Origin of water’s DNA-damaging slow electrons discovered

Excited water molecules can rid themselves of their extra energy by producing slow electrons, the kind that can damage DNA.

When molecules collide with high-energy projectiles like x-rays or γ-radiation, it can knock out one of their core electrons. To return to an energetically more comfortable state, one of the molecule’s higher energy electrons jumps in to fill the gap. The energy released during this process can be transferred to yet another electron that is then ejected, creating an ion.