What were the scientists on Amchitka in 2004 looking for?
by Doug Schneider, Alaska Sea Grant College Program
The three-bladed radiation warning symbol was developed at the University of California Radiation Laboratory in Berkeley in 1946 and was adopted by the Atomic Energy Commission in 1953. It is simple, readily identifiable and discernible at a large distance.
According to the CRESP Amchitka Study Plan, a suite of radionuclides was selected for analysis, based on information obtained from the groundwater models and human health risk assessments and existing knowledge of radionuclides of interest for human health, ecological health and source identification. Since the Amchitka radiation information remains classified, the suite of isotopes listed below, identified in the Amchitka Science Plan, was reviewed by people with appropriate clearance and access to provide advice if our selection list was missing key isotopes. They indicated that the isotopes the scientists were examining were appropriate.
- Americium 241 Americium is a man-made metal produced when plutonium atoms absorb neutrons in nuclear reactors and in nuclear weapons detonations. Americium has several different isotopes, all of which are radioactive. The most important isotope is Am-241. Most americium 241 in the environment originates from the atmospheric testing of nuclear weapons during the 1950’s and 1960’s. While most of the shorter-lived radionuclides have now decayed away, longer-lived radionuclides such as americium 241 will remain in the environment for many years. However, since they decay slowly, they emit radiation slowly, so the dose is very low and will decline. Americium 241 poses a significant risk if swallowed or inhaled. It can stay in the body for decades and increase the risk of cancer. Source: U.S. EPA
- Cesium 137 (Cs-137) Cesium is a soft, malleable, silvery white metal. The half-life of cesium 137 is 30 years. Radioactive cesium 137 is produced when uranium and plutonium undergo fission. Examples of the uses of this process are nuclear reactors and nuclear weapons. People may ingest cesium 137 with food and water, or may inhale it as dust. If cesium 137 enters the body, it is distributed fairly uniformly throughout the body’s soft tissues, resulting in exposure of those tissues to radiation. Slightly higher concentrations of the metal are found in muscle, while slightly lower concentrations are found in bone and fat. Cesium 137 is known to cause cancer. Source: US EPA
- Cobalt 60 (Co-60) Cobalt is a metal that may be stable (non-radioactive, as found in nature), or unstable (radioactive, man-made). The most common radioactive isotope of cobalt is cobalt 60. Non-radioactive cobalt occurs naturally in various minerals and has been used for thousands of years to impart blue color to ceramic and glass. The radionuclide, cobalt 60, is produced for commercial use in linear accelerators. It is also produced as a by-product of nuclear reactor operations. People may ingest cobalt 60 with food and water that has been contaminated, or may inhale it in contaminated dust. Once in the body, some cobalt 60 is quickly eliminated in the feces. The rest is absorbed into the blood and tissues, mainly the liver, kidney and bones. Absorbed cobalt leaves the body slowly, mainly in the urine. Cobalt 60 is known to cause cancer. Source: U.S. EPA
- Europium 152 (Eu-152) Europium 152 is a silvery white metal produced as a byproduct of nuclear reactors and nuclear weapons testing. Europium 152 has a half-life of 13 years. Europium can be ingested by eating contaminated food, drinking water or breathing contaminated air. Europium is not well absorbed into the body after intake, with only about 0.05% of the amount ingested being absorbed into the bloodstream through the digestive tract. Of the europium that reaches the blood, 40% is deposited in the liver, and another 40% is deposited on the surface of the bone, where it can irradiate the bone-forming cells. This deposited europium is retained in the body with a biological half-life of almost 10 years; an additional 6% of the absorbed europium is deposited in the kidneys, where it is retained with a short biological half-life of 10 days. Europium is associated with the increased likelihood of liver and bone cancer. Source: Argonne National Laboratory
- Iodine 129 (I-129) Iodine is a nonmetallic solid element. There are both radioactive and non-radioactive isotopes of iodine. Iodine 129 and 131 are the most important radioactive isotopes in the environment. Both iodine 129 and iodine 131 are produced by the fission of uranium atoms during operation of nuclear reactors and by plutonium (or uranium) in the detonation of nuclear weapons. Iodine 129 has a half-life of 15.7 million years; iodine 131 has a half-life of about 8 days. Source: U.S. EPA
- Plutonium 238, 239, 240 (Pu) Plutonium is a silvery-grey metal that becomes yellowish when exposed to air. It is solid under normal conditions and is chemically reactive. Plutonium has at least 15 different isotopes, all of which are radioactive. The most common ones are plutonium 238, plutonium 239 and plutonium 240. Plutonium 238 has a half-life of 87.7 years. Plutonium 239 has a half-life of 24,100, and plutonium 240 has a half-life 6,560 years. Plutonium was dispersed world wide from atmospheric testing of nuclear weapons conducted during the 1950s and ’60s. The fallout from these tests left very low concentrations of plutonium in soils around the world. External exposure to plutonium poses very little health risk. Internal exposure to plutonium is an extremely serious health hazard. It generally stays in the body for decades, exposing organs and tissues to radiation and increasing the risk of cancer and kidney damage. Source: U.S. EPA
- Strontium 90 (Sr-90) Strontium 90 is a by-product of the fission of uranium and plutonium in nuclear reactors and in nuclear weapons. Large amounts of Sr-90 were produced during atmospheric nuclear weapons tests conducted in the 1950s and 1960s and dispersed worldwide. Strontium 90 has a half-life of 29.1 years. Everyone is exposed to small amounts of strontium 90, since it is widely dispersed in the environment and the food chain. Dietary intake of Sr-90, however, has steadily fallen over the last 30 years with the suspension of nuclear weapons testing. Strontium 90 behaves chemically much like calcium and therefore tends to concentrate in the bones and teeth, and increases the risk of cancer. Source: U.S. EPA
- Technetium 99 (Tc-99) Technetium 99 is a silver-gray, radioactive metal. It occurs naturally only in very small amounts. Technetium 99 has a radioactive half-life of 212,000 years. Technetium 99 is produced in commercial quantities mainly as a byproduct from the operation of nuclear reactors and nuclear weapons. Ingestion of contaminated food or water is the primary way technetium gets into the body. Once in the human body, technetium 99 concentrates in the thyroid gland and the gastrointestinal tract. The body, however, excretes half of the ingested technetium 99 within 60 hours. It continues to excrete half of the remaining technetium 99 every 60 hours that follow. After 120 hours, only one-fourth of the ingested technetium 99 remains in the body. Source: U.S. EPA
- Uranium 234, 235, 236, 238 (U) Uranium is present naturally in virtually all soil, rock and water. When refined, uranium is a silvery white, weakly radioactive metal. Uranium isotopes can be separated to increase the concentration of one isotope relative to another. This process is called "enrichment." Uranium 238, the most common natural form, has a half-life of 4.47 billion years, while uranium 235 has a half-life of 700 million years. Uranium 234 has a half-life of 246,000 years. The greatest health risk from large intakes of uranium is toxic damage to the kidneys and risk of cancer due to its radioactivity. Since uranium tends to concentrate in specific locations in the body, risk of cancer of the bone, liver cancer and blood diseases (such as leukemia) are increased. Inhaled uranium increases the risk of lung cancer. Source: U.S. EPA