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Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

Plutonium

  • Plutonium (Pu) is a heavy metal with the atomic number 94.
  • For the human body it is chemically toxic as some other heavy metals like lead and mercury.
  • Plutonium is not only hazardous to human health due to its chemical properties. It is also radioactive and thus causes also harmful radiation effects. They are most dangerous after inhalation.

Glossary Entry Radionuclide

A radionuclide is an instable nuclide which decays into another nuclide spontaneously without extraneous cause emitting energy-rich (ionising) radiation. Currently more than 3,300 different nuclides are known which distribute over 118 currently known elements. Of these nuclides more than 3,000 nuclides are instable and radioactive.

Glossary Entry Incorporation

Generally: uptake into the body. Especially: uptake of radioactive substances into the human body.

Plutonium is a heavy metal with the atomic number 94. For the human body it is chemically toxic as some other heavy metals like lead and mercury.

Additionally, plutonium is radioactive, which means that its various nuclides (238, 239, 240, 241, 242, 244) emit radiation during decay. The half-life of plutonium nuclides is rather long, for example for plutonium-239, it takes 24,110 years until half of the atomic nuclei have decayed. During radioactive decay, mainly alpha radiation is emitted and - to a far lesser extent - also gamma radiation.

Appearance, sources and properties of plutonium

Plutonium occurs in nuclear reactors when uranium-238 is exposed to a neutron flow inside the nuclear fuel rods. To this day, about one thousand tons of plutonium have been generated by military and civil activities. Large amounts of plutonium have been released to the environment during the above-ground nuclear weapon tests in the 1950s and 1960s (fall-out). Thus, about four tons of plutonium have been spread around the world. These are mainly the nuclides plutonium-239 and plutonium-240.

Natural sources of plutonium are very scarce. Traces of plutonium-244 occur in some minerals, for example.

The different plutonium isotopes can be detected by alpha and gamma spectrometry and by measuring the beta radiation of plutonium-241.

Nuclides of the element Plutonium
RadionuclideHalf-life
Pu-23887.74 years
Pu-23924,110 years
Pu-2406,563 years
Pu-24114.35 years
Pu-242 375,000 years
Pu-24480 million years

Medical-biological effects of plutonium

Plutonium is not only hazardous to human health due to its chemical properties. Its radioactivity may also cause harmful radiation effects due to alpha and gamma radiation. Depending on the route of incorporation, primarily inhalation and ingestion, different effects occur. Incorporation through open skin or wounds is also possible.

Effects after inhalation

Plutonium is most dangerous after inhalation. The solubility of the plutonium compounds determines how long the plutonium stays in the lung. A number of physical, chemical, and biological factors influence the retention time, which can be between about 100 and 10,000 days. After absorption in the lung, the plutonium is dispersed in the body and predominantly accumulates in the bones, the liver, and the airway lymph nodes.

Effects after food intake

After ingestion of plutonium with food, large parts are excreted with the faeces. The proportion of plutonium that is resorbed from food via the gastrointestinal tract depends mainly on the kind of plutonium compound and the person’s age. A rough estimate of the resorption rate of plutonium via foods is 0.05 per cent. For infants, this rate is supposed to be ten times higher. After resorption of plutonium through the gastrointestinal tract, it is dispersed in the body and accumulates primarily in the bones and the liver.

Of the plutonium absorbed through the blood, about 50 percent accumulates in the bones, 30 percent in the liver, and 20 percent in other tissues. The retention time of incorporated plutonium in the bones is about fifty to hundred years, and in the liver twenty to forty years, respectively.

Cancer risks

Because of the variable distribution of plutonium within the body as well as the differing retention times, the radiotoxicity of plutonium results in varying cancer risks. After inhalation, the risk of lung, bone, and liver cancer, and of leukemia is generally increased. After oral intake, risks of bone cancer, liver cancer, and leukemia are increased. After the intake of the same amount of plutonium activity through the breathing air, the risk of cancer can be about hundred times higher compared to the intake through food, depending on the chemical type.

Employees of the Soviet plutonium factory MAYAK, based in the Southern Ural, showed increased lung cancer mortality depending on the amount of plutonium they incorporated. Currently, a large internationally coordinated research program is conducted in the Southern Ural to better determine the health effects of plutonium incorporation, among others. Besides that, the assessment of radiation exposure from plutonium is being improved.

Sources of evidence

In addition to the results from that research, animal experiments and studies in individuals who were exposed to other alpha emitters than plutonium or to other forms of radiation are used to determine the detriment caused by plutonium.

State of 2017.07.11

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