_______________________________ DCA05DR Dental Radiation Health, Safety, and Protection, 3rd Edition
Terrestrial radiation is emitted from radioactive materials—such as potassium and the radioactive decay products of uranium and thorium—present in the earth and air. Terrestrial radiation has been measured in the air over a large segment of the United States. The dose of terrestrial radiation varies by location, with the highest doses in the mountains of the western states as granite and metamorphic rocks in the Rocky Mountains and the Sierra Nevada Mountains contain higher amounts of uranium compared to the sedimentary rocks of the east coast (Alden, 2020). Terrestrial radiation makes up approximately 3.0% of all radiation exposure received by individuals in the United States (Health Physics Society, 2020). Persons living on the Atlantic or Gulf Coasts receive approximately 0.23 mSv annually, and persons living on the Colorado Plateau receive approximately 0.90 mSv in a given year (Omni Calculator, 2024). Radon is the single largest contributor to the phenom- enon of natural radiation. A gaseous element resulting from the disintegration of isotopes of radium (which is itself a product of the decay of uranium in the soil), radon can be found in the soil and rocks underneath houses, in well water, and in certain building materials (World Health Organization, 2023). As radium disintegrates, large amounts of radon accumulate in areas where airflow is poor, such as in caves, mines, or the basements of energy-efficient homes (World Health Organiza- tion, 2023). As people breathe, they inhale radon. The EPA estimates that radon and its decay products cause more than 21,000 cases of lung cancer annually and is behind smoking as the second leading cause of lung cancer in the United States (Environmental Protection Agency, 2024).
marily as a result of greater use of computed tomography (CT) and nuclear medicine procedures. The relative percentages of artificial sources of radiation are: • Computed tomography (CT scan): 24% • Nuclear medicine: 12% • Interventional fluoroscopy: 7% • Conventional radiography/fluorography: 5% (Health Physics Society, 2020). In the last category, dental imaging contributes less than 1% of the annual effective dose from all sources of medical imag- ing (American Dental Association, 2024). This percentage does not include cone beam computed tomography (CBCT) examinations, which are on the rise in dentistry. The effective dose of radiation from a dentoalveolar CBCT with a small and medium field view ranges from 0.019 to 0.652 mSv while an effective dose of 0.068-1.073 mSv accrues from a maxillofacial CBCT with a large field of view (Benavides et al., 2024). Table 2 lists some common diagnostic procedures, along with their effective doses of radiation. Consumer products and activities, industrial sources , and occupa- tional exposure also contribute to the amount of artificial radia- tion received by the U.S. population, although the amount of radiation received in this way is small. Sources derived from consumer products and activities include building materials, commercial air travel, cigarette smoking, mining and agricul- ture, combustion of fossil fuels, road construction materials, television, and glass and ceramics, and they contribute approxi- mately 2% of the total annual effective dose per person (U.S. Nuclear Regulatory Commission, 2020). Industrial radiation includes sources such as nuclear power generation; disposal of nuclear waste; airport inspection systems; and industrial, medical, educational, and research activities. Occupational exposure is employee-related radiation exposure that occurs in a variety of work situations, such as medical (includes dental and veterinary medicine), aviation, nuclear power, military, academic, and industrial environments. Among occupationally exposed individuals, the medical and aviation categories com- prise the greatest number of workers and the highest collective effective dose. Individuals in the aviation industry experience a higher concentration of natural radiation at higher altitudes due to a higher amount of radiation from cosmic rays present at higher altitudes than the level of cosmic radiation at ground level (Alden, 2020). However, industrial and occupational sources combined account for less than 0.01% of the total annual effective dose per person. Table 3 summarizes radiation sources and exposure doses, revealing that the radiation from natural and artificial sources results in an average effective dose of 6.2 mSv per year for persons living in the United States (U.S. Environmental Pro- tection Agency, 2021b).
Self-Assessment Question
2. Terrestrial radiation: A) Remains at a constant level throughout the United States. B) Is the source of approximately 30% of all radiation exposure for people in the United States. C) Is present from radioactive materials in the Earth and the air. D) Features potassium as the largest contributor of natural radiation. ARTIFICIAL RADIATION Artificial radiation (also known as human-made radiation ) accounts for 50% of the radiation to which people in the United States are exposed annually (U.S. Nuclear Regulatory Commission, 2020; Health Physics Society, 2020). Artificial radiation is generated in medicine and dentistry, and it is found in consumer and industrial products. Medical diagnostic imaging is the largest contributor to artificial radiation (U.S. Environmental Protection Agency, 2021a). Radiation used in the practice of medicine includes interven- tional, nuclear medicine; medical and dental diagnostic imag- ing procedures; and radiation therapy. Exposures from medical procedures have significantly increased since the 1980s, pri-
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