What the rays do to people

The enemy is invisible. It comes through the air, sneaks through leaky cracks in the windows and doors, people breathe in the air, cannot distinguish between good and bad air. After inhalation, the dangerous particles spread throughout the body. They can also enter the body through the skin. Then they accumulate in the tissue and unfold their destructive power.

20 years after the accident in Chernobyl, the most affected regions are recording a 40 percent increase in cancer patients.

However, what causes the body so much trouble is not the radioactive particles themselves. It is the so-called ionizing radiation that emanates from them. The radionuclide iodine 131, for example, is one of the beta-minus emitters. This means that electrons continuously shoot out of the nuclide into the environment. All biological molecules, including the water in the body, slow down this radiation. But this releases energy that can have an ionizing effect: It destroys the atomic shells of molecules and knocks out electrons in the process. This leaves behind chemically aggressive molecular residues. Experts speak of radicals.

In some cases, radicals do not cause any major damage, but the greater the ionizing radiation, the more radicals are produced. Then a kind of worst-case scenario can occur in the body itself: a dangerous chemical chain reaction begins, in which the charged particles react with each other to form stable compounds again. However, since these chemical reactions take place uncontrollably, compounds are sometimes formed that make no sense in the cell.

For example, ionizing radiation can render important enzymes inoperable or destroy entire cell building blocks - if the damage is too great, the cell dies. But the genetic material is also susceptible to ionizing radiation. If electrons are knocked out of the DNA molecule, this can lead to changes in the genetic information, which are passed on to the daughter cells during the next cell division. The greater the damage to the DNA, the higher the risk of cancer in the long term.

The body can deal with a lot of damage. Humans are exposed to natural radioactive radiation in the soil or atmosphere on a daily basis. However, the human organism has developed defense mechanisms to protect itself from these stresses. It can repair DNA damage or specifically break down damaged structures in the cell.

In the event of a disaster such as the one in Chernobyl, however, these natural protective functions reach their limits. The liquidators of Chernobyl, the hundreds of thousands of people who had to do the clean-up work after the reactor accident, were the hardest hit. According to estimates, 25,000 of them have already died in Russia alone. According to the International Atomic Energy Agency, 56 people died instantly. Most of them suffer from the consequences of radiation sickness, which occurs acutely after excessive radiation exposure.

Radiation sickness can occur with a short-term exposure of 0.25 sieverts. That's 250 millisieverts. By comparison, according to the Federal Office for Radiation Protection (BfS), the average pollution from the environment is currently about 2.1 millisieverts per year. A short-term exposure of four sieverts is considered fatal.

First symptoms: headache, nausea and vomiting

Radiation sickness has many faces. How severe it is depends on which tissue is affected by the radiation and to what extent. The first symptoms are headaches, nausea and vomiting. They occur a few hours after the body has been bombarded with radiation. Then they subside temporarily, only to return after a few days as loss of appetite, fatigue and malaise and last for a few weeks. People with such mild radiation sickness usually recover. However, the immune system often remains weakened for the rest of their lives, and those affected are more likely to struggle with infectious diseases.

It is still unclear how severe the radiation exposure of the people who had been in the immediate vicinity of the Fukushima reactor was. The people in the area can only hope that the government issued its warnings in time so that they could protect themselves from the radiation in their homes.

So far, there have been no official reports of severe radiation illnesses or even deaths. How agonizing an acute radiation sickness can end is shown by the victims of the atomic bombings in Hiroshima and Nagasaki and the Chernobyl disaster. Hair loss, uncontrolled bleeding, a destroyed bone marrow, coma, circulatory failure and other dramatic effects can bring death.

The best-known consequence is leukemia

But what if there are no immediate consequences? Then the danger is still not averted, because radiation physicians expect a risk of long-term effects from a dose of 0.2 sieverts. Because then the probability of DNA damage that the body can no longer repair is so high that cancer can develop over the years.

The best-known of all long-term effects is blood cancer, leukemia: The radionuclides strontium 90 and cesium 137 are deposited in the bone tissue and thus cause an increased risk of cancer. Experts like to call these substances bone-searching because the body confuses these substances with calcium and incorporates them into muscle and bone tissue during the usual physiological processes. This is particularly sensitive, because the formation of new blood cells takes place in the bone marrow. If ionizing radiation comes into play, blood cell formation can get out of control and lead to leukemia. At the same time, strontium 90 and cesium 137 also increase the risk of bone cancer.

In the face of these consequences, humans are as good as powerless. He can only try to keep the radiation exposure as low as possible by keeping a sufficient distance from the radiation source. In Japan, the area 20 kilometers around the reactor has already been evacuated. Some experts, however, say that a much higher radius is necessary.

According to reports, this substance could also have escaped from the Fukushima reactor, as so-called mixed oxide fuel elements, which also contain plutonium, have been used in reactor 3 of the power plant for several months. It is enough to inhale 40 billionths of a gram of it to cause an acute radiation dose of 15 millisieverts in the body. On the other hand, radioactive plutonium has a decisive advantage: it is one of the alpha emitters. This means that the radiation from the plutonium only reaches a few centimeters in the air and is completely retained, for example, by a sheet of paper or cloth gloves.

Iodine tablets protect - if they are taken in time

The population can protect itself somewhat better from the consequences of iodine 131 - with potassium iodide tablets, which Japanese authorities now want to make available to their population in sufficient quantities. The body stores iodine 131 in the thyroid gland, just like the non-radioactive iodine 127. Most of the Chernobyl fall-out fell over present-day Belarus in 1986. Ten years after the disaster, 424 children were diagnosed with thyroid cancer there. This corresponded to a frequency of 3.5 to 4 cancer cases per 100,000 children - ten times more than the global average.

However, iodine tablets only protect you if you take them in time, i.e. from contamination and in sufficient doses. In this way, the thyroid gland is saturated with iodine and does not store any further, radioactive iodine. However, it is unclear whether the population in the immediate vicinity could get the tablets in time.

At present, we can only speculate about the damage to health caused by the invisible enemy in Japan. It also depends on how the situation of the reactors will develop further and whether the worst fears of a worst-case scenario will still materialize.

Editor's note: An earlier version of the article had stated: "The inhalation of 40 billionths of a gram of plutonium 239 is sufficient to cause an acute radiation exposure of 15 millisieverts in the body. Then there is a severe radiation sickness that ends fatally within a few days." This information was incorrect. We apologize for the error.