Strontium-90 is a radioactive isotope that behaves chemically very much like calcium, which means it tends to accumulate in bones and bone marrow once it enters the body. This is because the body mistakes strontium-90 for calcium and incorporates it into the bone structure during normal bone formation and remodeling processes. When strontium-90 is ingested, usually through contaminated food or water, about 70 to 80 percent is excreted, but the remainder is deposited primarily in bones and bone marrow, where it can remain for many years due to its long biological half-life.
The presence of strontium-90 in bones is particularly concerning because it emits beta radiation, which can damage the cells in and around the bone tissue. This radiation exposure can lead to several harmful effects. One major effect is the increased risk of bone cancer. Since strontium-90 is lodged in the bone matrix, its radioactive decay continuously irradiates the bone cells, potentially causing mutations that lead to cancerous growths. Additionally, the bone marrow, which is responsible for producing blood cells, is also exposed to this radiation. This exposure can disrupt normal blood cell production and increase the risk of leukemia, a cancer of the blood-forming tissues.
The bone marrow is a critical site for the production of red blood cells, white blood cells, and platelets. Radiation from strontium-90 can damage the stem cells in the marrow, impairing their ability to produce these vital cells. This can lead to conditions such as anemia (due to reduced red blood cells), increased susceptibility to infections (due to reduced white blood cells), and bleeding problems (due to reduced platelets). The damage to bone marrow cells can be long-lasting because strontium-90 has a biological half-life in the body estimated to be around 18 years on average, meaning it can remain active and harmful for decades.
The biological half-life of strontium-90 varies widely depending on factors such as age, sex, and individual metabolism, but its long retention in bones means that the radiation dose to bone and marrow accumulates over time. Children and young individuals are particularly vulnerable because their bones are growing and remodeling more rapidly, leading to greater incorporation of strontium-90 and potentially more severe effects.
At the cellular level, the radiation from strontium-90 causes ionization events that produce free radicals and reactive ions. These reactive molecules can damage DNA and other critical molecules within bone and marrow cells. Over time, this damage can lead to mutations, cell death, or malfunction, contributing to the development of cancers and other bone marrow disorders.
Moreover, strontium-90’s similarity to calcium means it can interfere with normal bone metabolism. Calcium plays a key role in bone strength and remodeling, and strontium-90’s presence can disrupt these processes, potentially weakening bones or altering their normal growth patterns. This disruption can exacerbate the risk of fractures and other skeletal problems.
In summary, strontium-90’s effect on bones and marrow is primarily due to its radioactive nature combined with its chemical mimicry of calcium. It accumulates in bones, irradiates bone cells and marrow over long periods, increases the risk of bone cancer and leukemia, damages blood cell production, and disrupts normal bone metabolism. These effects make strontium-90 a particularly dangerous radionuclide when introduced into the human body.