Which type of blood cells are the first to become affected after exposure to radiation?

White blood cells are the first type of blood cells to become affected after exposure to radiation because they are crucial components of the immune system and are rapidly dividing cells. Radiation primarily damages cells by creating free radicals and causing breaks in DNA strands, which is especially impactful on tissues with high turnover rates, such as those involved in the production of white blood cells in the bone marrow.

The bone marrow generates various types of white blood cells essential for immune responses. Because these cells are constantly being produced and replenished, they are more susceptible to the immediate harmful effects of radiation compared to other types of cells that might have slower turnover rates. When exposed to radiation, the count of white blood cells can decrease rapidly, which can lead to compromised immune function and increased vulnerability to infections.

While red blood cells, platelets, and plasma cells are also affected by radiation exposure, they usually show changes after white blood cells due to their different production rates and recovery mechanisms in the body. Therefore, the correct answer is that white blood cells are the first to be impacted.