Uranium was discovered by Klaproth in 1789 - the year George Washington was inaugurated as first president of the United States. It was named after the planet Uranus, discovered in 1781. During the 19^th and early 20^th centuries uranium was used mainly as a yellow colorant in pottery glazes and glass (canary glass).

Uranium is the heaviest element found in the earth with sufficient abundance for commercial extraction - it is more abundant than silver or gold.

Uranium is 19 times denser than water and 1.7 times denser than lead: a piece the size of a 1 qt. milk carton would weigh 38 lbs. The atomic bomb that destroyed Hiroshima contained less than 38 lbs of uranium as the nuclear explosive.

Uranium metal is very reactive and corrodes easily. It must be protected from air in order to keep its metallic properties. If not protected from air it forms uranium oxide. Consequently, it is not suitable as a metal for consumer or industrial products.

Uranium is pyrophoric - it will burn when heated in air, going up in smoke and forming fine particles of uranium oxide that can be inhaled without noticing. Pyrotechnics, or fireworks displays, use various elements to give different colors when they burn.

In 1896 Becquerel discovered radioactivity when he placed uranium containing materials on a photographic plate protected with black paper. The photographic plate became exposed through the paper. This discovery was made soon after x-rays were discovered. Radioactivity is similar to x-rays.

There are 3 major isotopes of uranium - all are radioactive. U-238 has 99.28 % abundance, U-235 has 0.72 % abundance and U-234 has 0.0054 % abundance. Nuclear fission occurs with U-235 but not with U-238. It is necessary to have more than 3% U-235 in the uranium fuel in order to sustain a nuclear reaction for electric power generation - this is done by a process called enrichment.

Table 1. Half-life and radioactivity of natural uranium and depleted uranium.
 

Nuclide	Half-life  (yr)	Activity (Bq/g)	% Unat	Contribution to Acty of 1g Unat (Bq)‡
U-234	245,000	231,000,000	0.0054	12,470
U-235	704,000,000	80,010	0.711	570
U-238	4,470,000,000	12,440	99.283	12,350
			% in DU	Acty in 1 g DU (Bq)
U-234	245,000	231,000,000	0.0009	2,080
U-235	704,000,000	80,010	0.2	160
U-238	4,470,000,000	12,440	99.8	12,420

‡ 1 Becquerel (Bq) is one disintegration per second or release of one radioactive particle per second.
 

Atomic bombs require >90% U-235 or they can use plutonium, which is made by nuclear reactions from uranium. There was virtually no plutonium on earth prior to 1940, today there are thousands of tons in atomic bombs and as highly radioactive waste from nuclear reactors. The U.S. Department of Energy still has no acceptable plan for disposal of highly radioactive waste from nuclear reactors.

The enrichment process to produce fissionable U-235, i.e., increasing U-235 from 0.7 % of total uranium to >3 % results in large amounts of depleted uranium (DU) waste - about 7 tons of DU for each ton of enriched uranium for nuclear fuel. (See diagram). During the enrichment process, the fissionable U-235 is removed from some uranium leaving a waste product that is depleted in U-235 (only about 0.3% U-235 instead of 0.7% U-235) and also has less U-234. This is known as depleted uranium (DU). It has all the chemical characteristics of natural uranium, but only about 60% of the radioactivity.
 

Figure 1. The Uranium Enrichment Process produces about 1.0 ton of enriched uranium for every 8 tons of natural uranium processed and results in about 7.0 tons of depleted uranium (DU).

Civil Uses for Depleted Uranium (DU)

=> Yellow enamel used in jewelry and badges

=> Until 1980s used in dental porcelains for coloration

=> Catalyst for chemical reactions and photographic films

=> Radiation shielding for radiation therapy, medical devices and nuclear waste packaging

=> Counterweights for aircraft rudders, ailrons, elevators (the first 550 Boeing 747s used DU for counterweights but the material was unsuitable - it corroded quickly).

