Ionizing radiation, e.g. the "stuff" emitted by radioactive materials, is dangerous to humans since changes to the electron configurations (in the human body) causes the various molecules (in the human body) to change their shape (i.e. break down or form new ones), which can have all sorts of devastating effects..

But why is it any less of an issue if this ionization occurs through more mundane means, like walking over a wool carpet with leather/rubber shoes? Is that ionization any different in quality?

Similarly, why can't the excess/shortage of electrons caused through ionizing radiation not be simply compensated for by "grounding" people, as it occurs with static charges?

..or is perhaps my understanding of why ionizing radiation is an issue for humans a wrong one to begin with?

  • $\begingroup$ Ordinary static or low-frequency electricity doesn't really change the shape of the DNA. It causes currents through the body because the body is a conductor. So in practice, it means that ions of different kinds are moving in different directions in the liquid solution that fills most of our bodies etc. One doesn't have to touch DNA for that - DNA is the much less conductive part of it. With the current, the health hazard is basically the heat produced by it. $\endgroup$ – Luboš Motl Nov 11 '15 at 9:18

Ionizing radiation is radiation that is strong enough so that, when it hits an atom or molecule, will knock off electrons. This happens even if the target object doesn't have freely mobile electrons, which leaves free radicals and broken bonds, both of which are harmful to complex biological processes. There's no selection based on electron binding energy; whatever the radiation hits gets disrupted.

Static electricity, when applied to living tissue, just causes current to flow as in any conductive medium. Due to the presence of salt and other electrolytes, there are electrons available for conduction, and in the electrical field those electrons move to produce a current and drain the static electricity. No individual electron gets energetic enough to break bonds; they just conduct. So, no molecular damage is done.


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