Answer to Question #746 Submitted to "Ask the Experts"

Q

How are bullets made by depleted uranium, and what reactions do they cause when they enter into contact with the ground and with humans?

A

Because of its very high density—nearly twice that of lead—and certain other properties, depleted uranium is used in certain kinds of munitions because of its ability to penetrate heavily armored vehicles such as tanks and armored personnel carriers. Depleted uranium (DU) is not used in small cartridges or bullets for rifles or machines guns but alloyed DU is used in the 25, 105, and 120 millimeter (mm) kinetic energy cartridges used primarily as antitank munitions. DU is also a component in some tank armor and sometimes used as a catalyst for land mine systems.

Since depleted uranium is weakly radioactive, the public has been concerned about the possiblility of adverse health effects from DU. DU is a heavy metal, and like all heavy metals such as mercury and lead, is toxic. However, except in certain very unusual situations, it is the chemical toxicity and not the radioactivity that is of concern. And, from a chemical toxicity standpoint, uranium is on the same order of toxicity as lead. Largely from work with animals along with a few instances in which humans inhaled very large amounts of uranium, the chemical toxicity of uranium is known to produce minor effects on the kidney, which in humans who have suffered large acute exposures have been transitory and wholly reversible. Because depleted and natural uranium are only weakly radioactive, radiological effects from ingested or inhaled uranium have not been detected in humans.

Human experience with uranium has spanned more than 200 years. In the early part of the twentieth century, uranium was used therapeutically as a treatment for diabetes, and persons so treated were administered relatively large amounts of uranium by mouth. Tens of thousands of persons have worked in the uranium industry over the past several decades, and have been followed up and studied extensively as have populations in Canada and elsewhere who have high levels of uranium in their drinking water. Results of these studies have not revealed any ill health in these populations that is attributable to the intake of uranium. This is not surprising, as the risk from the radiation dose from uranium is far overshadowed by its potential chemical toxicity, and intakes of uranium of sufficient magnitude to produce chemotoxic effects are unlikely in and of themselves. Any such effects from ingestion or inhalation of uranium would likely manifest themselves first in the form of minor effects associated with the kidneys. That military personnel and others who may have had contact with depleted uranium from munitions are suffering from various illnesses is not in dispute. That their illnesses are attributable to their exposure to uranium is very, very unlikely. Health physicists are deeply concerned with the public health and welfare, and as experts in radiation and its effects on people and the environment, are quite aware that something other than exposure to uranium is the cause of the illnesses suffered by those who have had contact with depleted uranium from munitions. A truly enormous body of scientific data shows that it is virtually impossible for uranium to be the cause of their illnesses. Despite this body of scientific data to the contrary, misguided or unknowing people continue to allege that the depleted uranium, and specifically the radioactivity associated with the depleted uranium is the cause of these illness. This is indeed unfortunate, for health physicists and other scientists and physicians already know that depleted uranium is not the cause of these illnesses and thus any investigations into the cause of these illnesses should focus on other possible causes.

If we are to offer any measure of relief or solace to these suffering people, and to gain some important additional knowledge of the cause of their illness, we should not waste our valuable and limited energies, resources, and time attempting to point the finger at depleted uranium as the culprit, when it is already known that uranium is almost certainly not the cause of the problem. With respect to reactions with the soil, in time depleted uranium will likely leach into the soil and become mixed with it. It will for all practical purposes be chemically indistinguishable from the natural uranium that is already present in the soil all over the earth. One could create all kinds of scenarios, but probably the best way to think about DU in the soil is to compare it with lead. Because lead and uranium are so similar from a toxicological standpoint, the concerns are about the same.

Ronald L. Kathren, CHP
Professor Emeritus Washington State University