Panel discussion in the United Nations on October 26, 1999 sponsored by the NGO Committee on Disarmament, in cooperation with the UN Department for Disarmament Affairs.

PANELISTS:
DAMCIO LOPEZ, Depleted Uranium Study Group, Re-Visioning New Mexico
COLONEL ERIC DAXON, Ph.D., U.S. Army Medical Command
HARI SHARMA, President, Radiation Environmental Management Systems, and Professor Emeritus, University of Waterloo, Canada
STEVEN FETTER, University of Maryland, College Park
DAN FAHEY, Military Toxics Project
APPENDICES submitted by Dr. Sharma

ROGER SMITH, Network Coordinator, NGO Committee on Disarmament:..We have a distinguished panel this afternoon to speak on the subject of "Depleted Uranium Weaponry: Technical and Political Aspects." This is an issue that is emerging. It is not prominent on the UN's agenda, but it relates to a form of weaponry which is now in active use. It was used both in the Persian Gulf War and in the Bosnia and Kosovo operations of NATO. Recently the UN's interagency Balkan Task Force, which was organized by the UN Environment Programme and the UN Committee on Human Settlements, Habitat, released a report of its field mission=s examination of the effect of the Kosovo operation on the environment and human settlements in Serbia. One of the aspects of that report related to the use of depleted uranium in the conflict. I will read briefly from the press release issued by the UN Environment Programme on the day the report was released.

DAMACIO LOPEZ: Thank you very much. The first thing we need to do is give you an idea of what depleted uranium is. When people hear the words depleted uranium, they obviously think it is a metal that has been depleted of the uranium. Nothing could be farther from the truth. What we are talking about here today is weapons made out of radioactive waste.

I am going to go back into the cycle to explain how depleted uranium comes about. Uranium is in veins in the ground, just as gold is. It is found with a Geiger counter because it is radioactive, it gives off energy. Miners go into these areas and remove the vein of uranium. Then the uranium is taken to a nearby site where it is milled. The milling process is to separate the impurities from the uranium. You end up with two piles. One has the uranium tailings, and the other has the concentrated, pure, uranium. The nuclear industry refers to this pure uranium as "yellow-cake." Scientists refer to this uranium as natural uranium. At this point, this natural uranium is put in box cars on trains or large trucks and it is taken to a facility where it is processed. The process is called the gaseous diffusion process.

There are three such sites in the United States, one in Oak Ridge, Tennessee, one in Paducah, Kentucky and one in Portsmouth, Ohio. At these sites there is an effort to remove as much of the high-level radioactive isotope U-235 as possible from the natural uranium or yellow-cake. The high-level radioactive isotope U-235 makes up less than one percent of the total amount of the natural uranium in the boxcar. U-238, the low-level radioactive isotope makes up over 99% of the natural uranium in that boxcar. Through the gaseous diffusion process they are able to remove more than 60% of the U-235 from the natural uranium, leaving behind less than 0.2% of the U-235 with the U-238 which is now referred to as depleted uranium, no longer natural uranium. There has been a change in the mix of isotopes.

They take U-235, the enriched uranium that has been extracted through the gaseous diffusion process, and send it to nuclear power plants to make nuclear fuel rods or to weapons laboratories to make nuclear weapons. The remainder of the natural uranium is a large amount. Only one half of one percent was taken out of the boxcar in the form of the uranium isotope U-235. The rest is called depleted uranium. Well, it is not depleted of uranium, obviously that is a misnomer. What it is depleted of, to some degree, is its radioactivity. But it is not depleted of its entire radioactivity. Therefore the depleted uranium is more than half as radioactive as it was when it was in its purest state as natural uranium (yellow-cake). This is very important to remember. The radioactivity is not minuscule.

Ever since the Manhattan Project, there has been a growing mountain of this depleted uranium that has contaminated many sites. People have not known what to do with it. Over the last 50 years people have dug trenches, and put the stuff in the ground, or sent it to the state of Nevada to a central depository underground. This generation of depleted uranium waste has been ongoing.

In the 1960s the US military decided to do something with this depleted uranium, that they could put it to use for military purposes. They knew about what Nazi Germany had done with uranium (not depleted uranium). In 1943 Nazi Germany used 1200 metric tons of uranium to make solid core ammunition. They had run out of wolframite. They had been holding back this 1200 metric tons of uranium to build a bomb. When they found out the United States was about to build the atomic bomb, they used their stockpile of uranium as bullets against the opposing forces. Most governments in the world have known that uranium could be made into weapons, because uranium is extremely heavy.

There is only one other metal as heavy as depleted uranium or uranium. That is tungsten. However, tungsten is expensive, whereas depleted uranium, which has been growing in piles since the Manhattan Project, is given away. The Department of Energy gives it to defense contractors, manufacturers and others who wish to use it for various purposes. Depleted uranium is very heavy and it is also pyrophoric, it burns, another advantage when using it as a tank penetrator. (They use it for many other purposes, such as ballast and on nose cones on some cruise missiles. I think it is time that the US government admits that depleted uranium was in some of the cruise missiles fired in Iraq and Yugoslavia in the nose cone and ballast.)

To make a penetrator, they mold a rod out of depleted uranium, and that rod is basically the bullet inside the chamber, inside the casing. When it comes out of the cannon of either a gun or a big tank it is coming out as a slug of uranium. This is not carbon steel that has been hardened with uranium, this is not a projectile that has a sheathing of uranium, or a pin rod through the middle of it. It is pure uranium with the misnomer "depleted uranium."

When the penetrator strikes the target it will have what appears to be an explosion. There are no explosives in the slug of depleted uranium. It is the mass and speed and the energy from the radioactivity that gives the impression of an explosion. The projectile is referred to as a kinetic energy penetrator. The penetrator then begins to burn through the metal. The metal is very thick in armored tanks. It burns through like molten metal, and as it burns it is giving off smoke.

The particles in that smoke are very tiny, somewhere between 1 and 5 micrometers in size. 30% to 70% of the slug of depleted uranium goes up as smoke into the air, and is taken by winds. In the Gulf War, we hit 5,000 Iraqi tanks. When the troops came in behind our tanks the radioactivity was raining down on them. This was the smoke that went up into the air. It comes back down, and the particles are of a very small size, small enough so they can be inhaled into the deep lung, and it also goes into the GI track. This is how the depleted uranium gets into the body.

Radioactivity and heavy metals are the two contaminants that can enter the body when depleted uranium burns. This is the combination that our troops and civilians faced in Iraq. The same was true in Bosnia and other sites where cruise missiles and other weapons containing depleted uranium have been used, tested and developed. Depleted uranium is almost impossible to clean up. The military and the government say the best they can do is to remove (clean-up) 30% of the depleted uranium contamination. They may pick up some of the shrapnel that falls on the ground and the surrounding soil. The half-life of depleted uranium, which is made up almost entirely of the low-level radioactive isotope U-238, is 4.5 billion years. I hope this has been helpful. Thank you.

ROGER SMITH: The next speaker is Colonel Eric Daxon. Dr. Daxon comes to us from the office of the US Army Medical Command in San Antonio, Texas. He also works with the office of the US Army Surgeon General. Dr. Daxon received his MA in nuclear engineering from MIT, and his Ph.D. in radiological hygiene from the University of Pittsburgh. He is a certified health physicist, has been referred to as the Pentagon's expert on depleted uranium and was the team leader of the research effort on depleted uranium conducted by the Armed Forces Radio-biological Research Institute. Colonel Daxon.

