Radiation damage
Radiation damage is damage caused by ionizing radiation to living beings or material. The radiation can come from natural or artificial sources. Neutron radiation only has an indirect ionizing effect, but also causes radiation damage. Radiation damage is sometimes also referred to as radiation . Resistance to radiation damage is called radiation resistance .
Because of the limitation to damage caused by ionizing radiation, “radiation damage” does not usually mean damage caused by the pure thermal effect of radiation (e.g. combustion (medicine) ).
When the radiation penetrates matter, it releases energy to the atoms or molecules it hits . Among other things, atoms are spatially displaced, electrons are knocked out of their atomic shells and chemical bonds are broken, creating radicals which in turn can cause damage.
Radiation damage in materials
In solid technical materials, such as metals, the knocking out of atoms from their crystal lattice places worsens the material properties. Such individual damage accumulates until there are finally visible changes (for example fading) and / or changes in the strength properties, often in the direction of embrittlement. The latter plays a role in particular in the case of irradiation with fast neutrons in nuclear reactors and future fusion reactors . This type of damage is offset damage or Displatzierungsschaden (Engl. Displacement damage ) and is usually in the unit displacements per atom (Engl. Displacements per atom , dpa) reported. Another type of structural damage caused by fast neutrons is the generation of the gases hydrogen and helium in the material through nuclear reactions of the type (n, p) or (n, alpha).
The ionizing effect of the radiation can also cause damage in the irradiated material, because it leads to the release of a more or less energetic charged particle , which in turn can release further charged particles.
In polymers , i.e. plastic materials, the molecules excited by the action of radiation form the starting point for a variety of subsequent reactions. For example, individual H atoms or entire side chains can be detached in polymers or the main polymer chain can be separated. Because of their greater mobility in the material, smaller fragments can react more quickly with other substances. The lifetime of the radicals depends heavily on the temperature of the irradiated material; warming up can therefore heal some radiation damage more quickly.
In semiconductor materials , as in metals, radiation damage occurs mostly through the displacement of lattice atoms in the irradiated material, which can lead to amorphization of the semiconductor and a change in conductivity . Accordingly, the radiation resistance of components and materials that are to be used in a special radiation environment is an important topic in materials research. Under certain circumstances, the generation of radiation damage can also be used constructively, e.g. B. in ion implantation for doping semiconductors.
Radiation damage to living things
Living organisms - just like humans - have complex repair systems that have so far only been partially understood that can reverse most of this damage. But here too, the remaining microscopic damage accumulates. In general, lower organisms such as bacteria can endure much higher doses of radiation than higher organisms such as mammals. The bacterium Deinococcus radiodurans can even live in the cooling water of nuclear reactors.
In most countries, radiation protection regulations regulate the handling of radiation and substances that emit ionizing radiation, and set limit values for the maximum exposure ( radiation dose ) to the population.
Radiation damage to humans and animals can be divided into:
- Somatic damage that occurs in the irradiated organism itself.
- Teratogenic damage that causes damage to the embryo during pregnancy.
- Genetic damage that only occurs in the offspring.
In terms of somatic damage, a distinction is made between early and late damage:
- Early somatic damage occurs after hours or at the latest after a few weeks (see radiation sickness ). This damage can only be medically proven if a minimum dose (threshold dose) of radiation has been absorbed, which for humans is between 200 and 300 mSv . Symptoms of illness are, for example, a changed blood count , nausea , inflammation of the mucous membranes or fever .
- Long-term somatic damage is only noticeable externally years or decades after the irradiation, although the cells were already damaged immediately after the irradiation. One can differentiate between malignant (such as leukemia ) and non-malignant long-term damage (such as infertility or clouding of the lens of the eye ) in late-stage damage .
Cell biological effects of radiation
Effects at the molecular level
If ionizing radiation hits an organism, DNA changes ( mutations ) can occur in the cell nucleus . When rays hit the DNA, both single and double-strand breaks in the nucleotide chains can occur directly . The indirect radiation effect also plays an important role. Here, radicals are formed from water molecules (OH and H radicals), which, along with other molecules, can attack deoxyribose , which leads to hydrolysis of the phosphoric acid ester bond. In addition, a radiation effect can take place on the nucleotide bases. This leads to ring openings and, in the presence of oxygen, to peroxide formation (e.g. thymine hydroxyhydroperoxide). Also, after radical formation, dimerizations of bases are possible, which lead to a spatial change in the double helix . During transcription , damage to the DNA can result in incorrect reading due to base damage or a stop in the event of single strand breaks. In the case of minor damage, however, an undisturbed transcription is also possible.
In addition to the effects of radiation on the DNA, the structure of proteins can generally be changed. This is important in the case of enzymes , which thereby lose their enzyme activity .
In a eukaryotic cell, most of the damage is repaired. If a wrong repair or no repair takes place, this has one of the following two consequences.
