A scientifically established connection exists between exposure to certain types of radiation and an increased risk of developing leukemia. This link is influenced by the dose and type of radiation, as well as individual factors. Data confirming this association comes from diverse sources, including medical, occupational, and environmental exposures. While most cases of leukemia have unknown causes, high-energy radiation is a well-identified risk factor.
How Radiation Affects Bone Marrow
Leukemia is a cancer originating in the body’s blood-forming tissues, primarily the bone marrow. Within the bone marrow are hematopoietic stem cells, which are responsible for generating all blood components, including red cells, platelets, and white blood cells. These stem cells are particularly sensitive to ionizing radiation, a form of high-energy radiation that can penetrate the body and interact with cellular structures.
When ionizing radiation passes through a hematopoietic stem cell, it can directly damage the cell’s DNA. This genetic damage can cause mutations, altering the DNA code that instructs the cell on how to function. If these mutations affect genes that regulate cell growth, it can lead to the uncontrolled production of abnormal white blood cells.
The damaged stem cell begins to replicate without restraint, producing vast numbers of non-functional leukemia cells. These cells crowd out healthy blood cells in the bone marrow. This disruption of normal blood production leads to the symptoms and complications associated with the disease. The specific mechanism can differ depending on the type of leukemia that develops.
High-Risk Radiation Sources
The risk of developing leukemia is associated with ionizing radiation, which has enough energy to strip electrons from atoms and damage DNA. This is distinct from non-ionizing radiation, such as that from microwaves and cell phones, which has not been linked to leukemia.
A source of high-dose exposure is medical treatment, such as radiation therapy used to combat cancer. While effective at killing cancer cells, this therapy can also affect healthy tissues like the bone marrow. Certain diagnostic imaging procedures, like computed tomography (CT) scans, also contribute to an individual’s cumulative radiation dose, though the risk from a single X-ray is very low.
Occupational exposure is another source of risk. Individuals in the nuclear industry, radiology, and uranium mining may experience radiation exposure over time, which studies show increases the probability of developing leukemia. Environmental exposure is less common but can occur from nuclear accidents like Chernobyl or from living near nuclear testing sites. Natural sources like radon gas also contribute to background radiation levels.
Risk Factors and Associated Leukemias
The risk of developing leukemia is dependent on the dose received; as the radiation dose increases, so does the risk. This is known as a dose-response relationship. Studies of atomic bomb survivors found that high doses were responsible for nearly all resulting leukemia cases. Even low-dose exposures, however, have been shown to elevate risk.
Another factor is the latency period, or the time between radiation exposure and the onset of leukemia. The risk begins to rise within a few years of exposure, peaking around 5 to 10 years afterward before declining, though it can remain elevated for decades. For some leukemias, the latency period may be longer. Children and adolescents are more susceptible than adults, and exposure before birth carries a greater risk.
Radiation exposure is linked to the development of specific types of leukemia. The highest risks are for Acute Myeloid Leukemia (AML), Acute Lymphoblastic Leukemia (ALL), and Chronic Myeloid Leukemia (CML). In contrast, Chronic Lymphocytic Leukemia (CLL) has not been consistently associated with radiation exposure.