What is the primary hazard of alpha radiation in terms of body exposure?

The primary hazard of alpha radiation in terms of body exposure is that it produces significant ionisation internally. Alpha particles have a high mass and a positive charge, which means they can cause substantial ionisation when they interact with matter, particularly biological tissues.

When alpha-emitting substances are ingested or inhaled, they can deliver a large amount of energy over a very short distance within the body, resulting in ionisation of the cells and potentially causing severe biological damage, including cancer. Although alpha particles cannot penetrate the outer layer of human skin and typically do not pose a danger from external exposure, their risk increases dramatically when they enter the body.

Understanding the behavior of alpha particles clarifies the misconception that they are harmless due to their inability to penetrate the skin. In contrast to external exposure, internal exposure presents a high level of harm, making the risk associated with alpha radiation notable.