What is the term for the type of molecular change induced directly by radiation?

The term that refers to the type of molecular change induced directly by radiation is the "direct effect." This concept involves the immediate alteration of molecular structures as a result of radiation energy directly imparted to the molecules themselves. When ionizing radiation interacts with the biological tissue, it can directly ionize atoms and disrupt molecular bonds, leading to changes in the chemical structure of molecules such as DNA, proteins, and other vital cellular components.

In the context of radiobiology, understanding the direct effect is essential because it highlights how radiation can initiate biological damage and potentially lead to mutations, cell death, or other adverse biological effects. This is key to assessing how radiation exposure can impact human health and has significant implications for radiation safety protocols.