Hematopoietic Syndrome ARS is primarily associated with exposure to which dose?

• A. 0.5 Gy
• B. 1 Gy
• C. 5 Gy
• D. 20 Gy

Answer: (B)

Hematopoietic ARS shows up when the bone marrow is chiefly affected, so the dose at which this syndrome dominates is the key idea. About 1 Gy of whole-body exposure is the level where bone marrow suppression becomes the primary and most characteristic effect. At this dose, enough marrow cells are damaged to markedly reduce white blood cells and platelets, leading to infection risk and bleeding and driving the clinical picture of hematopoietic syndrome. As the dose increases, other syndromes become more prominent: around several Gy the gastrointestinal tract can be affected, and at very high doses (roughly 20 Gy or more) the nervous system symptoms dominate. Very low doses (like 0.5 Gy) typically don’t produce the full hematopoietic syndrome. So 1 Gy best aligns with hematopoietic ARS being the primary syndrome.