COLONEL ERIC DAXON: Good afternoon. My purpose is to provide a brief summary of the extensive work that has been done by the US Department of Defense to characterize the health and environmental effects of the military use of depleted uranium. I am concerned because there have been many alarming statements made concerning depleted uranium that are not supported by the science today. Science does not support the contention that depleted uranium is a weapon of mass destruction. Science does not support the contention that the use of depleted uranium will result in an environmental catastrophe.

We are using depleted uranium because it is the most effective material for these applications and it is relatively safe when compared to alternative materials. One of my objectives is to outline the science that basically supports these conclusions. I want to make a couple of quick points.

First, the explosion is not due to the radioactivity of the depleted uranium. When the penetrator hits a vehicle and gets inside the vehicle, you see an explosion as the penetrator reacts with the munitions and the fuel inside the vehicle. When it first hits you see something that looks like a sparkler. That is the pyrophoric nature of the depleted uranium. It self-ignites when exposed to high temperatures and high pressures. The primary reason that we are using these is that they basically self-destruct as they penetrate armor. A tungsten penetrator becomes blunt. A depleted uranium penetrator will become sharper as it is penetrating armor, and that is the primary reason that we are using it, along with its density. The self-sharpening effect gives it a significant tactical advantage.

Uranium is not a new substance. It is something that you are all exposed to right now. All of you have small amounts of uranium in your body. It is in the water you drink, and the air that you breath, and the soil. If you walk through a dusty area there is natural uranium in the soil in that dusty area. So there is roughly 90 micrograms, which is a small amount, of uranium in your body. It is called depleted uranium because it is depleted of Uranium 235. It is 40% less radioactive than natural uranium because the U-235 has been taken out of the uranium. What remains is U-238. Chemically, depleted uranium is the same as natural uranium, but it is 40% less radioactive.

The health effects of uranium have been studied since the 1940s. There has been an enormous effort to study the health effects of uranium when this became a part of the Manhattan Project. It has been studied in animals, and we have done epidemiological studies of uranium workers. A tremendous amount of work has been done studying the health effects of uranium and depleted uranium. Basically they are the same, only depleted uranium is 40% less radioactive. So we have done a lot of work, and by we, I mean the international community. This is not just US work.

All of this work shows clearly that the health effects are dependent upon the amount that actually gets into the body. A lot of the more alarming statements talk about the measurement of depleted uranium. The fact that you can measure it does not necessarily mean that it is a hazard. It is the amount that actually gets into the body that constitutes the hazard.

The US, using non-DOD and DOD research laboratories, has been studying the health effects of depleted uranium since the early seventies. Our studies are basically focused on trying to determine the amount. Mr. Lopez talked about the aerosol. We are measuring the aerosols around the targets when they are struck. We are measuring the aerosols around depleted uranium when it burns and inside the vehicle when it burns. We have made a relatively extensive effort since the 1970s to characterize the amount, because that is where the health hazard is, the amount of depleted uranium that is internalized in the body and available to be distributed in the environment.

It is not sufficient to say there is a lot of uranium. You have to measure the amount in the body. The studies that we have done of the aerosols have shown that only the personnel in the vehicles at the time the vehicles are penetrated could receive doses that exceed the occupational safety standards, those that are in, on or near these vehicles at the time they are penetrated by depleted uranium. In all other situations, our studies show that the exposures are below the occupational standards. There is no other group that might start approaching occupation standards except those inside the vehicle when the vehicle is contaminated, which is a confined space.

Key documents have reviewed all of the data that is available on the health effects. The first is a study by the US National Academy of Sciences, Biological Effects of Ionizing Radiation. It is an excellent compendium of the health effects of depleted uranium. The Agency for Toxic Substances and Disease Registry is part of our Centers for Disease Control. It has an excellent compendium, and there are many others that have reviewed the effects. In all cases these health effects are related to the amount in the body.

In terms of the efficacy of use, this has been reviewed several times. In the 1970s the National Materials Advisory Board reviewed the efficacy of uranium from a health and environmental perspective. Then it was reviewed again. There were five reviews done by the US DOD committees. In 1974 the GCTD committee that reviewed this said significant amounts of depleted uranium may be available during a battle. The battle they were talking about would have been the Russians coming through the Fulda Gap. I have talked to the author of that report. It was predicated on many troops coming through a confined area, and their definition of significant was above peacetime levels.

The most recent review was by RAND, and I would like to ask Dr. Naomi Harley, who was one of the authors of the RAND report, to talk about it.

DR. NAOMI HARLEY: Thank you, Colonel Daxon. I work at 34th Street on First Avenue, at NYU Medical School, so I am a neighbor to the UN. I have been working with natural uranium radioactivity, dosimetry and risk, for about 40 years. Natural radioactivity and radiation has been my main career path. Recently, working on the RAND Report, I started looking at all of the epidemiology studies of uranium exposure. Epidemiology is the study of health effects related to exposure, and in this case uranium exposure.

Many workers have been exposed to high air concentrations of uranium. When uranium is taken from the ground, first you have miners underground, extracting ore from tunnels and exposed to the natural ore dust and radon gas. Then the ore goes to a mill, where millers crush and grind the ore and perform the first extraction of uranium. This is shipped to other sites where chemical processing takes place to separate the uranium from the other elements in the ore. In this step various compounds of uranium are produced that workers are exposed to. Finally you have the extraction of the U-235 and some U-234 from natural uranium that originally contained the three isotopes, U-238, U-235, and U-234. This last separation step was performed at Oak Ridge, Tennessee by gaseous diffusion. It is the U-235 that is used for reactors and weapons. The residual uranium, after extraction of the U-235, is called depleted uranium, that is, it is depleted of U-235. Thus, depleted uranium is less radioactive than the natural form and is about half as radioactive as the original natural uranium.

The US has a history of problems with radioactivity, going back to the women who painted radium dials in the 1920's. These women developed bone cancer because they had very serious ingestion exposures. Radium was painted onto watch faces and instrument dials by dipping a fine brush into radium paint, and then putting a fine tip on the brush by putting it in the mouth. These workers had enormous radiation exposures. Following this experience, the US has always been very sensitive to radiation and radioactivity exposure, and monitoring of radiation workers following the radium dial painter deaths, has always taken place. There is no other industry that can claim to have personal exposure assessment as the industry surrounding the handling of radioactive materials. Therefore, the people who worked in the uranium industry, the mines, mills, chemical processing plants, and gaseous diffusion installation were monitored for exposure.

There are a few epidemiological studies I would like to cover to show the extent of worker exposure in the uranium industry, and the search over the years for any health effects.

