Why are children more sensitive to radiation than adults?

• A. Their mitotic activity is higher
• B. Their bodies are smaller
• C. Their body parts are thinner
• D. They are not as capable of cooperation

Answer: (A)

Radiosensitivity is highest in tissues that have rapid cell division and less mature differentiation. In children, growth means many cells are actively dividing, so a larger fraction of cells are in mitosis when radiation occurs. If DNA is damaged during those divisions, it’s more likely to lead to cell death or mutations, increasing the risk of tissue injury and later effects like cancer. Add to that the longer remaining lifespan of a child, which gives more time for late effects to develop. This makes higher mitotic activity the best explanation for why children are more sensitive to radiation.

The other factors—smaller body size, thinner body parts, or a child’s ability to cooperate—affect how much dose is delivered or how well imaging can be performed, but they don’t explain the intrinsic, biological vulnerability that comes from high cellular proliferation.