Radiation and Cancer Risk: What You Need to Know

Radiation is an integral part of modern life, ranging from natural sources to medical and industrial applications. However, exposure to radiation, particularly ionizing radiation, may pose significant health risks, with cancer being one of the most notable concerns. This article explores the relationship between radiation and cancer, helping readers better understand the risk factors and effective preventive measures.

1. What Is Radiation?

Radiation is the emission of energy in the form of waves or particles. In medicine and biology, radiation is commonly classified according to its ability to ionize matter.

1.1. Types of Radiation

• Ionizing radiation: Radiation with sufficient energy to remove electrons from atoms or molecules, creating ions. Examples include X-rays, gamma rays, alpha particles, beta particles, and neutrons [1]. Ionizing radiation can damage DNA and other cellular structures, potentially leading to cancer [5].
• Non-ionizing radiation: Radiation with lower energy that is insufficient to ionize matter. Examples include radio waves, microwaves, visible light, infrared radiation, and ultraviolet (UV) radiation [4]. Although UV radiation can cause skin cancer, its mechanism of action differs from that of ionizing radiation.

1.2. Sources of Radiation

Radiation can originate from various sources:

Natural Sources:

• Cosmic radiation: Comes from outer space and interacts with the Earth's atmosphere.
• Radioactivity in rocks and soil: Naturally occurring radioactive elements such as uranium and thorium are present in soil, rocks, water, and air.
• Radon gas: A naturally occurring radioactive gas that is colorless and odorless. It is produced by the decay of uranium in soil and rocks and is a major cause of lung cancer among non-smokers.

Man-Made Sources:

• Medical applications: Medical imaging procedures such as X-rays, CT scans, and PET scans, as well as treatments such as cancer radiotherapy and radiopharmaceuticals used in nuclear medicine.
• Industrial applications: Mining activities, nuclear power plants, and industries that use radioactive materials.
• Consumer products: Certain everyday products may also emit very low levels of radiation.

2. How Does Radiation Cause Cancer?

Ionizing radiation can cause cancer through complex mechanisms at the cellular and molecular levels.

2.1. DNA Damage

The primary effect of ionizing radiation is damage to DNA within the cell nucleus [5]. Radiation can directly disrupt chemical bonds in DNA or indirectly generate free radicals, such as hydroxyl radicals produced from water, which can damage DNA. Types of DNA damage include single-strand breaks, double-strand breaks (DSBs), base damage, and DNA–protein cross-links [3]. Double-strand DNA breaks are considered among the most serious forms of DNA damage because they are more difficult to repair and may result in permanent genetic mutations [3].

2.2. Effects on the Cell Cycle and DNA Repair

When DNA is damaged, cells activate cell-cycle checkpoints to temporarily halt cell division, allowing time for DNA repair. If the damage is successfully repaired, the cell can resume its cycle. However, if the damage is too severe or repaired incorrectly, mutations may occur. These mutations can activate oncogenes or inactivate tumor-suppressor genes, thereby promoting the development of cancer [5].

3. Types of Cancer Associated with Radiation

Types of cancer for which the risk may increase following exposure to ionizing radiation include:

• Leukemia: One of the earliest cancers to develop following radiation exposure. The risk of acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) may increase significantly within 5–10 years after exposure.
• Thyroid cancer: Particularly associated with radiation exposure in children and adolescents, such as exposure to radioactive iodine-131 (I-131) during childhood.
• Breast cancer: The risk of breast cancer may increase in women exposed to radiation, particularly when exposure occurs at a younger age.
• Lung cancer: Radiation exposure, particularly exposure to radon, increases the risk of lung cancer.

4. Factors Affecting Radiation-Related Cancer Risk

The risk of developing cancer following radiation exposure depends not only on the radiation itself but also on several other factors.

4.1. Dose and Exposure Rate

• Dose: Generally, the higher the radiation dose, the greater the cancer risk. This relationship is often described using a linear no-threshold model, meaning that there is no established completely risk-free level of exposure, although the risk at low doses is small.
• Exposure rate: High-dose exposure over a short period (acute exposure) can have different biological effects from the same total dose received over a longer period (chronic exposure). This is partly because the body may have more opportunity to repair DNA damage when exposure occurs gradually.

4.2. Type of Radiation: Ionizing vs. Non-Ionizing

Ionizing radiation can cause direct and indirect DNA damage and therefore has an established potential to cause cancer. Among ionizing radiation types, particles such as alpha particles and neutrons can produce more complex biological damage than X-rays or gamma rays at the same absorbed dose, resulting in higher relative biological effectiveness (RBE) for certain biological effects, including carcinogenesis.