Overhead 1: Oak Ridge, TN – Cohort Study (1943-1947)
U Conversion and Enrichment Plant
 

Plant                                                         Oak Ridge (Y-12)

Persons                                                     18869

Levels                                                       Mean Air – 300 ug/m3
                                                                  Urine 33%
                                                                  >50 ug/L

Comp.                                                         UO2,UC14,UF6,UF2O2,UO3,UO4,UF4
                                                                    <97% enriched

Follow Up                                                     32-36 Y

Find                                                             Fewer than Exp. Deaths, No Other

Polednak, Frome J. Occ. Med. 1981
 

Overhead 2: Occupational U Exposure (4 Studies)

(Fuel Fabrication, U Mills, Gas Diffusion, U Metal)
 
 

Plant     United Nuclear, CT     U Mills (7), CO     Portsmouth, OH     Fernald, OH

Persons         4106                     2002                     5773                         146

Levels                                                                 Urine 0.6%                 >5000
                                                                            10-200 ug/L             dpm/100 cm2
                                                                                                                Urine <15
                                                                                                                    Ug/L

Comp.         UF6, U                 U, Th, Ra             UF6, UO2F2             Ore, U3O8
                    Enrich.                                                 90% Enrich.          UO3,UF4,U
                                                                                                                    >10%
                                                                                                                Enrich, DU

Follow Up     1-23Y                 6-37 Y                     1-28 Y                     10-34 Y

Find         Deficit                 Deficit                     Not                             Poss.
                Deaths                 Deaths                 Significant             Shortness Breath
 

1. Hadjimichael et al. 1983, 2. Waxweiler et al. 1983, 3. Brown, Bloom 1987, 4. Niosh 1987

The largest follow up epidemiological study was done on workers at Oak Ridge, Tennessee. Workers from 1943 to 1947 were monitored. In the Oak Ridge Study there were 18,869 people followed for health effects for up to 36 years. The monitoring consisted of measuring air concentrations of uranium, and urine, measured for uranium excretion. A fraction of any uranium inhaled or ingested will be excreted in urine, and this is a very sensitive test for actually having uranium in the body. During this time, workers breathed a mean air concentration of 300 micrograms uranium per cubic

meter, that is 0.3 milligrams per cubic meter. This is a significant exposure. In the early days, these workers were trying to produce enough uranium to make a weapon. The average urine excretion was 50 micrograms per liter. This value is almost twice as high as Gulf War veterans are excreting today, who have uranium embedded from shrapnel wounds.

Overhead 1: The Oak Ridge Study of 18,869 workers. Look at the variety of compounds these people were exposed to. There is UO2, UO3, UF6 etc., in all, both soluble and insoluble compounds. The Oak Ridge workers were also processing enriched uranium, so they had a higher radiation exposure as well as the chemical factors from uranium compounds. These workers have been followed for up to 36 years. What was found? There were fewer than expected deaths, and no other health problems. There were fewer deaths because of the healthy worker effect. That is, these people were generally healthy, and employed occupationally in the industry. Everybody eventually dies, but as of 36 years of follow up, fewer died compared with the expected number of deaths.

Overhead 2: Four other large epidemiological studies. There are 16 follow up studies in all in the US, and one in Britain. The studies shown in these two overheads report on a total, of about 30,000 people. There are 18,869 people at Oak Ridge, 4,000 at United Nuclear, 2,000 in the Colorado mills, and almost 6,000 in the Portsmouth study. In the Niosh study at Fernald, there was exposure to depleted uranium. In all of the studies, there has been no adverse health effects, even with long-term follow up. In Fernald they found there is a possibility that a few people had shortness of breath, because of their exposure to fluoride compounds.

Thus, there is a lot of history of workers with exposure to uranium. There are a tremendous number of people that have been followed for years to detect any health effects. There have been industrial exposures that have been quite enormous, from accidents, etc. Nobody has seen a significant health effect to date. Thank you.

COLONEL ERIC DAXON: The statements that Dr. Harley made are available in the RAND report on depleted uranium, which is also available over the web. Dr. Naomi Harley can be reached at the New York University School of Medicine, Dept. of Environmental Medicine, 550 First Avenue, New York, NY 10016

ROGER SMITH: Our next speaker is Dr. Hari Sharma. Dr. Sharma has had a long and distinguished career in the field of radio-chemistry . He is professor emeritus of chemistry at the University of Waterloo, Canada. He studied chemistry and physics in India, and received his Ph.D in nuclear chemistry from the University of California at Berkeley. For more than ten years he worked in the Atomic Energy Establishment in Trombay, India as a research officer and finally as head of the Radio-chemistry and Isotope Division. Dr. Sharma is also presently the President of the Radiation Environmental Management Systems Inc at Waterloo. Dr. Sharma.

HARI SHARMA: Thank you. Panelists, ladies and gentlemen. I believe in realities. My involvement with the depleted uranium (DU) issue came about quite accidentally. An organization, the Military Toxics Project, contacted me last year through Dr. Bertell, a member of the Order of Grey Nuns.

At a symposium, organized by the Military Toxics Project, that Dr. Bertell and I think, Mr. Lopez attended - I wasn't there - the task of getting analysis done for depleted uranium in urine specimens was assigned to Dr. Bertell. It is quite a simple task. I can say this to you as an analyst. I am a radio-chemist who has practiced his craft for fifty years. And I like to produce the best analytical results I can. I am not interested in the political aspects connected with DU.

Previous speakers have already described the radioactive properties of DU and, of course, it emits energetic alpha particles. In short DU, or uranium, falls under the category of radioactive materials. This is a reality. All I care is that radioactivity should be treated with the care and respect it deserves, so that it will not hurt us. Use of radioactive materials has provided immense benefits to mankind, but if they are dispersed, they cause harm and impart radiation insult. Even the discoverer of radioactivity, Mme. Curie, suffered from exposure to radiation. She had burns on her hands. So it takes its revenge if you don't treat it properly. If you disperse it in the environment, one way or the other it will harm people. I learned during the course of my professional career that people should not disperse radioactive materials in the environment. And that is why I am here to spread this message.

Urine samples were sent to me by Dr. Bertell to be analyzed for DU. I had done similar work for some workers employed in plants dealing with enriched or depleted or natural uranium in Oak Ridge, Tennessee, Paducah, Kentucky and in Fernald, near Cincinnati in Ohio where I found depleted uranium, or enriched uranium, connected with occupational exposure. In other words, presence of the type of uranium in their urine specimens could be related to exposure to uranium in the work place. Based on the results of the type of uranium in urine and tissue samples, the workers or their widows did get some compensation. A story was written about Joe Harding, who was allegedly exposed to uranium hexafluoride, in the Washington Post recently. That particular project was undertaken by me at the behest of a lawyer. I was not paid even the full laboratory costs of the analysis. However, I conducted the analysis because I had the resources for doing it. The irradiation facility was available at the McMaster University for performing the analysis. Dr. Bertell was familiar with my work. So she recommended that I analyze the urine samples and see if I could identify depleted uranium in urine specimens from the Gulf War veterans.

I thought the task could be performed easily because eight years had gone by, and the uranium that was inhaled or ingested by the veterans would not be present in their urine specimens. The biological half life of uranium is very short. It is twelve hours. Within a week it is completely flushed out of the human system, provided uranium compounds are of soluble type. So I thought I would do this task to sort out this mystery in a very short time, i.e., send the samples for irradiation and if I didn't find any uranium in the specimens, that would be the end of the task.

Well, the task did not finish there. As a matter of fact, I found that there was evidence of the presence of depleted uranium in the urine samples. Ladies and gentlemen, this is a reality. The question then arises, where is it coming from? It must come from a person's body. I analyzed in the initial stage about a dozen samples sent to me; and all of them seemed to indicate that there was depleted uranium still in the body. (Table 1).

Specimen                     U-235 Content                     U-238 Content                     Ratio
Code & No.                    nanogram (1 billionth    microgram, (1 millionth    U-238/U-235 of a gram)
                                    of a gram) per liter                   of a gram) per liter
_________________________________________________________________________________

M1                                 6.53                                 1.4                                         214
                                        8.70                                2.0                                         230
                                        4.35                                 <2.0                                     <430
                                        5.81                                 <2.0                                     <345
______________________________________________________________________________

M2                                 5.81                                 2.0                                         345
                                        7.25                                 2.0                                         276
                                        2.17                                 <2.0                                     <900
                                        2.90                                 <2.0                                     <690
______________________________________________________________________________

M3                                <5.                                     1+/-1                                 >200
                                                                                                                            229.8*
_______________________________________________________________________________

M4                             6.53                                     3.0                                         <459
                                    4.15                                     3.0                                         ~700
                                                                                195*
____________________________________________________________________________

M5                             10.15                                     3.0                                         295
                                    5.81                                     3.0                                             517
                                                                                                                                352*
____________________________________________________________________________

M6                             2.75                                     2.2                                             786
                                    5.1                                     <2.0                                         <394
                                                                                                                                242*
____________________________________________________________________________
*Mass spectrometric results -- accuracy is within plus-minus 5.

