What Is Radiation?
Radiation is the transmission of energy through space or a medium. The transmission is in the form of waves or particles. Some radiation is naturally created, while others are artificially made.
There are two types of radiation depending on how they affect other atoms and molecules.
Non-ionizing radiation: This is the type of radiation that human beings are regularly exposed to. The radiation is not strong enough to affect atoms and molecules in the body.
Types of non-ionizing radiation
- Microwaves
- Global Positioning Systems (GPS) signals
- AM and FM signals
- Cellular signals
- Television signals
- Infrared signals
Ionizing radiation - This radiation is strong enough to ionize atoms and molecules. Ionization is the process of removing an electron from an atom and making it positively charged. Ionization causes electron/proton imbalance in the atoms, and this affects the cells in the body.
| Types of ionizing radiation | |
| Alpha radiation | It consists of two protons and two neutrons. It cannot penetrate past the outer skin and causes no damage |
| Beta Radiation | It consists of fast-moving electrons. It can penetrate the outer skin and is used to treat superficial tumors. |
| Gamma Radiation | It consists of protons that have neither electric charge nor mass. As a result, the radiation penetrates through the skin and leads to cell damage. |
| X-rays | X-rays are man-made electromagnetic radiation. X-rays are similar to gamma rays and can penetrate the human body. |
| Neutron radiation | It consists of free neutrons produced in large numbers due to nuclear fission or fusion reactions. |
Sources Of Ionizing Radiation
There are two categories of ionizing radiation sources - natural and artificial.
Natural Sources Of Ionizing Radiation
According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), there are four natural sources of ionizing radiation.
- Cosmic radiation - These rays reach the earth’s surface from the sun and other solar system elements. People living in higher altitudes are more exposed to cosmic radiation.
- Terrestrial radiation - Minerals like uranium, thorium, and potassium, when decayed, release a small amount of ionizing radiation. Some of these minerals are found in materials used for building construction, and hence people may be constantly exposed to minimal amounts of terrestrial radiation in closed spaces.
- Radiation exposure through inhalation - Radiation gases like radon, actinon, and thoron are produced due to radioactive mineral decay. Though harmless generally, some closed spaces like mines may have an excess of these gases.
- Radiation exposure through ingestion - Minimal amounts of radioactive minerals are found in drinking water and food cultivated in soil. These reach the human body through ingestion.
Artificial Sources Of Ionizing Radiation
- Medical radiation - Radiation is a standard method to diagnose various health conditions. X-ray machines, Computerized Tomography (CT) scan devices, and particle accelerators are all types of equipment that use ionizing radiation. About 98% of all the artificial sources of ionizing radiation are generated in the medical industry. According to the World Health Organization (WHO), 3600 million diagnostic radiology treatments happen globally using some kind of radiation.
- Nuclear power plants - Nuclear power plants use nuclear reactions to create electricity. Such plants produce ionizing radiation.
- Industries and agriculture - Many industrial and agricultural practices make use of radiation in their everyday processes.
Radiation Exposure As A Breast Cancer Risk Factor
Radiation exposure can cause breast cancer in different ways.
- It can alter DNA and lead to abnormal growth and multiplication of cells.
- It causes genome instability (changes in genes that can lead to problems in cell growth and multiplication)
- It can affect how breast cells interact, multiply, and grow.
Researchers studied the effect of radiation exposure on Japanese women who survived the atomic bombing of 1945. The study identified 807 first-time breast cancer cases and 20 second-time breast cancer cases in the survivors. The study reported the following:
- People who were exposed to a higher dose of radiation had a higher risk of developing breast cancer.
- Women under 20 years during the bombing had a higher risk of breast cancer than women older than 40 during the bombing.
Does Mammography Increase Breast Cancer Risk?
Mammography is a diagnostic procedure that uses X-rays to check for breast cancers. In a diagnostic mammogram, a minimum of two X-ray films of the breasts is taken at two different angles. On average, the dose of radiation for these two pictures is 0.42 mSv (millisieverts). Dosage is the amount of ionization that occurs due to radiation exposure.
According to the National Breast Cancer Foundation, women over 40 years are advised to get their annual mammographic screening done. In addition, doctors may recommend more frequent screening in the following cases.
- The woman has a family history of breast cancer.
- The woman has dense breasts, making it challenging to identify lumps.
According to a study, women with large, dense breasts who undergo repeated mammography may be at higher risk for radiation-induced breast cancer and breast cancer death.
The researchers projected that "annual digital mammographic screening of 100,000 women (aged 40 to 74) would induce 125 cases (~0.1%) of breast cancer, and that there would be 16 deaths (0.016%)."
However, this number appears to be almost negligent when compared to the 968 breast cancer deaths (9.7%) that would have been averted by early detection from screening.
The Genetic Angle
The H19 Gene
The H19 gene helps produce a molecule called the non-coding RNA. The non-coding RNA is considered to be a tumor suppressor and is protective against different kinds of cancers. Certain changes in this gene can encourage the growth and multiplication of radiation-damaged cells. This can lead to tumors.
rs2107425 is a single nucleotide polymorphism or SNP in the H19 gene. A particular study reports that people with the A allele of this SNP, are at a higher risk for developing breast cancer when exposed to high doses of radiation.
