From natural sources, like minerals in the Earth, cosmic rays, and the sun, to man-made sources, such as medical equipment, electrical power lines, and radio waves from cell phones and Wi-Fi, “We are exposed to radiation in our everyday life,” according to the International Atomic Energy Agency.
You might be wondering, “If radiation is all around us, why doesn’t everyone have cancer?” Good question. This article answers that question and explains the difference between ionizing and non-ionizing radiation, how radiation causes cancer, and the factors that may lead to carcinogenic outcomes.
Types of Radiation
Radiation is energy released in the form of particles or electromagnetic waves. It has two main categories: ionizing and non-ionizing.
What Is Ionizing Radiation, and Why Is It Harmful?
Ionizing radiation contains so much energy that it can knock out electrons from atoms. This process (ionization) forms ions, which disrupt chemical bonds and damage biological tissue.
Natural sources of ionizing radiation include but are not limited to:
- Cosmic rays: Radiation from outer space that reaches the Earth’s surface.
- Terrestrial radiation: Radiation from naturally occurring radioactive elements in soil and rocks.
- Radon: A radioactive gas that emanates from soil and rocks and accumulates in homes.
- Radioactive elements in the body: Small amounts of naturally occurring radioactive elements are present in the human body.
Human-made sources of ionizing radiation include:
- Medical imaging: X-ray, computed tomography (CT), and positron emission tomography (PET) scans use radiation to diagnose conditions.
- Radiation therapy: Oncologists use high-energy radiation to kill cancer.
- Nuclear power plants: Mishaps at nuclear power plants can release high amounts of ionizing radiation.
- Atomic weapons: The production, testing, and use of atomic weapons can result in high radiation levels.
Types of ionizing radiation include:
- X-rays and gamma rays: Bundles of energy without mass, but with very high energy.
- Alpha particles and beta particles: Energetic charged particles.
Ionizing radiation poses a carcinogenic risk due to its ability to damage DNA or produce reactive oxygen species that lead to indirect DNA damage.
What Is Non-Ionizing Radiation?
Non-ionizing radiation is a low-energy type of electromagnetic radiation. Unlike ionizing radiation, it cannot remove electrons from atoms or molecules.
Sources of non-ionizing radiation include:
- Radio waves
- Microwaves
- Infrared radiation
- Visible light
- Ultraviolet (UV) radiation (lower-energy UV)
While non-ionizing radiation lacks the energy required to ionize atoms in DNA, high exposure to specific frequencies, such as ultraviolet B (UVB), may increase the risk of skin cancer.
What Does “Ionize” Mean? A Simpler Explanation
Ionization, or to ionize, means to remove or add an electron to an atom or molecule, which turns it into an ionized atom (a charged particle). It’s dangerous because:
- Ionized atoms can break DNA strands, trigger mutations, and disrupt cell functions.
- These mutations can trigger uncontrolled cell growth, which is the basis of cancer.
As for non-ionizing radiation, it contains insufficient energy to ionize atoms. However, prolonged and intense exposure to some types can still cause other forms of DNA damage.
How Ionizing Radiation Damages Cells
The health effects of ionizing radiation vary based on how it interacts with tissues.
- Direct DNA damage: Radiation can strike the DNA molecule itself, breaking its strands or altering its chemical structure.
- Indirect DNA damage: Radiation can ionize water molecules in cells, producing free radicals. These unstable molecules attack DNA, proteins, and cell membranes.
Both mechanisms disrupt normal cellular processes. Cells may repair some of the damage, but errors during repair can lead to permanent genetic mutations.
In other words (and to finally answer that burning question), not everyone gets cancer despite constant exposure to radiation because the human body has repair mechanisms and a process called apoptosis that eliminates most damaged cells before they become cancerous. Also, not all radiation causes cancer; only excessive (prolonged and/or intense) exposure to ionizing radiation increases one’s risk.