How do we analyze for DU? I think first I should indicate how the analysis is performed. We have the three isotopes in uranium (U) found in nature, namely U-234, U-235 and U-238; and so we can determine the isotopic ratio of Uranium 238 to Uranium 235. It is a fixed ratio (137.8) in uranium from natural sources. And I think both Mr. Lopez and Col. Daxon indicated that we have an intake of uranium in our body. We have to distinguish the two kinds of uranium, i.e. uranium from natural sources and ingested uranium as DU. This can only be done if you determine the isotopic ratio. I have looked for the two kinds of uranium in the urine specimens in my laboratory.

So far, to the best of our knowledge, there is no report that indicates that any effort was devoted for the determination quantitatively, the amount of DU in either the urine specimens or tissue samples from the Gulf War veterans; or even if some effort was made, they did not report DU in open literature.

Well, this is the key to the whole thing. If you do find DU in the urine specimens now at this time, DU must be stored in a body compartment and is being excreted with a long biological half life. A literature survey was made and we found a report which was issued by the Canadian Atomic Energy Control Board. In that report, it was indicated that the biological half life in the initial stage of ingestion is three days, then it is 280 days, then it is 800 days followed by ten years, or 3,500 days. Well if we analyze after eight years that means we are working with excretion rates close to 800 days and ten years biological half life. Ladies and gentlemen, this is a reality we must accept.

If this depleted uranium that was ingested or inhaled by the veterans during the conflict in 1991 only, it must have stayed inside the body for over eight years, and must have deposited radiation dose. The only compartment it is known to stay in is the lungs and lymph nodes.

I have analytical results of urine specimens from about 50 veterans. I have some urine samples from Iraqi civilians as well. Civilians from Basra have shown the presence of depleted uranium in their urine specimens. Now eight or nine years have passed, and if DU is still being excreted, that implies that DU is in their body, and it is still depositing radiation dose (see Appendices for the evaluation of radiation dose).

We have a concept in the area of radiation that if we take a thousand persons and expose them to radiation dose of one sievert (a unit of radiation dose), about 9% of the exposed population will suffer from fatal cancer, and die (see the last appendix for calculations). This is a well documented concept and this has been suggested by both the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) and the International Commission of Radiation Protection (ICRP). So one can easily calculate the number of persons who will be suffering from fatal cancer if one knows the radiation dose that has been deposited.

I have performed such calculations from the scanty data I have collected. One factor, the biological half life, is not yet certain and needs to be determined. Now ICRP, publication number 66, lists that the biological half life can be as high as twenty years. And I suspect from my limited experimental data that it might be twenty years. In that case we can evaluate exactly how many persons will suffer from fatal cancers and die. I think everyone knows that cancer is an insidious disease. It is not something one would relish suffering from. I think we must avoid exposing the civilian population as well to such a nasty radioactive material. Ladies and gentlemen, these, to my mind, are the realities resulting from the use of DU in warfare. Thank you.

ROGER SMITH: Our next speaker is Steve Fetter. Dr. Fetter is Associate Professor in the School of Public Affairs at the University of Maryland at College Park. He received his Ph.D. in physics from the University of California at Berkeley. Dr. Fetter has written many articles and books on the subject of arms control, nuclear policy and verification, including Toward a Comprehensive Test Ban Treaty, and two books he co-authored, The Future of United States Nuclear Weapon Policy and The Nuclear Turning Point. His work on depleted uranium, co-authored with Frank von Hippel of Princeton University, will appear in forthcoming issues of The Bulletin of the Atomic Scientists and in Science and Global Security. Steve Fetter.

STEVEN FETTER: Thanks. I am not an expert on depleted uranium. I got working on this because in May I was at a meeting in another country and a former Ambassador to the UN said that the United States was using radiological weapons in Yugoslavia and had used radiological weapons in Iraq. That estimates were that half a million people would die as a consequence. I thought that this was alarming, whether it was true, or whether it wasn=t. If it is true it is certainly a scandal, and if it is not true it is alarming that a former Ambassador to the UN would be saying this. When I returned I decided to investigate this. I have experience evaluating the risks of other releases of radioactivity. Frank von Hippel had had a similar experience, so we decided to work together. The work that I will present today is ours, on the health risks of depleted uranium.

Environmental Effects
Uranium is ubiquitous in the environment
1-4 ppm in soil = 2-8 tons/km² in top m
3ppb in seawater = 3 tons/km³
Compare to <1 ton/km² for DU in battlefield areas
Natural uranium more radioactive than DU
Much of the DU not biologically accessible

First, if you don't have internal exposure to depleted uranium, if you don't ingest or inhale the uranium, it is fairly easy to calculate the health risks because they depend only on exposure to radiation. If you don't have contact with uranium with your bare skin, the only hazard is from gamma rays, or photons, and the maximum possible dose rate in that case is 2.5 millirems per hour. Millirems probably don't mean much. Inside a tank fully loaded with DU munitions the dose rate is about .2 millirem per hour. If you stand above a heavily contaminated battlefield, and heavily contaminated would be about 1 ton of depleted uranium per square kilometer, then the dose rate is about 1 millirem per year. You can compare this to the occupational standard, 5 rem per year, and to the natural background dose. The natural background dose is about 300 millirems per year. So the dose rate from exposure to ground contaminated by depleted uranium is quite small.

If you pick up a piece of depleted uranium scrap lying on the ground, then there is the additional hazard of beta particles that will irradiate the skin. In that case the dose rate is much higher, about 100 times higher. The dose rate exceeds occupational standards by about a factor of nine also. So it is a hazard to pick up bare uranium and put it in your pocket, or make a bracelet out of it and wear it. But nevertheless it is not a catastrophic occurrence. Even if you did make a bracelet out of depleted uranium and wore it for a year, it would increase the chance of skin cancer by about one percent. Those are cancers that would only be fatal in a few percent of the cases. The risks from external exposure to an individual are rather minor, and that is true even if you add up that risk over an entire population. If I distribute 300 tons of uranium, which is about the amount used in the Gulf War, over an area with a population density of Iraq, the total exposure, the total population dose, would result in only about .1 cancer deaths, really a 10% chance of one cancer death.

Uranium is much more hazardous if it is inhaled or ingested, and much worse if inhaled and ingested. I will talk about the radiation and the heavy metal effects separately. Five rem is the permitted occupational dose in one year. In order to receive a dose of 5 rem, one would need to inhale about 100 milligrams of insoluble uranium to suffer any immediate, near-term health effects, radiation health effects. If you inhaled 40 grams of uranium there would be a risk from fibrosis long before radiation. The concern is much more that some of the uranium that you would inhale is soluble, and that that soluble uranium, because it is cleared from the lung much faster, would reach high concentrations in the kidney and be toxic to the kidney, much like other heavy metals. In that case, much lower doses can be hazardous, doses of 10 to 40 milligrams.

