Radiation can damage cells. Protection of the body copes with this, until the radiation doses exceed the natural background by hundreds and thousands of times. Higher doses lead to acute radiation sickness and increase the probability of cancer by several percent. Doses tens of thousands of times higher than the background are deadly. There are no such doses in everyday life.
The death and mutation of the cells of our body is another natural phenomenon that accompanies our life. In an organism consisting of approximately 60 trillion cells, cells age and mutate for natural reasons. Several million cells die every day. A lot of physical, chemical and biological agents, including natural radiation, also “spoil” the cells, but in normal situations, the body easily copes with this.
Compared to other damaging factors, ionizing radiation (radiation) has been studied best. How does radiation affect cells? When fissioning atomic nuclei, a large energy is released, capable of detaching electrons from the atoms of the surrounding matter. This process is called ionization, and the energy-carrying electromagnetic radiation – ionizing. Ionized atom changes its physical and chemical properties. Consequently, the properties of the molecule into which it enters are changed. The higher the radiation level, the greater the number of ionization events, the more damaged cells will be.
For living cells, changes in the DNA molecule are most dangerous. A damaged cell can be “repaired”. Otherwise, it will die or give an altered (mutated) offspring.
Dead cells are replacing the body with new ones for days or weeks, and the mutant cells effectively discards. This is the immune system. But sometimes protective systems fail. The result in a long time may be cancer or genetic changes in offspring, depending on the type of damaged cell (normal or germ cell). Neither one nor the other outcome is predetermined in advance, but both have some probability. Spontaneous cases of cancer are called spontaneous. If the responsibility of an agent is established for the occurrence of cancer, it is said that the cancer was induced.
If the dose of irradiation exceeds the natural background hundreds of times , it becomes noticeable to the body. It’s not that it’s radiation, but what is more difficult for the body’s defense systems to cope with the increased number of injuries. Because of the frequent failures, there are additional “radiation” cancers. Their number can be several percent of the number of spontaneous cancers.
Very large doses, this is thousands of times higher than the background. At such doses, the main difficulties of the organism are not associated with altered cells, but with rapid loss of tissues important for the body. The body does not cope with the restoration of the normal functioning of the most vulnerable organs, primarily the red bone marrow, which belongs to the hematopoiesis system. There are signs of acute malaise – acute radiation sickness. If the radiation does not kill all the cells of the bone marrow at once, the body will eventually recover. Recovery after radiation sickness does not take one month, but then a person lives a normal life.
Cured after radiation sickness, people are somewhat more likely than their non-irradiated peers to have cancer. How much more often? A few percent.
This follows from observations of patients in different countries of the world who have undergone a course of radiotherapy and received sufficiently high doses of radiation for employees of the first nuclear enterprises, which have not yet had reliable radiation protection systems, as well as for the survivors of the atomic bombardment by the Japanese, and Chernobyl liquidators. Among the listed groups, the highest doses were among Hiroshima and Nagasaki residents. Over 60 years of observations, 86.5 thousand people with doses 100 times or more higher than the natural background had 420 more deaths than in the control group (an increase of about 10%). Unlike the symptoms of acute radiation sickness, which manifest themselves in hours or days, the cancer does not appear immediately, maybe after 5, 10 or 20 years. For different cancer locations, the latent period is different. Most quickly, in the first five years, develops leukemia (blood cancer). It is this disease that is considered an indicator of radiation exposure at radiation doses hundreds and thousands of times higher than the background