• Question: how are ionising radiation and skin cancer linked?

    Asked by anon-244767 on 30 Apr 2020.
    • Photo: Joel Goldstein

      Joel Goldstein answered on 30 Apr 2020:

      Ionising radiation consists of subatomic particles (typically electrons, muons, photons or atomic nuclei) travelling very fast – in some cases close to the speed of light. They can penetrate some distance through most materials, but may interact with the material they are passing through by ionising it (hence the name!) You can think of these subatomic particles as bullets, breaking apart molecules of the material they are passing through.

      In the case of living tissue, this ionisation can have lots of effects, disrupting the normal operation of cells, damaging and possibly killing them. Particularly dangerous is when the incident particle damages the genetic material (i.e. the DNA) in the nucleus of the cells – there are natural mechanisms that try to repair the damage, but sometimes these do not work and the result can be a mutation in the cells’ DNA. Some of these mutations don’t matter, some could cause evolution, but some can turn the cell into a cancer cell that then starts dividing uncontrollably.

      In the specific case you mention, ultra-violet light (from the sun) is a form of ionising radiation, but does not penetrate very far so most of the energy is deposited in the skin – this is why it predominantly causes skin cancer.

    • Photo: Susan Cartwright

      Susan Cartwright answered on 30 Apr 2020:

      Ionising radiation is so called because it can ionise atoms – i.e. knock electrons off. This can disrupt the bonds holding a molecule together. In the case of large molecules this probably isn’t enough to break them apart completely, but may affect their shae and their chemistry. Charged particles such as those emitted in radioactive decay (alpha particles and electrons) are ionising radiation, and so are very high-energy photons (X rays and gamma rays). Ordinary visibale light is non-ionising, as its photons have too little energy to ionise atoms.

      In the case of cancer, what happens is that the ionising radiation damages the cell’s DNA. Cells do have mechanisms to repair DNA damage, but if the dose of ionising radiation is too great then these are overwhelmed and the samage is not repaired. This may simply kill the cell, but in some cases what it does is destroy the signalling mechanisms that control the cell’s reproduction – that is, the circumstances in which it divides to form two cells. If the regualtry mechanism is switched off by the DNA damage, the cell multiplies out of control, which is what causes cancer.

      Ironically, ionising radiation can also be used to treat cancer (radiotherapy). This is done by targeting the cancer with a dose of radiation that is high enough that the cells are not merely damaged but killed outright.

    • Photo: anon

      anon answered on 30 Apr 2020:

      “Ionising” part means that molecules get charged when the radiation knocks out electrons or even ions from them. A charged molecule is much more reactive than a neutral one, so this triggers some chemistry that is not supposed to be there, leading to errors in the cell machinery. These errors can be small and non-significant, or they can be critical and make the cell defective or worse, mutated (if the error is in the cell division mechanism, DNA or associated machinery). Mutated cells can become or produce cancer cells – there is an excellent kurzgesagt video on this.
      There are mutations occurring naturally as well, but as radiation produces “extra” mutations, the probability of cancer cells appearing gets higher.

    • Photo: James Smallcombe

      James Smallcombe answered on 1 May 2020: last edited 1 May 2020 8:28 am

      Ionising radiation comes in lots of different types but they can all cause ionisation of the atoms in our bodies. This usually doesn’t do any harm, but can occasionally break DNA in a cell which could lead to cancer. Our skin does a fantastic job of protecting us from lower-energy radiation as much of it is stopped in the outer layers of dead cells. However some forms of radiation can penetrate this and have a small chance of causing cancer. Ultraviolet (UV) light in particular is associated with skin cancer, as it is part of sun-light we can be exposed to a lot of UV making those small chances of cancer bigger. But UV light cant reach further into the body so doesn’t cause other cancers directly.

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