That high-energy ionizing radiation harms DNA when it smashes through cells comes as no surprise. Each particle can pack a million times as much energy as a photon of visible light. Yet recent experiments have demonstrated that even remarkably low energy electrons set off by ionizing radiation can break up key molecular components of RNA and DNA. The result has implications for understanding the biological effects of low levels of radiation and for the improvement of radiotherapy treatments.

A particle of high-energy ionizing radiation does not inflict most of its damage by knocking atoms around directly. Instead all along its track it sends electrons flying, like a bowling ball crashing through pins. Each of these "secondary" electrons receives a modest one to 20 electron volts (eV) of energy--comparable to that of a photon in the visible to ultraviolet range. Ionizing radiation knocks loose about 40,000 such electrons for every mega-electron volt of energy that it carries.

This article was originally published with the title Fatal Attachments.

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