Key Takeaways
- There are two types of radiation, ionizing (which can remove an ion from an atom) and non-ionizing (which is too weak for this). Both pose risks, especially at high doses.
- Ionizing radiation has been shown conclusively to increase the risk of breast cancer, thyroid cancer, lung cancer, brain cancer, leukemia, and overall cancer risk.
- Other than UV exposure, non-ionizing radiation has not been conclusively tied to cancer, but studies into the effects of non-UV sources of non-ionizing radiation–including radiation from cell phones–are ongoing.
- Many common medical tests and treatments involve ionizing radiation, though usually at low doses. Your doctor will generally weigh the risks and benefits of these tests or treatments in deciding to recommend them. If you’re concerned about exposure, you can sometimes request a non-radiative alternative (such as MRI or ultrasound imaging).
What is the difference between ionizing and non-ionizing radiation?
You may have heard that radiation exposure can cause health problems, but it may surprise you to learn how prevalent radiation really is. Everyone on earth is exposed to radiation on a daily basis, primarily from sources outside of our control[1], such as radon in the air, cosmic radiation (from space), and even radiation that naturally occurs in the human body.
When we talk about radiation exposure, there are two main types of radiation to consider:
- Ionizing radiation is a higher-energy form of radiation, and can remove ions from atoms or molecules it comes into contact with.
- Non-ionizing radiation does not have enough energy to remove ions, but it can heat substances, including body tissues. Microwaves are a common type of non-ionizing radiation.
Ionizing radiation: exposure paths
People are exposed to ionizing radiation via both natural and manmade sources. Natural sources of exposure–i.e., those that can’t be completely controlled for–include[2]:
- Radon in the air formed by the breakdown of uranium in soil, water, or building materials (learn more about the risks of radon here)
- Radioactive elements in the human body (this is an extremely small source of exposure)
- Cosmic radiation[3]
Your exposure to radon and cosmic radiation can vary significantly. Radon gas forms naturally, and can become trapped in buildings, concentrating your exposure. Testing your home or workplace is the only way to know your exposure level [4]. Cosmic radiation comes from space, but most of it is absorbed by the earth’s atmosphere. However, living at higher elevations, or jobs that require significant travel–particularly long-haul flights and flights over the poles–can increase your exposure. This is due to the fact that less of the radiation is dispersed by the atmosphere at higher elevations.
Man-made sources of ionizing radiation account for an estimated 48% of the average individual’s exposure[1]. Man-made sources include:
- CT scans
- X-ray imaging
- Nuclear imaging
- Bone density tests
- Mammograms
The exposure from each of these tests can vary widely based on the type of imaging being performed, the machine used, the duration of the scan, and the size of your body[5]. It should be noted that in real terms, the amount of exposure from these tests is low. For reference, the amount of ionizing radiation from a single cross-country flight ranges from 0.02-0.05 mSv[6]
Non-ionizing radiation: exposure paths
Like ionizing radiation, non-ionizing radiation has both natural and manmade sources. Ultraviolet radiation from the sun (or from artificial sources such as tanning beds and black lights) is the highest-frequency form of non-ionizing radiation, and the only form of non-ionizing radiation that has been definitively linked with cancer[7].
Radiofrequency and microwave radiation are also common, and can be both naturally occurring or manmade. Some common sources of radiofrequency include[8]:
- Radio and television signals
- Cell phones, cell towers, satellite phones, and cordless phones
- Millimeter wave scanners (full-body scanners used for security screenings
- Radar
- Bluetooth and wifi
Health risks from radiation
Both ionizing and non-ionizing radiation can pose significant health risks, though the risks from ionizing radiation are better established and much more serious.
- Cancer: Ionizing radiation has been linked to almost every type of cancer, with the amount of exposure directly tied to risk increase. Natural population studies–including studies of the survivors of Hiroshima–have shown that exposure in childhood, when bodies are still growing and cells divide much more rapidly, is much more dangerous[9].
Other than UV radiation, non-ionizing radiation has not been definitively linked to cancer. Studies exploring the possible links between non-ionizing radiation and cancer are ongoing, but for now, the International Association for Research on Cancer has labeled radiofrequency radiation as “possibly carcinogenic”[8] - Fetal abnormalities: At high doses[10], ionizing radiation can lead to fetal abnormalities and birth defects. Cells that divide and grow faster are more sensitive to the effects of ionizing radiation, which means that even levels of exposure that might be considered low-risk for adults could carry much more significant risks for unborn children, as well as for children and adolescents[11]. The risk is particularly high between 8 and 15 weeks of pregnancy.
- Tissue damage: High doses of either ionizing radiation or non-ionizing radiation can lead to burns and tissue damage[8]. Very high doses of ionizing radiation can lead to more extreme health effects, including radiation sickness or death, but the levels of exposure required are extremely high (such as the amount of radiation exposure one would receive in the near vicinity of an atomic blast).[9]
How to reduce exposure
There are many ways to reduce exposure to both ionizing and non-ionizing sources of radiation:
- Fly less frequently: All passengers and crew on a flight are exposed to higher levels of cosmic radiation while at altitude. Reducing your time in the air is the most effective way to reduce this form of exposure.
- Remediate radon: After smoking, radon is the biggest cause of lung cancer. If testing shows that your home or workplace has high levels of the gas, there are several steps you can take to help reduce concentrations.
- Discuss radiation risk from medical imaging with your physician: For the average individual, one of the most controllable sources of ionizing radiation is medical diagnostics. Preventative screening for common conditions (such as mammograms to detect breast cancer) offer huge benefits with a negligible radiation exposure. For some screening, however, it’s possible that an alternative form of imaging may lower overall radiation exposure. For example, MRIs and ultrasounds don’t rely on radiation, and low-dose CT scans use about one-fifth the amount of radiation as a standard CT scan. If you are concerned, it is important to talk to your doctor about whether any recommended high-dose diagnostic imaging is necessary. Additionally, it is important not to actively seek out scans to feel assured that you have had a ‘thorough check-up,’ as CT scans rarely provide actionable medical information in people without relevant symptoms.
Radiation exposure, particularly exposure to ionizing radiation, is convincingly tied to an increased risk of cancer and other serious health issues. Reducing your exposure when possible is recommended.
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