12.9  Potential Impacts of Radionuclides on the Human Body[1]

12.9.1  Plutonium 239 Health Effects: 

Insoluble plutonium particles that can be inhaled are retained in the respiratory tract (lungs and esophagus).  Lung cancer has been observed in animal tests.  27 micrograms has been known to cause cancer[3].  27 micrograms is about 1 millionth of an ounce. Plutonium travels from the lungs to the blood and lymph system.

Soluble plutonium enters the blood quickly and deposits on bone surfaces and in the liver.  About 40% of the plutonium that enters blood goes to bone surfaces, 40% to the liver, and the rest to muscles.  Bone and liver cancer can result, because plutonium is retained in these tissues for long periods.  Leukemia, a cancer of the blood, may be caused by plutonium retention in the bone marrow.

The alpha particles emitted from plutonium can also cause genetic damage.  Plutonium workers at British Nuclear Fuels, Sellafield, England, have experienced chromosome aberrations due to plutonium inhalation.  Rocky Flats workers have increased cases of brain cancer. Plutonium has also been associated with pituitary and other rarer cancers.

In general, plutonium has a long time lapse between exposure and when cancers are diagnosed of about 30 years, but this can vary according to the does received.

Figure 12.9  Effects of Plutonium Alpha Radiation in Lung Tissue in 48 Hours[2]

12.9.2  Tritium Health Effects

Tritium can be inhaled, ingested through air and food, or absorbed through the skin.  Tritium is biologically concentrated in tissues as it passed through the food chain, from plants to herbivores to carnivores.  In animal tests, it can pass to a fetus or through mother’s milk.  Tritiated water can pass through the human body in 12 days. But when it unites with carbon in living tissues, becoming what is known as “organically bound tritium” or OBT, it can remain in human tissue for 450 to 650 days.  OBT contributes 90% of the radiation dose.

After entering the body, tritium mixes with body water to create a whole body dose, and irradiates the body somewhat uniformly.  Fetal tissue, testes and bone marrow are damaged most easily by this method.  Tritium also accumulates in the blood, heart, and kidney cells.  It seems to be retained longest in muscle tissue.  High internal dosage of tritium is possibly associated with leukemia, blood disorders, and testicular cancer.

12.9.3  Strontium-90 Health Effects

Strontium-90 has been found in the top ten centimeters of soil downwind from the Nevada Test Site and Chernobyl.  Radioactive strontium is biologically retained in human bones.  Chemically, it resembles calcium (or natural strontium) and the human body does a poor job of distinguishing between the two.  Cancer of the bone and leukemia was observed in exposed animals.  Leukemia was caused more readily by continuous low doses than by a single high dose.  High doses caused disproportionately more bone cancers than low doses.  There is also evidence for a weakening of the immune system.

12.9.4  Cesium-137 Health Effects

Strontium-90 has been found in the top ten centimeters of soil downwind from the Nevada Test Site and Chernobyl, especially in areas where it rained after nuclear events.  Cesium has been found in harvestable plant materials, such as tobacco and mushrooms.  It is thought to be the second major contributor to radiation dose after the short-lived iodine-131 has decayed.  It is easily absorbed into the blood and contributes to a whole-body dose of radiation.  Cesium is similar to potassium, and when cesium is ingested, it may impede functioning of potassium in the nervous system.  Potassium is essential for proper nerve functioning, but no such health effects have been proven. 

High doses of injected cesium result in death from bone marrow destruction, much like high doses of X-rays.    Lower doses of cesium cause cancer in animals, particularly liver cancer.

12.9.5  Uranium (All Isotopes)  Health Effects[4]

Outside the body, plutonium and uranium pose minimal risks to human health unless exposure is on a sustained basis. This is because the main type of radiation from both materials, alpha radiation, is very short-range and is stopped by the outer dead layer of skin.  However, if plutonium or uranium gets into the body, the high-energy alpha radiation can damage cells and cause cell mutations that can lead to cancer. Like plutonium, uranium is a health hazard when small particles are inhaled or absorbed through wounds. But uranium is also more easily absorbed than plutonium though the gastrointestinal tract. Animal studies suggest that uranium- like plutonium, may damage reproductive organs, may harm a developing fetus, and may increase the risk of leukemia and soft tissue cancers. Uranium is far less radioactive and therefore less carcinogenic than plutonium, and uranium can cause acute damage to the kidneys by heavy metal poisoning well before radiation effects are manifest.

One of the most serious health hazards associated with uranium is uranium mining.  A study of uranium miners conducted by the U.S. Public Health Service between 1948 and 1982 showed significant excesses of respiratory cancers; by 1978, white underground miners in the study suffered five times the expected rate of such cancers. The cancer risk from uranium mining is mainly due to exposure to the decay products of radon, which is itself a decay product of uranium-238.

Uranium used to produce enriched uranium for U.S. nuclear warheads was mined before the mid-1960s.  Mines operating since then have produced uranium for commercial purposes and to a lesser extent for the reactors that propel some naval vessels.

Most uranium mines in the U.S. have been shut down, but the radioactive wastes from uranium processing still pose a health risk to segments of the U.S. population. These wastes, called mill tailings, contain long-lived radioactive isotopes. As of the late 1980s, some 220 million metric tons of mill tailings had accumulated from uranium production for nuclear weapons and nuclear power.

According to the Environmental Protection Agency, groundwater has become contaminated at virtually all mill tailings sites.