Depleted Uranium Expert Shares Knowledge
WASHINGTON, January 3, 2000 (GulfLINK) - In the past year, many newspapers, magazines and Internet sites have featured information about the possible health effects of depleted uranium exposure. Recently, the CBS show "60 Minutes" covered this issue. Much of this information is conflicting, and reports seem to disagree on many important points. In an effort to clarify the facts, the office of the special assistant for Gulf War illnesses needed an independent scientist who was both highly qualified and able to explain scientific principles in layman's terms.
Naomi H. Harley is an authority on radiation physics. She earned her Ph.D. in radiological physics at New York University where she is currently a research professor at the University's School of Medicine, Department of Environmental Medicine. She has authored or co-authored more than 100 peer-reviewed journal articles on radiation exposure, measurement, and the risks of internal and external radiation exposure, with emphasis on natural background radiation. She has written six chapters in books dealing with radiation or toxicology and holds three patents for radiation measurement devices. She is a council member on the National Council on Radiation Protection and Measurements, an advisor to the United Nations Scientific Committee on the Effects of Atomic Radiation, and an editor of the journal "Environment International."
"I really feel that this is my life, my livelihood, my career. I've always been interested particularly in the health effects of radioactivity."
Harley says people who talk about the dangers of depleted uranium often don't realize how little its use affects the environment.
"Well, to begin with, most people don't realize that they live with an enormous amount of uranium already," Harley says. "All soil contains uranium. In normal soil, it's not unusual to find a ton of natural uranium per square kilometer." She agrees that in a battle zone much of the depleted uranium ammunition, which strikes hard targets such as tanks, will be dispersed in fine aerosol particles and settle over the ground.
"However, compared with Mother Nature," she says, "what you spread on the Earth's surface is almost indistinguishable from what was there already. This was certainly true in the Gulf War. There were follow up measurements made of soil in the battle areas and you really could not distinguish what's there normally from what was put there by the weapons."
In other words, she says these fine particles are mixed in with existing uranium without measurably increasing the amount present. And what about reports that before it settles, a cloud of aerosolized uranium could pose a danger to people who inhale particles miles away?
"Fortunately, it's really impossible to breathe in enough depleted uranium to do you any serious harm," Harley says. "If you work in an industry that uses uranium, you're allowed concentrations in the air of 0.2 of a milligram per cubic meter, which means in a work day you might inhale two milligrams. This is the kind of air concentration you find right near [an armored vehicle] where a DU round hits it. When you breathe it in, you breathe in some uranium, but the risk is so low it's very hard to calculate."
Harley thinks part of the cause of the confusion is that some people talk about the exposure to DU as if people in the area are starting with a zero dose, which simply isn't so. She offers a useful comparison.
"If you're in a concentration of uranium in the air from an exploded weapon, the actual dose you'll receive from breathing this is on the order of one percent of what you receive every year from natural radiation."
The question of dose causes a lot of misunderstanding. The United States Defense Nuclear Agency has reported that depleted uranium could present an exposure rate up to 200 millirems of radiation per hour on contact. This sounds like a huge dose, since they also say the maximum environmental limit is only 100 millirems per year.
"The agencies that set standards permit normal populations to be exposed to an extra 100 millirems per year over normal background. Now, if you put your hand on a big slab of depleted uranium for an hour you could get this 200 millirems. This is why the military is educating people who work with these weapons to minimize their time around them. But no one is expected to really be exposed that way, sitting next to anything that radioactive, for any great length of time. When you compare what you actually receive while sitting in a tank or holding a tank round, it's small compared to what is accepted normally," Harley says. "Besides, soldiers in a tank are only exposed to shielded depleted uranium, further reducing their exposure."
Some sources have reported that when depleted uranium hits a target, the particles released become a ceramic that can lodge in the lungs and cause damage. According to Harley, these particles that were once referred to as "high-fired" material are now called ceramic. Such tiny bits of material were first observed after atomic explosions.
"These are simply very insoluble particles," Harley says. "But when you inhale these, the lung has a very efficient mechanism for cleansing itself. First of all, when you inhale any material only a small fraction actually deposits in the lung. Most of it is exhaled, just as you see in cigarette smoke."
