There are plenty of lists of sources of general background radiation, but can anyone reduce that list to the major contributing sources purely for background gamma radiation (specifically low energy, x-ray-ish level)? I'm more interested in measurements in Curies, rather than Sieverts if possible.

Thank you

  • $\begingroup$ Gamma rays are, practically by definition, extremely high energy, high frequency electromagnetic waves. Therefore, to ask about "low energy, x-ray-ish" gamma rays is like asking for square circles. $\endgroup$
    – Sean
    Commented Mar 27, 2015 at 0:12
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    $\begingroup$ If he's simply making the distinction between photons (represented with a $\gamma$ at all energies in particle-physics) and massive particle radiation, the meaning is clear. $\endgroup$ Commented Mar 27, 2015 at 0:16
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    $\begingroup$ On the other hand, buzsh does have a problem with his units request. Curies is not a dose. It's just a count of events per unit time (and the SI unit of activity is the Becquerel with $1 \,\mathrm{Ci} \approx 3.7 \times 10^{10} \,\mathrm{Bq}$). Sieverts is a measure of biological damage from radiation. They are not at all the same thing. There is no general conversion for $\mathrm{Ci}$ to $\mathrm{Sv}$, and to define one for a particular case requires you to specify radiation type, radiation energy and absorption profile. None of which we have. $\endgroup$ Commented Mar 27, 2015 at 0:22
  • $\begingroup$ @Sean: There is no clear cut-off between X-ray and $\gamma$ ray in the EM spectrum, just "somewhere" in the upper MeV range. So saying "low energy, x-ray-ish$ isn't really much of a problem (though it'd be more clear with a statement like with $E\in[10,400]\,\rm MeV$) $\endgroup$
    – Kyle Kanos
    Commented Mar 27, 2015 at 0:41
  • $\begingroup$ Sorry, for some reason I was thinking radio wave instead of x ray when I read the question. $\endgroup$
    – Sean
    Commented Mar 27, 2015 at 1:15

1 Answer 1


It is, perhaps easier to catalog the non-photon sources and leave the addition and unit conversion to you.

  • The cosmic background is almost entirely muons.

  • If you spend times in building with non-trivial radon level, that does it largely alpha.

  • Most (but not all) of the natural radiation background is gamma, but it runs a wide range of energies for a few $\mathrm{keV}$ up to more than $1 \,\mathrm{MeV}$.


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