How Cancer Develops After Radiation Exposure
Radiation-induced cancer develops through the following steps:
1. Initiation
Initiation begins when radiation damages the DNA of a single cell. If repair processes fail, a permanent mutation may become fixed in the genome.
2. Promotion
In the promotion phase, the initiated cell (permanently mutated cell) undergoes repeated cycles of division. Radiation may also act as a promoter by affecting surrounding tissues. It increases inflammation and cellular proliferation.
3. Progression
The progression phase involves additional mutations that enhance cell survival, angiogenesis, and resistance to apoptosis. These changes support tumor development and metastasis.
Types of Cancer Linked to Radiation Exposure
High-dose, whole-body external exposure is more likely to cause the following radiation-associated cancers:
- Leukemia, especially acute myeloid leukemia
- Thyroid cancer
- Breast cancer
- Lung cancer
- Skin cancer
- Soft tissue sarcoma
Factors Affecting Cancer Risk From Radiation
As mentioned, not every radiation exposure leads to cancer. Several factors determine one’s risk or susceptibility:
- Dosage: The higher the dose, the more chances of inflicting damage that overwhelms repair systems.
- Type of radiation: Alpha particles, beta particles, gamma rays, and X-rays affect tissues differently. Alpha particles cause intense local damage but travel short distances, while gamma rays penetrate more deeply.
- Rate of exposure: A high dose in a short period causes more severe damage than the same dose spread over time.
- Age at exposure: Children and adolescents are more sensitive to radiation because their cells divide more rapidly.
- Body tissues exposed: Certain organs, such as the thyroid gland, breast tissue, and bone marrow, are especially sensitive to radiation-induced cancer.
Historical and Medical Evidence
Historical events and medical studies have documented the cancer-causing effects of radiation:
1. Atomic Bomb Survivors
Survivors from Hiroshima and Nagasaki revealed increased rates of leukemia and solid tumors.
2. Nuclear Accidents
The Chernobyl and Fukushima disasters exposed nearby populations to radioactive fallout. Children, in particular, who absorbed radioactive iodine through food and air experienced a rise in thyroid cancer diagnoses.
3. Secondary Cancers After Radiation Therapy
Cancer patients treated with radiation therapy have a measurable increase in later malignancies, particularly leukemia within 5 to 10 years of exposure, and sarcomas, breast cancer, and lung cancer appearing after 10 or more years.
Why Radiation Treats and Causes Cancer
While high doses of ionizing radiation damage the DNA of cancer cells so severely that they die, radiation also injures healthy tissues and raises the risk of secondary cancers years later. After surviving a primary malignancy, studies show that between 17% and 19% of all patients develop a second malignancy.
The Need for Less Harmful Cancer Treatments
Since radiation damages healthy tissue and induces secondary cancers, oncology researchers and clinicians continue to examine treatment modalities that reduce collateral injury. Two such methods include:
1. Immunotherapy
Immunotherapy employs the body’s immune system to recognize and attack cancer cells. Approaches include:
- Checkpoint inhibitors that remove inhibitory signals from immune cells.
- Cytokine therapies that enhance immune activation.
- Cell-based treatments such as CAR-T cell therapy.
These treatments minimize exposure to surrounding healthy tissues and do not involve ionizing radiation.
2. Targeted Therapies
Targeted therapies address molecular abnormalities specific to cancer cells. Agents used in this method include:
- Monoclonal antibodies
- Kinase inhibitors
- Hormone receptor blockers
Because these therapies target specific cellular pathways, they lower the body-wide toxicity that conventional treatments like radiation cause.
Immunotherapy and targeted therapy give cancer patients treatment options that attack tumors while limiting harm to surrounding tissues. These methods strengthen the body’s own defenses or block cancer at its genetic drivers rather than harming large areas of healthy cells.
Patients who want alternatives to conventional methods can speak with the team at New Hope Unlimited to learn how immunotherapy and targeted options may improve their prognoses.
