This Statement was prepared to give you information about uranium and to emphasize the human health effects that may result from exposure to it. The Environmental Protection Agency (EPA) has identified 1,177 sites on its National Priorities List (NPL). Uranium has been found above background levels at 26 of these sites. However, we do not know how many of the 1,177 NPL sites have been evaluated for uranium. As EPA evaluates more sites, the number of sites at which uranium is found may change. The information is important for you because uranium may cause harmful health effects and because these sites are potential or actual sources of human exposure to uranium.
When a radioactive chemical is released from a large area such as an industrial plant, or from a container such as a drum or bottle, it enters the environment as a radioactive chemical emission. This emission, which is also called a release, does not always lead to exposure. You are exposed only when you come into contact with the radioactive chemical. You can come into contact with it in the environment through breathing air, eating, drinking, or smoking substances containing the radioactive chemical. Exposure may also result from skin contact with the radioactive chemical alone, or with a substance containing it. Exposure can also occur by being near radioactive chemicals in concentrations that may be found at hazardous waste sites or at industrial accidents.
If you are exposed to a hazardous substance such as uranium, several factors will determine whether harmful health effects will occur and what the type and severity of those health effects will be. These factors include the dose (how much), the duration (how long), the route or pathway by which you are exposed (breathing, eating, drinking, or skin contact), the other chemicals to which you are exposed, and your individual characteristics such as age, sex, nutritional status, family traits, life style, and state of health.
Natural uranium is composed of three forms (called isotopes) of uranium: uranium-234, uranium-235, and uranium- 238. The amount of uranium-238 in natural uranium is more than 99%. Uranium-235 is present at just 0.72%, in natural uranium, but it is more radioactive (and therefore more hazardous) than uranium-238. Uranium-235 is used in nuclear bombs and nuclear reactors. An industrial process by which the percent of uranium-235 is concentrated is called enrichment, and the uranium obtained this way is called enriched uranium. Uranium-234 is even less abundant than uranium-235, so it can be ignored for most practical purposes.
Uranium-238 is not stable but breaks down into two parts. This process of breaking down is called decay. The decay of uranium-238 produces a small part called "alpha" radiation and a large part called the decay product. The breakdown of uranium-238 to its decay products happens very slowly. In fact, it takes about 4.5 billion years for one-half of the uranium-238 to break down (4.5 billion years is the half-life of uranium-238). Thorium, the decay product of uranium, is also not stable, and it continues to decay until stable lead is formed. During the decay processes, the parent uranium-238, its decay products, and their subsequent decay products release a series of new elements and radiation, including such elements as radium and radon, alpha and beta particles, and gamma radiation. Alpha particles cannot pass through human skin, whereas, gamma radiation passes through more easily.
Because of the slow rate of decay, the total amount of natural uranium in the earth stays almost the same, but it can be moved from place to place through natural processes or by human activities. When rocks are broken up by water or wind, uranium becomes a part of the soil. When it rains, the soil containing uranium can go into rivers and lakes. Mining, milling, manufacturing, and other human activities also move uranium around natural environments.
We use uranium mainly in nuclear power plants and nuclear weapons. Very small amounts are used in making some ceramics, light bulbs, photographic chemicals, and household products.
However, people who work at factories that process uranium, work with phosphate fertilizers, or live near uranium mines have a greater chance of being exposed to uranium in the air than most other people. Larger-than- normal amounts of uranium might also enter the environment from accidental discharges from uranium processing plants.
Since uranium is present all over the earth, everyone normally eats or drinks a small amount of uranium daily. When it enters your body this way, about 99% of it leaves within a few days in your feces and never enters your blood. A small amount of uranium (about 1%) will enter the blood. Most of this will pass through the kidney and be eliminated in the urine in a few days. A small amount goes to your bones and may stay in your bones for years. A very small amount, about 1/5000th of the weight of an aspirin tablet, is found in most people, mainly in their bones.
Although uranium is radioactive, the type of radiation it gives off cannot go through your skin, so natural uranium that is outside the body is not hazardous. When uranium gets inside your body, after breathing it in, eating or drinking it, or through cuts in your skin, radiation and chemical toxicity are of concern to health.
There is always a concern about getting cancer from any radioactive material. Natural uranium has very low levels of radioactivity and has not definitely been shown to cause cancer in humans or animals. Nevertheless, it is possible that you could develop cancer from swallowing or breathing large amounts of natural uranium because the greater your exposure to a radioactive material, the greater your chance of developing cancer. This is particularly true for enriched uranium that has been made more radioactive. Cancer may develop many years after swallowing or breathing a radioactive material. Just being near natural uranium is of very little danger to your health because most of the radiation given off by uranium cannot go through your skin.
We do not know if natural uranium causes reproductive effects or birth defects in humans, but animal studies suggest that uranium may affect reproduction and the developing fetus.
Animals that ate food, drank water, or breathed air that had high levels of uranium dust have developed kidney damage. The extent of kidney damage depends on how much uranium gets into their bodies and on the chemical form to which the animals are exposed. Animals can eat or breathe large amounts of some forms of uranium without having any health problems at all.
Tables 1-1, 1-2, 1-3, and 1-4 show the relationship between uranium and known health effects.
Since uranium is known to cause kidney damage in humans and animals, urine tests can be used to see if you have kidney damage that may have been caused by exposure to uranium. Some of these tests include measuring the amount of protein, sugar, or enzymes in the urine, or detecting the presence of damaged kidney cells in the urine. These tests, however, are not specific for uranium and are only useful to determine if kidney damage has occurred.
If you breathe large amounts of radioactive uranium, the amount of radioactivity in your body can be measured by a special test. This test is only useful if you have been exposed to certain types of uranium that stay in the lungs for a long time, or to enriched uranium that is more radioactive than normal.