I am going to try to put this in perspective by showing the amounts that could be actually inhaled nearby. I should say first what the fractions of soluble uranium are. There are two kinds of events that could lead to the release of depleted uranium aerosols, the impacts of penetrators, and

                                                                          Impacts on hard targets     Fires

% converted to respirable aerosol                                 3-70%                 <0.05%
% aerosol in soluble form                                               15-45%                 3-7%

                                                                           Aerosols inhaled from
Radiation effect: cancer death                     <0.2% risk per 100mg
Renal Damage
transient                                                                         >20mg                 >100mg
permanent                                                                      >100mg               >500mg

fires. Fires convert very little of the depleted uranium into a respirable aerosol. Impacts, on the other hand, can convert a large fraction of the depleted uranium to an inhalable aerosol. Furthermore, a large fraction of that aerosol could be soluble, and pose these heavy metal risks. So, you can get an idea what sorts of exposures are necessary to pose a hazard. Basically, an exposure greater than 20 milligrams presents the risk of toxicity to the kidney, of transient or temporary toxicity. An inhaled dose of 100 milligrams would be much worse.

Internal Exposure Hazards:

    radiation (insoluble)
    heavy metal toxicity (soluble)
Inhalation worse than ingestion

                                                                                Inhalation     Ingestion
Radiation effects
5 rem                                                                     100 mgins      50,000 mgsol
respiratory impairment*                                  40,000mgsol
Renal damage
transient                                                                     8mgsol              80mgsol
Permanent                                                                 40mgsol         400mgsol
* 3000 rem to the lungs in one year

Bare skin in contact with bare DU
Dose to skin: 230rem/hr

External Exposure: Only health hazard is
If bare skin not in contact with bare DU
Theoretical maximum: 2.5 mrem/hr
Inside DU-loaded tank: 0.2 mrem/
Ground contaminated with 1 t/km² (1g/m²)
Ground near impact with 100 g/m²

Compare to:
Limit for unrestricted occupational access: 25 mrem/hr
Threshold for short-term health effects: 300,000 mrem (in 1-2 days)
Risk of skin cancer from DU bracelet: = 1% per year of exposure

Population dose:
If 300 tons of DU dispersed in area with population density of 50/km^2....^.......
...50-year dose = 200 person-rem
= 10% chance of 1 extra cancer death

Compare to:
Limit for unrestricted occupational access: 2.5 mrem/hr
Limit for public: 100 mrem/yr
Natural background: 300 mrem/yr
Occupational limit: 5000 mrem/yr
Risk of cancer death: 1 in 2,000,000 mrem

Now what are the doses? These are based on calculations, but they are in agreement with the

data of which I am aware. Basically, if you are outside a vehicle, then the exposure is quite low. One kilogram of depleted uranium released as an aerosol results in several different events: the impact of a penetrator, and fire. This is a logarithmic scale, so the maximum dose, even very close to the point of impact is about a factor of a hundred below the threshold for a toxic effect, and of course much further from the impact, several kilometers, it is much smaller. A soldier might have been exposed to aerosols from many impacts. A soldier exposed to almost every impact, directly downwind to almost every impact that occurred in the Gulf War, and still not reach an inhalation dose that would be required to produce known toxic effects.
 
 

Inside Struck Vehicles
During impact:
Inhaled dose could be > 50 mg
Dose from shrapnel below threshold for
toxic effects, but moderate radiation doses possible (few rem per gram).

Outside Struck Vehicles
Dose to nearby soldiers is low
Even very close to an impact or fire, doses are very low - factor of 50 to 1000
 below threshold for toxic effects
Even if an individual was 10 km downwind from the impact every round
used in the Gulf (or 1 km from 1% of these impacts), dose < 10 mg

After impact
Clean-up, repair without protective gear could result in very high doses
Rescuers, souvenir hunters, could inhale possibly worrisome amounts of DU
Best way to evaluate is a urine test soon after exposure. This was not done in the
Gulf, so difficult to determine how many were heavily exposed: tens? hundreds? more?

Dose to surrounding population is low:
If 30 tons respirable aerosol dispersed in area with pop. Density of 50/km²...
...50-year dose +4,000 person-rem
= 2 extra cancer deaths
Individual risk< 0.001%

As was mentioned earlier, if you are inside a vehicle, the situation is potentially much worse because air currents, wind, can't disperse the aerosol. In that case, high doses are possible. High doses may also be possible for soldiers who enter contaminated vehicles afterwards, either to rescue people or to clean up the vehicle, so it is important that any exposure to a contaminated vehicle be minimized. Clean up crews, for example, should be equipped with proper respiratory protection. Of course the best way to evaluate these exposures would have been to have done urine tests immediately after exposure. To my knowledge, those were not done, so it is hard to say how many people were in those categories and possibly received high exposures to uranium.

Our conclusions: We conclude that the risks of exposure to DU are very small, except for people in the following categories:

• People who were in struck vehicles, or
• People who entered struck vehicles subsequently to clean up the vehicles, or scavengers
• People who have continuous contact of bare skin with bare DU

Steps should still be taken to minimize exposure. For example, contaminated vehicles should be isolated from the public, soldiers should be trained to avoid any unnecessary contact with contaminated vehicles. The public should also be educated so that they do not pick up pieces of depleted uranium and fashion them into bracelets. Thank you.

ROGER SMITH: Our last speaker is Dan Fahey. He first encountered depleted uranium as a munition in the fall of 1990 while attending the Navy's Phalanx Close-in Weapon Systems School. After learning to fire nuclear Tomahawk cruise missiles Mr. Fahey applied for a discharge as a conscientious objector. In July, 1991 Mr. Fahey served briefly in the Persian Gulf before being honorably discharged. Since 1994 Dan Fahey has researched the role of depleted uranium in the health problems affecting more than 100,000 American Gulf War veterans. His early work attracted the attention of the Pentagon's Gulf War Illnesses Office which in 1997 threatened to file a lawsuit against Mr. Fahey. Mr. Fahey has authored numerous reports on depleted uranium weapons, including the 1998 Case Narrative on Depleted Uranium Exposures in the Gulf War. After six years of assisting Vietnam and Gulf War veterans with disability claims, Mr. Fahey recently started work as the national organizer on depleted uranium munitions for the Military Toxics Project, a non-governmental organization. Dan Fahey.

DAN FAHEY: Thank you. I hope to clear up some of the misconceptions that have been expressed. As was stated earlier, in the sixties and seventies the military was testing depleted uranium for use in kinetic energy penetrators. Essentially you are shooting a very dense piece of metal at a very high velocity. When it hits the target, such as a tank, it punches its way through. In 1974 the decision was made to switch from tungsten to depleted uranium. At that time the reason was not that DU worked better. The reason that they switched was because there were large quantities of depleted uranium which were available for free to the arms manufacturers. If you read the report, that is what it says.

The testing continued, and it contaminated communities in this country. It is a testament to the fact that it is a hazard that communities in Albany, New York, Concord, Massachusetts and near where Damacio lives in New Mexico have been cleaned up from the contamination. Literally tons of contaminated soil were removed and sent to Utah. Millions of dollars were spent. So this is recognized by our government as a hazard to communities in this country. By the time 1990 rolled around they had spent a lot of time perfecting the effectiveness of the weapon. I will read you a quote from an Army report, The Kinetic Energy Penetrator, Environmental and Health Considerations, of July 1990, written six months before Operation Desert Storm:

When the war ends, because there was no training, and no knowledge - (and I have to disagree with Mr. Lopez: 1991 was the first time that depleted uranium ammunition has been used) - you have literally tens of thousands of American troops going to the battlefield, climbing on equipment, in some cases as part of their combat operations, looking for souvenirs. Some of the contaminated American vehicles, that were hit in friendly fire incidents, were driven back to Saudi Arabia, and people were climbing all over this equipment. In my report, I have reports from the Pentagon's own interviews with veterans showing people climbed on and entered multiple contaminated vehicles. The dust was being stirred up, and some of the very people the Pentagon interviewed are having health problems. Was it related to depleted uranium? That is another question. But because we have no base line data, no testing was done after the Gulf War, we simply don't know how much depleted uranium veterans were exposed to.