=> Counterweights and ballast for boats (yachts)
 

Health Effects of Uranium

Because of the long radioactive half-life for U-238 (4.5 billion years), depleted uranium (DU) and natural uranium are considered by some agencies in the U.S. government to pose minimal risk for radiation exposure, even if it is ingested or inhaled. There are low levels of uranium occurring naturally everywhere on the planet. The nuclear industry in the last half of the 20^th century has obtained large quantities of highly purified uranium and placed very high concentrations of this element in some places, much like other elements have been purified, e.g., iron, copper, gold, silver, mercury, lead, cadmium, arsenic. Some of these can be toxic in high concentrations, especially mercury, lead, cadmium and arsenic.

Uranium miners in the Colorado Plateau area had about 10 times more lung cancer than the general population. The high incidence of lung cancer among uranium miners, before radiation safety precautions were initiated, was considered to be due to the presence of high levels of radon gas in the air of the mines, although chemical carcinogenesis from uranium in the ore dust can not be ruled out as contributing to the increased cancers in these workers.
 

Lessons from Chemical Toxicity of Other Metals

Chromium is an essential mineral element in the diet as chromium III (pronounced chromium three) and is generally considered nontoxic at levels encountered in the environment, including industrial exposures. The recommended dietary allowance (RDA) for this element is less than 1 mg, an amount difficult to see with the naked eye.

Chromium VI (six), or chromate, is carcinogenic, genotoxic, embryotoxic, teratogenic (causes birth defects), causes renal tubular damage, and causes skin rashes in sensitive individuals. Workers in the chromium industry had a higher incidence of lung cancers relative to the general population. These cancers are due to chemical toxicity from chromate in dust and aerosols found in the work place. The industry has cleaned up the work place, decreasing worker exposure and decreasing the incidence of adverse health effects in this industry. Chromate is used in chrome plating, stainless steel production, pigments for paints and dyes, and in welding.
 

Lead has been recognized as a health hazard since the second century B.C. (Pliny) Lead is one of the most common toxic metals, with widespread industrial uses, including use as a gasoline additive, as a pigment in paints and pottery glazes, and is currently used for batteries, and solder for plumbing. Epidemiological evidence to "prove" lead is a carcinogen is not conclusive, but there are increased rates of lung, kidney, and stomach cancer in occupationally exposed workers. Lead has been shown to be carcinogenic in lab animals, causing mostly kidney tumors, as well as tumors of testes, lung, pituitary, prostate and adrenal glands.

Lead is known to impair neurological development in children, resulting in motor (movement) dysfunction, slower reaction time, reading disabilities and lower IQ in many (but not all) studies. Citizens and community groups have been instrumental in getting laws passed and enforced to remove lead from gasoline, paint and other products that make it an environmental hazard.
 

Mercury is toxic primarily to the nervous system, resulting in sensory impairment (numbness, especially in extremities), movement disorders (lack of coordination) that also affect speech, loss of peripheral vision, hearing impairment, and tremors. Occupational exposure has been primarily to miners, goldsmiths, mirror makers, workers in thermometer factories and chemical plants and dentists in preparing dental fillings.

Methylmercury, released from a chemical plant in Minamata, Japan, resulted in several hundred cases of neurological disease (Minamata disease) in local residents, especially fishermen and their families. The mercury poisoning often resulted in aborted fetuses, as well as a high incidence of cerebral palsy and other congenital neurological defects. (Documentary: Minamata: the Victims and Their World, 1971, Directed by Tsuchimoto Noriaki, Japanese) Thousands of people in Iraq received toxic levels of mercury from misuse of organomercury treated seeds (eating rather than planting them).
 

Cadmium has many industrial uses, including batteries (NiCad), metal coatings in electroplating, pigments in paints, enamels and plastics and is found in solder and welding electrodes. Cadmium is classified as a human carcinogen, with lung cancer the most prevalent. Cadmium has also been associated with prostate, kidney, liver, stomach and hematopoietic (system for forming blood cells) cancers. Cadmium is recognized as a potent carcinogen in rodents (lab animals), causing tumors at the injection site (sarcomas), as well as testicular tumors.
 