The ERCC2 Gene
The ERCC2 gene helps make a protein called XPD (Xeroderma Pigmentosum complementation group D). It plays a role in repairing damaged DNA.
rs13181 is an SNP in the ERCC2 gene. In people with the wild AA genotype of this SNP, there is an association between occupational radiation exposure and breast cancer.
However, this association is not seen in the AC and CC genotypes.
| Genotype | Implications |
| AA | Association between occupational radiation exposure and breast cancer |
| AC | No association between occupational radiation exposure and breast cancer |
| CC | No association between occupational radiation exposure and breast cancer |
Non-genetic Factors Influencing Radiation Exposure And Breast Cancer Risk
Age
Studies show that women under 20 are at the highest risk for developing breast cancer due to radiation exposure. According to these studies, women above 50 years have minimal or no recorded risk for radiation-induced breast cancer.
Excess Exposure to Radiation
Few women may have undergone radiation therapy in the past, increasing the risk of breast cancer. Some women who are in the high-risk category include:
- Women with childhood cancer and extended periods of radiation therapy
- Women with a prior breast cancer diagnosis who have undergone radiation therapy
- Women with a history of tuberculosis or scoliosis that were diagnosed and monitored with X-rays
- Breastfeeding women who were treated with X-rays for breast inflammation (postpartum mastitis)
Reproductive History
The periods of pregnancy bring down the risk of radiation-induced breast cancer. Women who have an early full-term pregnancy are more protected against breast cancer.
According to some studies, during pregnancy and breastfeeding, the number of weak breast cells affected by radiation is lesser, bringing down breast cancer risk.
Family History
Family history affects the relationship between radiation exposure and breast cancer. The Family history affects the relationship between radiation exposure and breast cancer. The BRCA1 and BRCA2 gene changes lead to inherited breast cancer.
Women with changes in these genes are already at a higher risk of developing breast cancer. Radiation exposure can increase the risk.
Limiting Radiation Exposure To Reduce Breast Cancer Risk
Get A Mammogram Only When Absolutely Needed
According to the American Cancer Society, women between the ages of 40 and 44 can start screening for breast cancer but don’t have to get mammograms unless their doctors instruct. Women between 45 and 54 need to get one mammogram a year. Women older than 55 should get two mammograms done a year.
If you are younger than 40, talk to your doctor and only get a mammogram if necessary. While mammogram screening helps identify tumors early and treat breast cancer early, getting unnecessary mammograms may trigger breast cancer in a few.
Check Your Occupational Exposure To Radiation
Occupational radiation exposure happens in workplaces when the person handles radioactive sources or works with equipment generating radiation.
- Talk to your management about the risks of radiation exposure
- Understand the dosage of radiation you are exposed to every day
- Increase your distance from the radiation source
- Use the right shielding equipment and protective gear to bring down the risk of radiation exposure
Control Other Factors That Lead To Breast Cancer
Lifestyle habits like smoking and drinking, excessive weight gain, the types of food you choose, and exposure to other environmental carcinogens can all lead to breast cancer.
Unhealthy lifestyle choices, along with radiation exposure, increases breast cancer risk drastically.
- Quit smoking and have alcohol in moderation.
- If you are overweight or obese, work on bringing down body fat.
- Limit consumption of charred meat, processed foods, and sugars and include a lot of fresh fruits, vegetables, grains, and legumes.
Opt For Genetic Testing
Genetic testing will help identify how harmful radiation exposure is for your breast cells. You can also know if you are at risk for developing inherited breast cancer because of the abnormal functioning of the BRCA1 and BRCA2 genes.
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Summary
- Radiation is the transmission of energy through space or a medium. Non-ionizing radiation is harmless and does not affect the human body.
- Ionizing radiation causes cellular-level changes and can lead to cancer.
- Radiation exposure can alter DNA, cause genome instability, affect the way breast cells interact, and lead to breast cancer.
- Mammography is a radiation procedure to identify tumor cells in the breasts. Women who undergo excess mammography procedures under the age of 40 may be at a higher risk of developing breast cancer in the future.
- Mammography also seems to retrigger second breast cancer in some women who have gone through first breast cancer and radiation therapy before the age of 45.
- Changes in the H19 and ERCC2 genes can increase the risk of breast cancer upon radiation exposure.
- Younger women are at higher risk for developing breast cancer on exposure to radiation. Pregnancy and breastfeeding periods are protective against breast cancer.
- Avoiding mammography unless required, using protective shields and gear while working near radiation, and following a healthy lifestyle can all bring down breast cancer risk.
- Genetic testing helps know if a person is at higher risk for breast cancer because of radiation exposure.
References
- https://www.who.int/news-room/fact-sheets/detail/ionizing-radiation-health-effects-and-protective-measures
- https://www.cdc.gov/nceh/radiation/what_is.html
- https://www.epa.gov/radiation/radiation-sources-and-doses
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1064116/
- https://www.nature.com/articles/s41467-018-05266-6