Cell death
The cell loses its ability to divide and dies at the end of its life. If a sufficient number of cells are affected, deterministic radiation damage results . Since cell death is a natural process in the cycle of a differentiated cell, a certain threshold dose is required before sufficient cells die and the harmful effect manifests itself as the affected tissue loses its function. The severity of the damage increases proportionally to the dose. The deterministic damage includes acute (early) damage ( e.g. erythema , acute radiation sickness ), non-cancerous late damage (fibrotic tissue changes, clouding of the lens of the eye, impaired fertility, testicular abnormality) and teratogenic effects (malformations of the child during pregnancy).
Cell change
The cell divides, but passes the modified DNA on to the daughter cells. The consequences are stochastic radiation damage . There is a certain probability that they will not appear until years or decades after exposure. There is probably no threshold dose for them; the likelihood of such damage occurring is proportional to the dose. The level of the dose does not affect the severity of the disease, only the probability of its occurrence. The stochastic radiation damage is decisive at low doses and for assessing the radiation risk in radiation protection . They have similar effects as random, spontaneously occurring DNA changes, for example cell transformations that lead to cancer , mutations and hereditary diseases , or also teratogenic effects.
Lethal dose for living things and viruses
The LD 50 | 30 values (50% lethality after 30 days, according to data from the IAEA ) for living beings and viruses differ greatly, since they show different sensitivity to ionizing radiation. As with radiation sickness, the values refer to short-term whole-body irradiation. Short-term means short in comparison with biological healing processes; an exposure duration of a few minutes is therefore “short”, one or several hours is no longer.
| Life form | Lethal dose LD 50 | 30 Gy |
|---|---|
| Guinea pig | 2.5-4 |
| goat | 3.5 |
| human | 3-4.5 |
| dog | 4-5.5 |
| Rhesus monkey | 5.5 |
| rat | 6th |
| Goldfish | 8.5 |
| hamster | 9-11 |
| Trout | 15th |
| Escherichia coli | 50 |
| bat | 50 |
| slug | 200 |
| wasp | 1,000 |
| Tobacco Mosaic Virus | 2,000 |
| Tardigrade | 5,700 |
| Deinococcus radiodurans | 10,000 |
History of radiation damage to health
On December 28, 1895 Wilhelm Conrad Röntgen published his study on a new kind of rays ; a month later he reported for the first time in a lecture about the mysterious "X-rays" and X-rayed a hand of the Swiss anatomy professor Rudolf Albert von Kölliker in front of the audience . The exposed image - the picture is still known today - clearly shows the hand bones. This invention sparked great enthusiasm and quickly revolutionized medicine. The New York Sun spoke of a “triumph of science”: Röntgen discovered “a light that penetrates wood and flesh”.
At the end of 1896, specialist journals documented 23 cases of severe radiation damage. Some patients suffered burns from unexpected spreads; others were "literally executed on the treatment table" in the early years of use, wrote James Ewing , a pioneer in radiology . Professor Friedrich Clausen (1864–1900), who demonstrated X-rays in numerous experimental lectures between 1896 and 1900, had burns on his hands as early as 1896. Like many other colleagues, he ignored them. First he lost a few phalanges on his right hand; later his right arm had to be amputated. The amputation came too late; he died six weeks after the operation.
Lead shields were developed, but many doctors found them too expensive or cumbersome, did not protect themselves, and died. "One should not over-dramatize the damage to health," demanded one of the leading radiologists, the Armenian Mihran Kassabian. He feared for progress if the dangers of X-rays are described too vividly. Kassabian himself died of radiation effects in 1910.
Herbert Hawks, a technology-loving student at Columbia University , repeatedly x-rayed his own body in front of an amazed audience in New York department stores. Soon his hair was falling out, his eyes were bloodshot, his chest burned like fire.
In the First World War , "X-rays" finally prevailed: for example, bullets or shrapnel could be localized and broken bones could be fixed. The rays were dosed more carefully; In the twenties, many doctors tried to dose the radiation so that the top layer of skin ( epidermis ) did not turn red.
Other scientists experimented with radiation-emitting substances:
- In February 1896, the French physicist Henri Becquerel discovered that chunks of uranium emit rays that penetrate matter and thus discovered radioactivity .
- The Polish physicist Marie Curie coined the term radioactive in Paris for the property of materials to emit rays. In December 1898, she identified a new element in a uranium ore sample from the Ore Mountains: radium. Without realizing the dangers, she and her husband tried to isolate and measure large amounts of the highly radioactive substance. In 1934 she died almost blind of leukemia at the age of 67. Her daughter was also fatally irradiated.
- In 1903 Ernest Rutherford discovered that there are alpha, beta and gamma radiation and that these penetrate the body to different depths.
- The British inventor Alexander Graham Bell recognized the potential of radiating substances for cancer therapy in 1907. There is no reason why one should not place “a small piece of radium [...] in the middle of a cancer focus”.
