Which hazard arises when ionizing radiation interacts with living tissue?

When ionizing radiation interacts with living tissue, it primarily causes the ionization of atoms. This process is the fundamental mechanism by which ionizing radiation inflicts biological damage. Ionization occurs when radiation, such as X-rays or gamma rays, carries enough energy to eject electrons from atoms in biological tissues, leading to the formation of charged particles known as ions.

The production of ions can disrupt molecular bonds and create free radicals, which are highly reactive species that can further damage cellular structures, including DNA. This molecular damage can lead to a range of biological effects, from cell death to mutations. Mutations in DNA can lead to long-term consequences, such as the development of cancers, which is why understanding the ionization effect is crucial in radiation protection.

While the other options may seem relevant to some extent, they do not directly represent the primary hazard posed by ionizing radiation. Melting and heating of tissues typically refer to thermal effects, which are not the main concern with ionizing radiation. Development of tumors is a potential long-term effect, but it stems from the initial ionization and subsequent cellular damage. Therefore, ionization of atoms is the foundational hazard that leads to these further biological consequences.