After the Gulf War, when veterans started to come forward reporting health problems, the Pentagon ruled out depleted uranium. They said no, there is no way it is depleted uranium. For years they said there were only a few dozen exposed. Finally in January, 1998 we forced them to admit that thousands, their words, may have been exposed. But they did not say whether that meant 2,000 or 200,000. And last year they released a map showing the movement of every American division through those contaminated areas. After they admitted that large numbers may have been exposed, they moved back to the next line of defense, which we have heard here today: that no one was exposed to enough depleted uranium to cause any health problems.

The RAND Report, I believe, in the future will be largely discredited. There are a number of flaws in it, including the fact that they did not review a large number of peer-reviewed, published studies specific to depleted uranium, and that there is clear conflict of interest among at least two of the authors. One has been a long-time Department of Energy contractor. We know from the recent Washington Post stories about Paducah, the government has done a poor job protecting workers from uranium. Another one of the authors works for the Pentagon Gulf War Illness team, so right there is a bias in the people writing it. When you read the RAND Report you will see that while they do mention studies that acknowledge health effects of uranium, what they say, and what the Pentagon says, is no one was exposed to enough depleted uranium to cause any health problems. For several years I have been saying, and others have been saying, where is the data? How can you support that position, no one was exposed to enough? The fact is, they have nothing to back this up.

I am going to read to you from a letter, dated September 24, 1999. This is from Congressmen Lane Evans, Bob Fellner and Senator Russell Feingold, who have requested a General Accounting Office investigation on depleted uranium. And this investigation is not complete yet, but the GAO is already finding information significant enough that these Congressmen are acting on it. This is a letter to Secretary William Cohen, Secretary of Defense. I will just read you the first paragraph:

We don't need theoretical exposure estimates of how much depleted uranium is on the ground and the theoretical exposure to a person. I want to know if a child climbing on a tank and going inside it is at risk. If a veteran has to go into tanks to remove equipment and the tank is contaminated, is he going to be exposed to enough that is going to cause health problems? There are veterans who appear to have had heavy exposure to depleted uranium who are having health problems that may be consistent with this type of exposure.

The Armed Forces Radio-Biology Research Institute is doing studies on this based on their preliminary findings. They say we are concerned, and we want a lot more study on depleted uranium's relation to cancer, to immune system problems, to neurological disorders, male and female reproductive effects and birth defects. This is based on preliminary findings. I discussed them in my report.

What we have is a situation where we have, on one extreme, the Pentagon, which is so enamored of this weapon they do not want to admit there could be any problems associated with it. On the other extreme you have people who I believe have irresponsibly exaggerated the dangers involved here, the Yugoslav government being one of those. This spring they issued exaggerated claims saying regional catastrophe. What is missing is the middle ground. The middle ground is that the vehicles that are hit do pose a hazard to human health. If access is not restricted, people may climb on them. They may climb on multiple contaminated vehicles and they may be exposed to amounts of depleted uranium that can cause health problems.

I should mention that the Army's own research is finding that the radiation may not actually be the hazard. It is the chemical toxicity that may be causing the tumors in mice and other health effects. For years we have been saying, we need more research on this. And the Pentagon was saying, no we don't, because no one was exposed. It is really time that we had some objective investigation of this. We are very hopeful that the General Accounting Office is conducting such a review. But this is a weapon that is proliferating quickly. Our country has been selling it. Russia, Pakistan, France, UK, China and Iran now have it. It is going to be used in the conflicts in the next century. Battlefields are going to be contaminated. Civilians and soldiers are going to be exposed. I think it is in our best interest to fully understand the effects of this weapon before we continue to go forward with releasing, shooting, basically, a radioactive toxic waste. We are basically taking our garbage and dumping it in somebody else's backyard. Thank you.

APPENDICES: submitted by Hari Sharma

Introduction to Appendices A, B and C.

According to data gathered from various sources, during Gulf War in 1991 at least three hundred tons of depleted uranium (DU) was used by the USA and additional 59 tons by the UK. Twenty six percent of the projectiles found their targets whereas 76 per cent projectiles are presumably lying buried in sand. On hitting its target, DU catches fire and burns to oxides of uranium. Forty six per cent of this DU converts itself to depleted uranium dioxide aerosol (DUDA). Roughly, half of the aerosols are of respirable size. This gives 21.5 tonnes of DUDA in an area of 2400 square kilometers.

Assuming complete mixing in atmosphere up to 250 meters height gives the concentration of DUDA 35 micrograms per cubic meter. A person on active duty inhales 25 to 30 cubic meters per day, i.e. about 1 milligram of DUDA per day. For details of the calculation see Appendix A.

DUDA stays in the area for a long time. It has been found that it survived over two years in air in Kuwait city and most certainly in Basra as well [F. Bou-Rabee, Radiat. Isot. vol. 46, pp. 217-220, 1995].

Inhalation of aerosols in the war zone or near the war zone over extended periods resulted in accumulation of uranium dioxide in lungs. From there it is excreted via urine. Uranium dioxide formed at very high temperatures is a ceramic type Y insoluble compound and its excretion rate is very slow. The International Commission on Radiological Protection (publication 30, 31 and 66) suggests the biological half life (i.e. the time needed for 50 percent of the original amount of the substance to be excreted from the body) for uranium dioxide Class Y compounds as 500 days. It is now changed to 7,000 days. There is evidence to indicate that the biological half life of uranium dioxide produced at very high temperature is much longer. A Canadian study has suggested a short-term clearance component (half life 3 days) and three long-term clearances (half lives of approximately 280, 800 and 3500 days) under conditions of chronic, low level, exposure. For uranium dioxide aerosols produced at very high temperatures the half life can be as long as 20 years.

In a pilot study, several 24-hour urine samples were collected in 1999 from a number of Gulf War veterans. The samples were analyzed for isotopic ratio of uranium-235 (U-235) and uranium-238 (U-238) by the delayed-neutron counting and the neutron activation methods, and later by two other methods based on the use of a mass spectrometer. Measurements did confirm beyond any doubt the presence of DU in the samples, the average excreted amount was found to be 3 micrograms per 24 hours. For details see Appendix B.

In Table 1 below we calculate the whole body radiation dose in Sv for a person who in 1999, i.e. eight years after the contamination took place in 1991, has the excretion rate of 1 microgram per day, for various assumed biological half life values. For example, if the biological half life is 500 days, the present amount of DU in the person's body is 0.722 milligrams, the amount of the original intake is 41.4 milligrams, the equivalent whole body integrated dose is 0.192 sievert and the risk factor is 1.8 percent. For details of the calculation see Appendix C

Table 1.

Biological         DU in 1999         DU in 1991         Radiation Dose         Risk factor %
Half Life             milligrams             milligrams         whole body, Sv        (Fatal Cancer)

365 days                 0.523                 134.7                 0.15                         1.5
500 days                 0.722                 41.4                   0.064                       0.6
2.5 years                 1.318                 12.1                   0.034                       0.3
5.0 years                 2.636                  7.99                  0.045                       0.4
10.0 years               5.272                  9.18                  0.11                         1.0
20.0 years             10.544                 13.91                 0.26                         2.4
 

We see that depending on the biological half life, the risk factor for 1 microgram of DU excreted per day ranges from 0.3 percent for the 2.5 years half life to 2.4 percent for the 20 years half life. With 3 micrograms as the average value for the Gulf veterans, these numbers need to be multiplied by 3, giving the risk factor range from 1 percent to 7.2 percent. In other words, out of 100,000 veterans having the excretion rate of 3 micrograms per day now, it would appear that there will be additional fatal cancers ranging from 1,000 to 7,000.