Note: These are just a few examples of toxic metals that have been commonly used for industrial and commercial products and processes. Although lead and mercury toxicity have been known for centuries, they are not especially toxic if handled properly and are not taken internally. The toxic effects of these metals become apparent in the industrial workplace if safety precautions are not taken to minimize workers' exposures. Over the past 30 years laws have been enacted to protect workers from exposure to these toxic metals. It is up to government agencies to enforce these laws.
 

Known Toxic Effects Associated with Uranium

The toxic effects of uranium were reported in the 1820s, although it was considered a feeble poison - a half teaspoon would kill a rabbit after 2 days. In the late 1800s, it was used as a homeopathic treatment for diabetes, although patients experienced bad side effects from uranium poisoning and the treatment was questionable in terms of curing diabetes. The homeopathic rationale was something like a hair of the dog that bit you. Uranium poisoning causes kidney damage that can lead to excretion of glucose in the urine - one of the symptoms of diabetes. Uranium was also used to treat cancers, even though it can also cause cancer.

Uranium toxicity was well established by the time the nuclear industry got going in the 1940s, so safeguards to protect workers were put in place. Miners weren't so fortunate, but any kind of mining was inherently unsafe. Occasionally workers would have accidents. They would get very ill, sometimes die, or survive with certain disabilities after drastic medical treatment was done to save them. Most exposures included a toxic soup that could have resulted in illness from any of a number of substances in the mixture. Consequently, many official government reports conclude that there is not sufficient information to establish that uranium is toxic to humans, even though most government agencies acknowledge that uranium is toxic. One could speculate what the reasons are for these conflicting viewpoints from the U.S. government.

Cancers

Uranium miners experience about 10 times as much lung cancer as the general population. Although this is attributed to the presence of radon gas in mines, uranium dust may also contribute.

It has been known for 40 years that uranium has a strong affinity for DNA. Molecular biologists have used uranium compounds to study the properties of DNA and make DNA visible under the electron microscope. Uranium causes DNA strand breaks and induces free radical mutations of DNA bases. If these changes in DNA are not properly repaired by the cells normal repair mechanisms, it will cause permanent genetic changes to take place. The more frequently this damage to the DNA occurs, the more likely it is that the damage will not get repaired. This can cause cancer, but if it takes place in sperm or egg cells, it can result in permanent genetic defects passed on to offspring. Uranium has been shown to cause cultured human cells to be transformed into cancerous cells. Implanted depleted uranium metal fragments caused soft tissue sarcomas (cancer) in rats.

Cell Death (Cytotoxicity)

Depleted uranium caused cell death in mouse macrophages, i.e., immune cells responsible for clearing DU from the body are destroyed by the DU.
 

Neurological Effects of Uranium

Uranium exposure impaired movement and coordination performance in rats. DU metal fragments implanted in rats caused changes in brain activity.
 

Reproductive and Developmental Effects of Uranium

Uranium treatment of male mice resulted in a decrease in pregnancy rate when mated with untreated females. This effect may have been due to behavioral changes that resulted from treatment with uranium, since there were not obvious changes in the sperm of these mice. Uranium in the diet for 16 weeks caused decreased testes weight, testicular lesions, and necrosis (death) of sperm cells.

Uranium given to pregnant mice resulted in reduced ossification (bone formation) of skull and bones and skeletal deformations in offspring.
 

Note: These are some examples of the toxic effects of uranium that have been scientifically demonstrated in lab animals. A list of references is available for those who wish to find the original scientific papers. The National Academy of Sciences (NAS) evaluated the scientific literature on uranium toxicity in humans, which is very limited, and gave a report to the Department of Veterans Affairs (VA) as required by law, the Persian Gulf War Veterans Act of 1998. [see Federal Register, July 6, 2001, Volume 66, number 130, pages 35702-35710]. The NAS generally found that the evidence to clearly implicate uranium as causing diseases in humans [my emphasis] was either lacking or not strong. The Secretary of the VA, Anthony Principi, determined that there was no association between uranium exposure and health effects. For example, the NAS referred to one study in which there was an individual with high accidental inhalation of uranium who experienced transient gastrointestinal distress. In the accident, one individual with dermal (skin) exposure had no gastrointestinal effects. "Accordingly, the Secretary [of the VA] has determined that the credible evidence against an association between gastrointestinal disease and uranium exposure outweighs the credible evidence for such an association, and has determined that a positive association does not exist."
 

