Which particles only cause damage when ingested?

• A. Alpha
• B. Beta
• C. Gamma
• D. X-ray

Answer: (A)

Alpha radiation deposits a lot of energy over a very short distance, so it causes intense damage to cells, but only if the radiation source is inside the body. External alpha exposure is minimal because alpha particles cannot penetrate skin or clothing. When alpha-emitting material is inhaled or ingested, it irradiates surrounding tissues directly, leading to significant localized injury. Beta particles, gamma rays, and X-rays have greater penetration and can cause damage from outside the body as well as inside, so they aren’t limited to ingestion-based harm. That internal-only risk profile is what makes alpha the best answer.