What hazard is associated with alpha radiation?

Alpha radiation presents a significant hazard primarily when alpha particles are ingested or inhaled. This is due to the nature of alpha particles, which consist of two protons and two neutrons. Although they have a low penetration power and can be stopped by a sheet of paper or even the outer layer of skin, their high mass and charge make them extremely damaging to biological tissues if they interact with living cells inside the body. When alpha-emitting materials are ingested or enter the lungs, they can cause serious health risks, including cellular damage and an increased risk of cancer, since they can deposit substantial energy over a very short distance within the body's tissues.

The other options do not accurately reflect the characteristics of alpha radiation. While it's true that alpha radiation is mostly harmless externally due to its inability to penetrate the skin, the focus on external exposure overlooks the serious internal risks. Similarly, alpha particles indeed have low penetration power, which contradicts any notion of strong penetration capabilities. Furthermore, claiming that they travel easily through air fails to recognize that alpha particles quickly lose energy and become ineffective even over short distances.