Other radiation damages to humans (damage to the immune system, genetic defects etc) have not been considered. Effects from exposure to low-level long term radiation are not fully understood. Inhalation of uranium dioxide in lungs leads to exposure to such radiation and therefore we may not have full understanding of deleterious effects on human health.

Aerosols of uranium dioxide can travel a long distance. DU has been found in urine from residents of Basra who resided there in 1991-3. The excretion rate in a urine sample prepared by mixing urine from nine residents of Basra was found to be in the range about 2 microgram of DU per day. It can be seen that the civilian population of Basra has been exposed to radiation exposure through inhalation of uranium dioxide aerosols. Our calculation shows that additional several thousand per a hundred thousand persons exposed to depleted uranium in 1991-3 will suffer from fatal cancers. Indeed, it is evident that the incidence of cancer in Basra has increased several fold and it is our belief that, at least in part, exposure to depleted uranium has contributed to this calamity.

The information gathered so far through the analysis of urine samples convinces us that uranium dioxide produced by the use of uranium weapons finds its way in human lungs through inhalation. Presence of uranium dioxide in lungs in veterans and in the civilian population does put the exposed population to undue risk. It is therefore essential that the use of uranium weapons in warfare must be banned.
 
 

APPENDIX A: Environmental Impact on humans during the Gulf War
=====================================================================

Total amount of DU used is 300 + 59 = 359 tons. Twenty six percent were exploded. During the explosion, DU burns and 46 percent of it converts into DUDA, out of which a half is of respirable size. We now calculate that (* means multiplication, / means division):

The amount of aerosol of respirable size = 359*0.26*0.46*0.5 = 21.47 tons =21,470,000 grams = 21.47E6 grams

The area of the war zone was approximately 2400 kilometers squared. Assuming a complete mixing of aerosols in atmosphere over the war zone up to 250 meters height, we obtain:

Volume of air = 2400 km squared * 1,000,000 meter squared/km squared * 250 meters
= 600,000,000,000 cubic meters = 6E11 cubic meters

Concentration of aerosols in air over the war zone = 21.47E6/6E11 = 3.5E-5 grams per cubic meters = 35 microgram per cubic meter.

A person on active duty inhales 25 to 30 cubic meters per day, which means that the person inhales about 35 * 30 = 1050 micrograms per day = about 1 milligram per day. A person then may have inhaled about 90 milligrams of DUDA over 90 days in the war zone.

The concentration of aerosol may be higher at the ground level than at the higher elevations from the ground. Also, there is dispersion and hence a reduction of the concentration of aerosol. There are other factors like trapping of particles in the throat area etc. This is only a rough estimate to show that a person on active duty in the war zone or nearby may have accumulated some tens of milligrams of DUDA in his lungs through inhalation.

DUDA is a ceramic compound, highly insoluble, like silica. It will not contaminate water in an aquifer. There will be no intake by plants either. Therefore the human contamination is through inhaling, i.e. DUDA will initially accumulate in lungs.
 

APPENDIX B: Measurement of the DU content in urine

=====================================================================

In a pilot study, several 24-hour urine samples were collected from Gulf War veterans. The samples were analyzed for isotopic ratio of uranium-235 (U-235) and uranium-238 (U-238) by the delayed-neutron counting and the neutron activation methods and by the surface ionization mass spectrometric (SIMS) method.

On irradiation with thermal neutron, U-235 fissions, giving fission products and prompt neutrons. A few fission products decay by beta particle emission and neutrons. These fission products are called delayed-neutron emitters. U-235 is the only isotope of uranium among naturally occurring elements that has this unique property and therefore one can determine the amount U-235 in the sample with very good accuracy.

On irradiation with neutrons, U-238 forms uranium 239. It decays by emission of a beta particle and 74-keV gamma rays to neptunium-239, with a half life of 23 minutes. The gamma rays can be assayed with the help of a high resolution germanium detector and a pulse-height analyzer (a gamma-ray spectrometer). This is used to determine the amount of U-238 in the sample.

Uranium is naturally present in its SOLUBLE form in food and drinking water. This uranium (within "normal", naturally occurring amounts) is not dangerous because it is readily excreted and therefore does not accumulate in the body. The amount of this uranium present in the body at any one time is of the same order of magnitude as the amount excreted per day, which is micrograms. (We see from Table 1 in the main text that the amounts giving a significant risk are in milligrams, i.e. a thousand times higher.)

Both the natural and the depleted uranium are present in the sample. We are interested in the latter because it originates from the inhaled DUDA which is an INSOLUBLE ceramic compound and therefore accumulates in the body.

Knowing that the U-238 to U-235 ratio (the so-called isotope ratio) in natural uranium is 137.8 and that this ratio in DU as used in the Gulf War is 498, enables us to deduce the fraction of DU in the total uranium content in the sample.

Let IR be the ratio of U-235 to U-238 (i.e. the inverse isotope ratio), as measured in the sample. The inverse isotope ratio for natural uranium is IN = 1/137.8 = 0.00725, and for DU is ID = 1/498= 0.00201. The fraction F of DU in the total uranium content is then given by the formula:

F = (IN - IR)/(IN - ID) = (0.00725 - IR)/(0.00725 - 0.00201)

Total amount of DU in the sample is then obtained by multiplying the total amount of uranium as measured in the sample by F.

The measurement of the ratio of the two isotopes alone enables us to determine the presence or absence of depleted uranium in the sample. The ratio must be between 137.8 and 498. The nearer it is to 498 the more DU and the nearer to 137.8 the less DU is in the sample.

The isotopic ratios of the two isotopes in some samples was measured by two other methods based on the use of a mass spectrometer. Measurements did confirm beyond any doubt the presence of depleted uranium in the samples.
 

APPENDIX C: Evaluation of Radiation Dose

=====================================================================

C1. Radioactive properties of uranium

Natural uranium consists of three isotopes: U-238, U-235 and U-234, with abundancies 99.275, 0.72 and 0.054 percent respectively. Enriched uranium, as used as a fuel in nuclear reactors, has more than 2 percent of U-235 and a higher than the natural content of U-234. Depleted uranium has less than the natural contents of U-235 and U-234. In the Gulf War depleted uranium with 0.2 percent of U-235 and 0.0011 percent of U-234 was used.

All three isotopes are alpha radioactive, as follows.

U-238 alpha-decays (half time 4.47E9 years, energy 4.196 MeV) into thorium Th-234. Th-234 beta-decays (half time 24.1 days, energy 0.198 MeV) into protactinium Pa-234. Pa-234 beta-decays (half time 1.75 min, energy 2.229 MeV) into U-234.

U-234 alpha-decays (half time 2.446E5 years, energy 4.777 MeV) into thorium Th-230.

U-235 alpha-decays (half time 7.038E8 years, energy 4.598 MeV) into thorium Th-231. Th-231 beta-decays (half time 25.52 hours) into protactinium Pa-231.

Activity (or emission rate) of a radioactive source is measured in bequerels, i.e. the number of decays produced by 1 gram of the substance in 1 sec. Knowing the half time T and the atomic weight suffice for this number to be calculated:

B = (0.693/T) * number of atoms in one gram

For U-238 B is 12,429 Bq. For U-235 it is slightly greater because the decay half life is slightly less, but because the content of U-235 in DU is very small, its radioactivity can be neglected.