Most of what remains in your lungs is cleared away by the body's normal mechanisms. Some of it dissolves into the blood, washes through the kidneys and floats out in the urine. If the material is very insoluble, the little that remains in the lung dissolves very slowly.
"So the less soluble it is," Harley explains, "the smaller dose you get in other organs. And the lung eventually clears virtually all the radioactivity in it."
Some people are skeptical about the degree of confidence scientists can have in their understanding of depleted uranium's effects because little research has been done on it. Harley says scientists can be so sure because there's been a great deal of research on natural uranium.
"Depleted uranium is mostly the isotope called uranium 238," Harley says. "This is the same substance that's in natural uranium. Natural uranium has three isotopes in different ratios. Uranium 238 is by far the majority. Then you have a little uranium 235 and a little uranium 234. These are the fissionable isotopes, and U235 is what you use to make fuel for nuclear reactors and weapons. They take out this very small mass and you're left with U238, which is depleted uranium. So natural uranium is actually more radioactive than depleted uranium -- about 60 percent more. But otherwise you're actually talking about the exact same material. And this is a well-studied substance. There's much literature on how much you take in every day in diet and water and breathing air. People have measured the contents in body organs. From these data, we can really understand the biology of uranium."
When discussing depleted uranium left on the battlefield, critics have pointed out its long half-life, implying it will poison the environment for hundreds of years. But Harley says the longer the half-life, the less danger exists.
"The half life of uranium 238 is over 4 billion years," she says. "If you have 1,000 atoms of uranium it will take over 4 billion years for half of them to disappear or decay. That's the radiation, alpha particles that are emitted when the uranium atom does decay."
She says that means that depleted uranium is only slightly radioactive.
"Again, you already have this enormous amount of uranium present in all soil, all rock, and it's doing the same thing. And because it has a very long half-life, even if you get a few milligrams in your body, it exposes you to a very small amount of radioactivity because it's decaying so slowly. That's why the radiation dose is very low."
Some doctors report finding traces of depleted uranium in the urine of service members years after any possible exposure. This sounds hazardous, but Harley says this is only possible if the military members have depleted uranium fragments embedded in their bodies.
"The fragments will be dissolving very slowly," she says. "This gets into the blood stream, but uranium is cleared very quickly out of the blood stream. It will come out in the urine. In fact, you estimate what's in the body from measured urine samples. Doing this type of measurement is very important, and I'm a strong proponent of doing lots of measurements on veterans."
Some veterans are convinced that the fragments could be inhaled particles lodged in their lungs. Harley disagrees.
"It's hard to imagine that anybody could have inhaled enough material so that it could still be there eight or nine years later, enough so that you could see the amount being dissolved and then getting into urine."
Still, none of this makes it easy to dismiss the fact that concerned people around the world have called depleted uranium a dangerous radioactive waste material that might contaminate the water and food wherever it's used. Harley attributes these alarmist cries to a basic fear of radioactivity in general. And despite the many symptoms some people want to blame on exposure to depleted uranium, cancer is the only illness known to be caused by radiation. And even then, Harley says, the ore - uranium - is not the culprit.
"In uranium mines, the thing that actually causes cancer is inhaled radon gas. Cancer is not associated with any of the properties of the ore. What's in the environment normally does go into the food and water. There's a little bit in the air from resuspension. There's so much there naturally that what's put down in battle can't add anything significant in the way of dose or risk."
Harley says she's heard people project that the use of depleted uranium will cause tens of thousands of new cancers in Gulf War veterans and Iraqi citizens, but she says such projections frighten veterans unnecessarily because there is no scientific support for such claims.
"There is no way you can get enough uranium into the body to cause even one cancer," she says. "You can't inhale it, you can't ingest it. You would choke to death before you could inhale that much material."
Though the causes of some Gulf War illnesses are still unknown, there is no scientific evidence to date that depleted uranium is one of them. Much of that scientific evidence can be found in the GulfLINK depleted uranium section.