4.3. Age at Exposure

Children and adolescents are generally more sensitive to the carcinogenic effects of radiation than adults. This is partly because their cells divide more rapidly, they have a greater number of developing tissues, and they have a longer remaining lifespan during which radiation-related cancers may develop.

5. Common Sources of Radiation Exposure and Associated Risks

In everyday life, people are exposed to radiation from a variety of natural and man-made sources.

5.1. Medical Radiation: X-rays, CT, and Radiotherapy

Diagnostic imaging procedures such as X-rays and CT scans, as well as treatments such as radiotherapy, use ionizing radiation. Although the diagnostic or therapeutic benefits generally outweigh the associated risks when these procedures are appropriately indicated, repeated or unnecessary exposure may increase cancer risk, particularly in children.

• CT scans: CT is a major contributor to population medical radiation exposure, with effective doses varying widely depending on the type and protocol of the examination.
• Radiotherapy: Radiotherapy uses high doses of radiation to destroy cancer cells but may also increase the risk of secondary tumors in irradiated areas or nearby tissues many years after treatment.

5.2. Occupational Radiation Exposure

People working in environments with higher radiation exposure, such as nuclear power plants, radiation research facilities, or healthcare settings involving X-ray procedures and radiotherapy, may be exposed to occupational radiation. Strict protective measures and dose monitoring are implemented to minimize these risks.

5.3. Environmental Radiation

• Radon gas: Radon is a major cause of lung cancer among non-smokers. It can accumulate indoors, particularly in enclosed buildings and areas where naturally occurring uranium levels in the soil are high.
• Living near nuclear power plants: Studies have assessed cancer risks among populations living near nuclear facilities. Although modern nuclear power plants operate under strict safety procedures, some studies have suggested possible associations, particularly with childhood leukemia; however, findings have been inconsistent and remain an area of ongoing research.

5.4. Limiting Unnecessary Medical Radiation Exposure

• Perform imaging only when necessary: Ensure that imaging examinations involving radiation, such as X-rays and CT scans, are performed when there is a clear medical indication and when no equally effective non-ionizing alternative is available, such as ultrasound or MRI.
• Optimize radiation dose: Physicians and radiologic technologists should use the lowest radiation dose reasonably necessary to obtain diagnostic-quality images.
• Use non-ionizing alternatives when appropriate: For pregnant women and children, non-ionizing imaging methods should be preferred whenever clinically appropriate.

6. When Should You See a Doctor?

Individuals should consult a doctor if they have concerns about radiation exposure or experience persistent, unexplained symptoms such as:

• Unexplained fatigue.
• Sudden or unexplained weight loss.
• Persistent fever.
• Persistent pain.
• Swollen lymph nodes.
• New lumps or unusual changes in the skin.

In particular, individuals with a history of significant radiation exposure, such as previous radiotherapy or occupational radiation exposure, should inform their doctor if any of these signs or symptoms occur so that appropriate medical assessment and screening can be considered.

7. References

• [1] National Research Council (US) Committee on the Biological Effects of Ionizing Radiation (BEIR V). (1990). Health Effects of Exposure to Low Levels of Ionizing Radiation: BEIR V. National Academies Press (US). Accessed December 15, 2025.
• [2] Nakamura, N. (2022). Mechanisms of Radiation Carcinogenesis: What Is Really Induced? Radiation Protection Dosimetry, 198(13–15), 1090–1097. Accessed December 15, 2025.
• [3] Najafi, M., Fardid, R., Hadadi, G., & Fardid, M. (2014). The Mechanisms of Radiation-Induced Bystander Effect. Journal of Biomedical Physics & Engineering, 4(4), 163–172. Accessed December 15, 2025.
• [4] Imaoka, T. (2025). Trans-Scale Insights into Variability in Radiation Cancer Risk Across Tissues, Individuals, and Species. Biology, 14(8), 1025. Accessed December 15, 2025.
• [5] Committee on the Analysis of Cancer Risks in Populations Near Nuclear Facilities—Phase I; Nuclear and Radiation Studies Board; Division on Earth and Life Studies; National Research Council. (2012). Radiation as a Carcinogen. National Academies Press (US). Accessed December 15, 2025.
• [6] Little, J. B. (2003). Principal Cellular and Tissue Effects of Radiation. In D. W. Kufe, R. E. Pollock, R. R. Weichselbaum, et al. (Eds.), Holland-Frei Cancer Medicine (6th ed.). BC Decker. Accessed December 15, 2025.
• [7] Dracham, C. B., Shankar, A., & Madan, R. (2018). Radiation Induced Secondary Malignancies: A Review Article. Radiation Oncology Journal, 36(2), 85–94. Accessed December 15, 2025.

The information provided above is for reference purposes only and does not constitute a medical recommendation. Please consult a doctor for detailed advice.