The decay half time of U-234 is much less than that of U-238, giving an activity 18,275 times that of U-238. In natural uranium the U-234 fraction is 0.000054, which when multiplied by the former number gives 0.987. This means that the alpha activity of one gram of natural uranium is roughly twice that of pure U-238, a half coming from U-238 and the other half coming from U-234. Obviously, in depleted uranium this contribution is smaller. Uranium used in the Gulf had only 20 percent of the natural content of U-234, which means the >>alpha activity of that uranium consisted of 12,429 alpha particles from U-238 plus roughly 20 percent of that number from U-234.

C2. Evaluation of the DU content in the body from excretion rate

Assumption: Excretion rate R(t) at any time t is proportional to the total amount A(t) of DU in the body at that time.

This assumption implies that A(t) will decrease with time exponentially, i.e.
A(t) = A(0) * exp[-0.693*t/t']

where A(0) is the amount at the time of contamination (t = 0), and t' is the half life, i.e. time needed for a half of the original quantity A(0) to be excreted. [When t=t', noting that 0.693 = ln 2, we have A(t')= A(0) * exp(-ln 2) = A(0)/2.]

The excretion rate is R(t) = (0.693/t')*A(t). If the excretion rate is known, A(t) is calculated as
A(t) = (t'/0.693) * R(t)
and the original amount taken in is
A(0) = A(t)*exp [0.693*t/t']

For example, if time of exposure is 1991 and time of measurement is 1999, the excretion rate R(t) = 1 microgram a day, and t' = 500 days, we have as follows.

t = 1999 - 1991 = 8 years.

A(t) = 500*1/0.693 = 721.5 micrograms

A(0) = 721.5exp[0.693*8*365.25/500]
= 41,293 micrograms
= 41.29 milligrams

We see that in order to calculate A(0), we need to know the biological half time. Unfortunately, this quantity is not known with a satisfactory degree of certainty. The ICRP suggests it to be from 500 to 7000 days. There is evidence that it may be much longer -- in fact as long as 20 years. In Table CT.1, we tabulate the corresponding amounts A(t) and A(0), assuming several biological half lives,
for the excretion rate R(t) = 1 microgram and t = 8 years.
 
 

TABLE CT.1

Biological                 DU in 1999                 DU in 1991
Half Life                     milligrams                     milligrams
(t')                             A(t)                                 A(0)

365 days                     0.523                           134.7
500 days                     0.722                             41.4
2.5 years                     1.318                             12.1
5.0 years                     2.636                             7.99
10.0 years                   5.272                             9.18
20.0 years                 10.544                            13.91
 
 

C3. Evaluation of Integrated Organ Radiation Dose.

The rate B of emission of alpha particles from 1 gram of U-238 is 12,429 particles a second, which makes 1.074 billion particles per day. Energy of such an alpha particle is 4.19 MeV, so we obtain

Energy emitted a day = 1.074E9*4.19*1.602E[-13]Joule/MeV
= 0.00072 Joule/day

We assume that DU is stored in lungs and all alpha particles dissipate their energy inside the lungs. The mass of human lungs is 1 kg, so we obtain for the daily absorbed radiation dose per gram of U-238.

Daily absorbed dose per gram of U-238 = deposited energy/mass
= 0.00072/1 = 0.00072 Gy/day
= 0.072 rad/day

In order to obtain the biological equivalent dose, the absorbed radiation dose must be multiplied by the quality factor for alpha particles in this energy range, which is 20. We obtain Daily biological dose per gram of U-238 = 0.00072*20 = 0.0144 Sv/day = 1.44 rem/day

If the amount of DU in the lungs stayed constant, we would calculate the total biological dose received during a certain interval of time simply by multiplying the above daily dose by the number of days and the amount of DU in grams. However, the initial quantity will exponentially decrease due to the excretion, so the total (or integrated) biological dose for the lungs will be

integrated dose = A(0) in grams * daily biological dose per gram* integral(from zero to tau) of exp[-0.693*t/t'] dt.
= A(0) in grams * dayly dose per gram * (t'/0.693) * [1 - exp[-693*tau/t']

where tau is the interval of time considered (or the so-called integration time). If tau is much greater than the biological half life t' the exponential in the last line can be neglected. (By "much greater" we mean "five times or more".)

For example if we take 500 days as the biological half life t', and tau = 50 years, for an initial quantity of 1 gram of U-238 we obtain integrated dose from 1 gram U-238 = 1*0.0144*500/0.693 = 10.4 Sv.

A Handbook on Health Physics gives a value of 3 Sv. The difference may be due to the fact that we are evaluating the dose assuming a simple exponential decrease of the initial DU amount. The excretion rate is complex in the initial stage. However it does follow the exponential law at a later stage. Initially, the excretion rate is at an enhanced level and therefore when the evaluation of the dose is based on the initial rate of excretion, the results obtained will be lower.

However we stress that we are dealing here not just with uranium dioxide, but with uranium dioxide produced at very high temperature. It is a ceramic compound, highly insoluble like silica. Its initial excretion rate may be complex but not necessarily enhanced. Also, we do not know the actual initial

amount A(0) of DU. We calculate it by using the measured excretion rate eight years after the exposure, extrapolating to zero time using the later stage half life. By neglecting the initial enhanced excretion rate, A(0) is obtained lower than it actually was, and therefore using our calculation procedure we are under-estimating, not over-estimating the integrated dose.

Energy deposition can similarly be evaluated for alpha particles emitted by U-234. The energy of alpha particle = 4.77 MeV. As shown in C1, the alpha particle emission rate for DU used in the Gulf conflict rate is one fifth of the rate of U-238. The energy deposition in the lungs from the decay of

U-234 in 1 gram of DU is therefore 0.2*1.074E9*4.77*1.602E[-13]Joule/MeV = 0.000164 Joule per day. This gives 0.000164/1 = 0.000164 Gy/day for the daily absorbed dose and 20*0.000164 = 0.00328 Sv/day for the daily biological dose.

For the 500 days half life we have Integrated organ dose from U-234 = 0.00328*500/0.693 = 2.4 Sv.

The total integrated radiation dose from the initial quantity of 1 gram of DU is a sum of the U-238 and U-234 contributions which for the 500 days half life makes 10.4 + 2.4 = 12.8 Sv.

From UNSCEAR for converting organ dose to the whole body whole dose the factor for lungs is 0.12 to 0.25. We take the lower one of the two figures as 0.12. Whole body radiation dose from 1 gram of DU for the 500 days half life is then 12.8*0.12 = 1.6 Sv.

One gram of DU is a huge quantity on a biological level. In Table C.2 we show the integrated radiation dose based on several assumed biological half lives, for the initial quantity of A(0) = 1 milligram of DU in the lungs. These values are obtained from those for 1 gram by simply dividing by 1000 ( for example 4.8 Sv above will become 0.0048 Sv). The integration time is taken to be tau = 50 years.

TABLE C.2

Biological Radiation Dose Radiation Dose

half life         lungs, in Sv       whole body, in Sv

365 days         0.0093         0.00112
500 days         0.0128         0.00155
2.5 years         0.0234         0.00280
5.0 years         0.0467         0.00562
10.0 years       0.0876         0.0106
20.0 years       0.1539         0.0186

Table 1 in the main text shows the values of the whole body radiation doses calculated on the basis of 1 microgram DU excreted a day. These values are obtained by multiplying the above numbers by A(0) from Table C.1, e.g. for the 500 days half life we have 0.00155*41.4 =

0.064 Sv, (or 6.4 rem).

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