It is a matter of confusing terminology , at the present times when so much differentiation has happened in physics related scientific disciplines.
Radiation was a general terminology assigned to transfer of energy radially, to start with with waves: acoustic waves, waves in water.
Then came Maxwell's equations and the discovery of electromagnetic waves, which emitted energy in waves from a point source radially. ( in the beginning they thought ether existed on which the waves transferred the energy, but that is another story)
Then came the experimental discovery of nuclear energy, which emits energy radially from point sources, and is invisible to the eye . It was called radiation and the elements emitting it were called radioactive. This is where the split happens, between the strict meaning in physics of radiative transfer of energy through waves, and the nuclear community vocabulary: radiation is any ( note not particularly wave) form of radially emitted energy from a source/nucleus.
This last meaning has dominated the vocabulary of nuclear related disciplines, like health physics, and certainly the news. Certainly it is not wrong, it is just a double use of the term.
In nuclear physics you can call radiation gamma rays and be true to the wave definition, because a gamma is an electromagnetic wave that is emitted radially from the source. Alpha (helium nuclei), beta+/- ( positrons/electrons) , higher nuclear fragments from heavy nuclei breakups will also be called radiation for health physics purposes too, with the second meaning of the term.
Electromagnetic radiation has a spectrum of frequencies, beginning from infrared to gamma ray energies. At low energy, i.e. in the infrared regime, you know electromagnetic radiation as radio waves, microwaves or "heat radiation". At intermediate energies it makes up the visible light. At even higher energies, it can be ionizing, if the energy of the radiation is higher than the energy with which the electrons are bound in an atom. These range from X-Rays to gamma rays.
I would agree with the general conclusions regarding soft x-rays. I have measured the attenuation of x-rays in every day materials at energies below 20 Kev and to a first approximation can be described by :-
E½ = K t^1/3.25 where t is the thickness in cm. E½ the energy at which the intensity is reduction to ½ . K is the coefficient of the material.
For example a sheet of solid styrene K = 17.77 and E½ = 8.7 Kev for 1 mm thick sample. While the exact K value will depend some what on your particular specimen it might be interesting to compare the attenuation using other materials.
Cling film 13.3, Black card 18.4, Writing paper 23.5, Black polythene 14.7,
Clear polythene 13.3, Mica 51, PCB Fibre glass 40, Beryllium 11.23 , Aluminium 46.6,
Best Answer
Indeed, it's likely that the rice came from Japan, and if it did, it's pretty likely it came from the Fukushima region which is famous across Japan and beyond for its rice - and other products. However, it could have been harvested before the tsunami. But as discussed here,
the measurements indicate that the contamination of all these products has been minimal even when it was found, and you would need to eat many kilograms of this rice - or something else - to approach the radioactive dose that you obtain from one healthy banana (produced outside Japan).
Of course, I can't guarantee that one particular package of rice couldn't contain an amount of radioactivity that is higher by three orders of magnitude - but it's just unlikely. Don't get me wrong: if I were you, I could react in the same sensitive way. But from my perspective right now, you will shorten your life much more visibly by the worries than by the actual radioactivity.
The radioactive content in that food is almost certainly pretty much indistinguishable from the natural levels. No one could have harvested rice and other plants in the truly contaminated areas around the power plant after the nuclear hassle (and only then it mattered) - because they had been evacuated. And the contamination in the more distant places is just small and when one computes what can get inside rice and survive for long enough time, it's negligible.
Moreover, when you eat radioactive isotopes, it's actually not the most permanent source of radioactivity and cancer risk. This stuff mostly gets out of your body within two months or so. Breathing plutonium is more risky. See this summary of the health impact of the basic radioactive isotopes:
Again, there is no reason to think that by eating the rice, you have been overexposed to these isotopes.