are manifested at the macroscopic level. These biological effects are classified as stochastic and deterministic. Let’s go on to describe them.
Stochastic effects occur at low radiation doses in which the cell does not die, but damage and changes occur, especially in the genetic material (DNA). The probability of their occurrence, not their severity, increases with the radiation dose received. The severity of its effects also depends on factors such as the type of cell that has been affected and the mechanism of the offending agent. The onset is late and can be somatic or hereditary in nature. It is somatic when the cell has been transformed after irradiation and the effect will be evident in the irradiated individual. It is hereditary if the modified cell is geminal, in which case it will not be revealed in the exposed individual but in progeny. The main known somatic effect is the development of cancer. In the series it is the case of two protagonists: the scientist Valeri Legásov and the politician Boris Shcherbina.
For deterministic effects to appear, the doses must be high, with the consequent death of a substantial number of cells. In this case, there are threshold doses: the higher it is, the more biological damage will occur. The appearance occurs immediately or after a short period of time. Due to the lethality that characterizes these effects, cell death is considered when the differentiated cells lose the function for which they are destined and when the dividing cells are not able to continue their proliferation or reproductive capacity. These effects are also known as Acute Irradiation Syndrome (AIS) and it depends on the dose received, the nature of the radiation, the body volume affected (there are more radioresistant and more radiosensitive), the exposure time, etc. The SIA is made up of three stages:
– Prodromal : these are the symptoms that appear in the first hours such as nausea, vomiting, vertigo, diarrhea, tachycardia, insomnia, etc.
– Latent : it is characterized by the absence of symptoms, can last for hours or weeks and is when changes occur in the affected organs that lead to recovery or definitive disease.
– Manifest disease : the specific symptoms of each organ system appear. The individual lives or dies. They can last from minutes to weeks.
These three stages are perfectly manifested in the case of the firefighter Vasili Ignatenko, who is one of the first to access the destroyed reactor and who receives extremely high radiation doses, along with his colleagues who come to put out the fire.
This little article would be incomplete if one does not talk about what the radiation dose is, even if it is intuited. Without specifying the types of doses that exist, we can borrow the general definition of absorbed dose given by the specialists of Foro Nuclear, a website for scientific dissemination on nuclear technology and radiological protection: “energy that deposits any ionizing radiation when passing through a unit of mass of the irradiated material, when a study of the biological effects produced by radiation on an individual tissue or organ is needed. It is a dosimetric quantity of great interest, because it is valid for any type of radiation. The unit in the International System is the gray (Gy), equivalent to the absorption of one joule per kilogram ”.
Antonio Javier Criado Martín is a professor of the Degree in Physics at UNIR and a member of the Spanish Society for Radiological Protection (SEPR)
