Radioactive elements7/14/2023 The heavier person will receive a greater internal dose because the decay of the 40K produces other low-penetrating radiation (beta radiation) that deposits its energy within the body. In both cases, however, the dose rate will be extremely small compared to the normal background dose rate. If a person is above average in weight, the dose rate outside of this person's body will expectedly be higher than the dose outside the body of a lower-weight individual. These will be moving in all directions, some will be attenuated in the body, and the dose rate from these gamma rays outside of the individual's body will represent a very small fraction of the normal background dose rate from all natural sources outside the body. A gamma ray is emitted in about one out of every 10 disintegrations of 40K, implying that about 500 gamma rays are produced each second. Second, 40K emits gamma rays in a little over 10 percent of its decays and most of these gamma rays escape the body. The amount of the radioactive isotope 40K in a 70-kg person is about 5,000 Bq, which represents 5,000 atoms undergoing radioactive decay each second. Potassium is ingested in many foods that we eat and is a critically important element for proper functioning of the human body it is present in pretty much all the tissues of the body. First, the 40K concentration in the body is fairly high. Potassium-40 ( 40K) is the primary source of radiation from the human body for two reasons. This radionuclide has been around since the birth of the earth and is present as a tiny fraction of all the potassium in nature. The major one that produces penetrating gamma radiation that can escape from the body is a radioactive isotope of potassium, called potassium-40. A pie chart in this report shows dose contributions from various natural background radiation sources, and the contribution from our own bodies can be found by adding the dose from potassium-40 and from thorium and uranium and their decay products (discussed in more detail below).Īll of us have a number of naturally occurring radionuclides within our bodies. More information is available in the National Council on Radiation Protection and Measurements (NCRP) Report 160, Ionizing Radiation Exposure of the Population of the United States. For women and children, the dose is less, in rough proportion to their smaller bodies. man who weighs 70 kg receives each year from all sources of natural background radiation (not including medical sources). This is about one-tenth (or 10 percent) of the 3.1-mSv dose that the average U.S. These substances are absorbed by our bodies, into our tissues, organs, and bones, and are constantly replenished by ingestion and inhalation.įrom the radionuclides that are present in our bodies, the average man in the United States receives an effective dose of about 0.3 mSv each year. Yes, our bodies are naturally radioactive, because we eat, drink, and breathe radioactive substances that are naturally present in the environment.
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