Which type of radiation has little penetrating power and poses health risks primarily through ingestion or inhalation?

Alpha particles are composed of two protons and two neutrons, essentially making them helium nuclei. This structure gives them a relatively large mass and a positive charge, resulting in them having low penetrating power. They can be easily stopped by a sheet of paper or even the outer layer of human skin. However, the health risks associated with alpha particles primarily arise when they are ingested or inhaled. Once inside the body, alpha emitters can damage the cells and tissues near the site of decay due to their high ionization potential. This ionization can lead to significant biological harm, including potential carcinogenic effects.

In contrast, other forms of radiation, such as X-rays and gamma rays, have much more penetrating power and can pass through the body, which is why they pose different types of health risks and are evaluated according to their exposure and protection standards. Beta particles, while more penetrating than alpha particles, still do not pose as significant risks via ingestion or inhalation compared to alpha particles.