Which type of radioactive particles presents the greatest risk once inside the body?

Alpha particles present the greatest risk once inside the body due to their unique properties. When alpha emitters are ingested or inhaled, these heavy, positively charged particles can cause significant damage to biological tissues and cells. This is primarily because alpha particles have a high mass and can deliver a large amount of energy over a very short range, typically just a few micrometers.

Inside the body, alpha particles can ionize nearby atoms and molecules, leading to potential mutations or damage to DNA and cellular structures. Because their energy is deposited in a concentrated area, even a small number of alpha particles can lead to harmful effects, making them particularly dangerous compared to other types of radiation.

In contrast, gamma rays are highly penetrating and can pass through the body without imparting much energy to it, making their risk lower when compared to alpha particles, which lack this penetrating power. Beta particles, while also damaging, have a different energy deposition profile and generally cause less localized damage than alpha particles. The term "Delta," however, is not commonly associated with a specific type of radioactive particle in this context, which further indicates that alpha particles are indeed the most hazardous when internalized into biological systems.