Adverse Health Effects Associated with Gulf War Syndrome*

Reactive airway disease, respiratory problems, lung cancer

Kidney failure, chronic kidney pain and kidney stones

Neurological abnormalities - short and long term memory deficit, neuropsychological disorders

Immune dysfunction - supression of immune system

Vision degradation and night vision loss

Skin rashes and skin cancer

Wide range of cancers - lymphoma, leukemia, lung, liver, breast, gastrointestinal

Sexual dysfunction and cancer of sex organs - testicles, ovaries and uterus

Birth defects in offspring due to chromosomal damage in gametes (sperm and egg)
 

*These adverse effects are reported by Dr. Doug Rokke, a health physicist with first hand experience from military clean up operations following the Gulf War in 1991. For further information see: http://www.iacenter.org/depleted/duupdate.htm
 
 
 

Conclusions Regarding Depleted Uranium Toxicity

Some health physicists feel that depleted uranium (DU) does not appear to have significant risk to health as a result of its radioactivity, even if significant amounts are ingested or inhaled. Others would argue that any increase in levels of exposure to radiation will necessarily increase one's risk to cancer and other health effects.

Uranium, including DU, is a chemical toxin known to cause chromosomal abnormalities, genetic mutations, damage to renal tubules (kidney), neurological impairment, transformation of human cells to cancerous phenotypes, reproductive impairment, and developmental abnormalities. Many of these effects were shown in laboratory animals and have not been conclusively shown to occur in humans. Naturally, there are ethical considerations regarding experimental exposure of humans to substances known to be toxic to mammals.

These known chemical toxicity effects of uranium could account for many of the symptoms associated with Gulf War Syndrome in veterans. This does not "prove" that DU causes Gulf War Syndrome, but certainly implicates DU as a toxic substance if people are exposed to significant levels of DU dust that would be present in and around a field of battle where DU weapons are used. The DU dust from burning DU could remain in the area for many years, being resuspended in the air by movement of vehicles, animals and people in the area.

There has been a reported high incidence of birth defects and cancers, especially childhood cancers in Southern Iraq in recent years. The World Health Organization began an in-depth study in August 2001 to determine whether Iraq's claims that adverse health effects were due to the depleted uranium used by US and coalition forces in the 1991 conflict. In November 2001, after strong U.S. lobbying, the U.N. General Assembly voted against continuing the U.N. backed study in Iraq [the vote was 54 to stop, 45 to continue and 45 abstentions]. The U.S. delegation was reported to have lobbied very strongly to stop the study in Iraq.
 

Conflicting Governmental Policy

"If DU enters the body, it has the potential to generate significant medical consequences." Army Environmental Policy Institute, 1996.

"...it is unlikely that health effect reports by Gulf War veterans today are the result of exposure to depleted uranium in the Gulf war." Presidential Advisory Committee on Gulf War Veterans' Illnesses, January 1997.
 

Final Note

Most official investigations into the health effects of uranium on humans refer to epidemiologic studies of health effects on workers in the uranium industries since the 1940s. Most studies found that uranium industry workers had no greater risk of cancers or other health problems than the general population. One must keep in mind that the health hazards of radiation from radioactive materials was well known at the time the uranium industry was getting started. The industry built in safeguards against excessive exposure of workers in order to prevent any public outcry against the industry. There was probably also closer screening of the health of workers entering the uranium industry relative to many other industries in the mid-20th century. Other than the few cases of serious accidents and the ill health of miners, which is not unique to uranium mining, the uranium industries have received a relatively clean bill of health. This has been the main argument used by the U.S. Government against implicating depleted uranium as a cause of Gulf War Syndrome and the increased cancers and birth defects observed in the population of Southern Iraq after the 1991 Gulf War.

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