Radium was extremely expensive in 1920 at $ 120,000 per gram and was also used for heart problems and impotence. In watch factories, women workers used fine brushes to apply paint containing radium particles to the watch hands so that they glow in the dark. Many workers, also known as " Radium Girls ", had severe radiation damage after a short time.
There were also bizarre applications and ideas, as the US journalist Catherine Caufield documented in her book The Radiant Age of 1989. For example, radium particles were mixed in oil paints to make the picture glow in the dark. Radium water was sold as " eternal sunshine , liquid sunshine". Doramad toothpaste, which contains thorium , was touted as medicinal.
See also
- Radiation biology
- Relative biological effectiveness
- History of radiation damage
- Radiation castration
- Order of magnitude (dose equivalent)
- Health damage from military radar systems
further reading
- L. Wuckel: Irradiation effects in solids. In: M. v. Ardenne, G. Musiol, U. Klemradt (ed.): Effects of physics and their applications. Frankfurt 2005, pp. 294-301.
- Luitgard Mitzel-Landbeck, Ulrich Hagen: Radiation effect on biopolymers. In: Chemistry in Our Time . 10, No. 3, 1976, ISSN 0009-2851 , pp. 65-74.
- PS Geyer: Radiation protection and radiation damage when handling X-rays in veterinary radiology - An examination of the German and English-language literature taking into account the current X-ray ordinance. Dissertation, FU Berlin, 2003.
- Bernd Beek: X-ray-induced cell cycle delay in human leukocytes. In: International Journal of Radiation Biology. 41: 227-230 (1982).
Web links
- Early pictures of radiation damage in: CA Porter: The Surgical Treatment of X-ray Carcinoma and other severe X-ray Lesions, based upon an Analysis of forty-seven Cases . In: The Journal of Medical Research . tape 21 , no. 3 . Boston, USA 1909, p. 357 to 414-417 , PMC 2099032 (free full text).
Individual evidence
- ↑ H.-G. Vogt, H. Schultz: Basics of practical radiation protection. Hanser, 1992, ISBN 3-446-15696-8 .
- ↑ Brockhaus Encyclopedia. 21st edition, 2006.
- ↑ a b M. Nastasi, JW Mayer: Ion Implantation and Synthesis of Materials. Springer, Berlin / Heidelberg 2006, ISBN 3-540-23674-0 .
- ↑ a b A. Dannemann: Investigations into the radiation resistance of polymer materials for use in experiments in high-energy physics. Dissertation, Department of Physics, University of Hamburg , 1996, internal report: DESY F35D-96-06 (PDF; 5.8 MB), accessed on May 25, 2013.
- ↑ W. Busjan: Radiation resistance of scintillating synthetic fibers in high-energy physics: Formation and decay of short-lived absorption centers. Dissertation, Department of Physics, University of Hamburg, 1997.
- ↑ C. Coldewey: Investigations of radiation damage to field effect transistors and to CMOS memory modules. Diploma thesis, Department of Physics at the University of Hamburg, 1991, internal report: DESY F35-91-02 (PDF; 4.5 MB), accessed on June 6, 2013.
- ↑ a b R. Wunstorf: Systematic investigations into the radiation resistance of silicon detectors for use in high-energy physics experiments. Dissertation, Department of Physics, University of Hamburg, 1992, internal report: DESY FH1k-92-01 (PDF; 93.1 MB), accessed on June 9, 2013.
- ^ I. Bohnet , D. Kummerow, K. Wick: Influence of radiation damage on the performance of a lead / scintillator calorimeter investigated with 1-6 GeV electrons . In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment . tape 490 , no. 1-2 , September 1, 2002, ISSN 0168-9002 , pp. 90-100 , doi : 10.1016 / S0168-9002 (02) 01057-4 .
- ↑ E. Fretwurst u. a .: Radiation hardness of silicon detectors for future colliders . In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment . tape 326 , no. 1-2 , March 1, 1993, pp. 357-364 , doi : 10.1016 / 0168-9002 (93) 90377-T .
- ↑ a b c d e Manfred Kriener : One GAU per year doesn't do any harm. - How dangerous is radioactive radiation really? Opinions have differed vigorously on this since Röntgen's discovery. In: The time . No. 16/2011.
- ^ Catherine Caufield: The Brilliant Age . Munich 1994, p. 21.
- ↑ He is also remembered in the honor book of radiologists of all nations , 3rd exp. Edition May 1998, ISBN 3-89412-132-7 .
- ↑ PS Geyer: Radiation protection and radiation damage when dealing with X-rays in veterinary radiology , Department of Veterinary Medicine, FU Berlin, dissertation, 2003, diss.fu-berlin.de Chapter 3 as a PDF file , accessed on June 8, 2013.
- ↑ Kelly's filth . In: Der Spiegel . No. 2 , 1988 ( online documentary article).