Is there a more complex process happening at the celular level that means you need the levels of radiation to be higher than a certain amount before there is any risk of cancer?
Or is it as simple as each ray of gamma radiation that penertrates the skin could give you cancer and you “role the dice” with each one?
In: Physics
At a basic level, yes, each individual photon has a chance of causing a mutation that has a chance of leading to a cancer.
I believe there is *some* evidence that very low levels of radiation actually reduce cancer rates, with the possibility that they encourage the body to mobilise a response to the damage.
This is not very well established though, and the mechanism is speculative. The evidence is based on population studies so there could be other factors involved.
It is assumed to be the case. The only real useful data on this comes from the survivors of the atomic bombs in Japan. This data shows a linear relationship between dose and cancer. Basically, more radiation = more cancer risk. But the data is only valid for high doses (>100 mSv).
The question is if this relationship is valid at low doses. Like the low doses you get from medical x-rays etc. Like I said, it is assumed to be the case, since there is no contrary evidence, and to “play it safe”.
In vitro cell studies have been performed (shoot radiation at cells in a petri dish), and some studies see that cells appear to be extra *sensitive* at low doses, and some studies see that cells appear to be extra *resistant* at low doses. So it is complicated and remains unknown!
[This graph sums it up nicely.](https://www.researchgate.net/profile/Mariateresa_Mancuso/publication/221902556/figure/fig3/AS:393912628858886@1470927497480/Fig-3-Linear-Non-Threshold-LNT-model-and-uncertainties-in-extrapolation-of.png)
At high doses there is data, which shows a linear relationship. At low doses, it is not known whether the trend is supralinear or sublinear, or anything else. It is also not known what happens at *really high* doses (the trend probably decreases, since you end up killing everything instead of inducing mutations).
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TLDR:
At high doses, more radiation = higher cancer risk.
At low doses, it is not known, and appears to be much more complicated.
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