Answer to Question #1053 Submitted to "Ask the Experts"

Q

Last summer I met someone who was in the military during the time of the Persian Gulf. He told me that he had 3 rem of plutonium in his lungs. He seemed to think that it was inevitable that he would get cancer. I have tried to find information on the topic and the data seems to be conflicting. Is cancer an inevitable outcome? He said he received the exposure during an accident on a navy ship, but would not go into more detail because of the classifed nature of the situation. I would appreciate receiving information which I will forward to him.

A

The answer to your question, "Is cancer an inevitable outcome [of radiation exposure to the lung]?", is NO IT IS NOT. In fact, if the dose to your acquaintance's lung is actually 3 rem there is little likelihood of cancer being caused by this exposure.

Before giving the details of this answer I would like to address a couple of aspects of the background material leading to the question that warrant some clarification or comment. Although I worked as a health physicist for 26 years for the Department of the Navy, I do not know of any possible way someone could be exposed to plutonium from an accident on a navy ship. The primary sources of measurable amounts of radioactivity contamination following an accident on a navy ship are accidents involving the power plant on a nuclear-powered ship or a weapon with a nuclear warhead. Nuclear navy power plants cannot result in contamination with plutonium. Nuclear warheads cannot result in contamination with plutonium unless the explosives (not the nuclear warhead) detonate, causing severe damage to the ship.

Recently there has been media coverage about the concerns for health effects to our armed forces in the Persian Gulf war from the use of armor-piercing shells made with depleted uranium and the possibility these had small amounts of plutonium in addition to the depleted uranium. I am not aware of shells on navy ships made with depleted uranium, but I don't know all the types of ammunition the various navy ships carry. Even if they did have depleted uranium shells they would have to vaporize the shell on the ship to make it possible to breathe in the radioactive materials, which would be an extremely damaging accident to the ship.

However, assuming the statement that your acquaintance received 3 rem from exposure to some radioactive material is true, it does not matter what type of radioactive material caused the exposure. A "rem" is a unit of the measure of the radiation dose to an organ, like the lung, and the consequence of this exposure is the same regardless of the source of the radiation. Dose to internal organs due to radioactive material depositing in the organ is spread out over a long period of time. The length of time internally deposited radioactive material continues to deliver its dose depends on how long it takes the radioactive material to decay (measured by the "half-life" of the radioactive material) and how long it takes for the body to eliminate the material. The biological elimination of the material depends on the chemical and physical nature of the radioactive material. The dose from internal radioactive materials is calculated for a 50-year period. Therefore, if the radioactive material has a long half-life, like plutonium, and is of a chemical and physical nature to not be easily removed by the body, such as most compounds of plutonium, the dose will be evenly spread out over a 50-year period. This means the dose to the lung in any one year is about six one-hundredths (0.06) of a rem.

For perspective, this annual dose of 0.06 rem is less than the annual dose of 0.1 rem allowed by federal regulations to a member of the public from man-made sources of radiation (other than medical uses, which has no limit). This is also less than the dose an individual gets from natural cosmic radiation each year by living in Denver, the mile-high city, as compared to living at sea level. The total dose of 3 rem to the lung is also small. For perspective, a radiation worker is allowed to get an exposure of approximately 42 rem from one year of work, provided the dose to the lung is the only exposure the worker receives. This is also only slightly larger than the average lung dose received by United States residents from radon exposure each year, with many residents receiving much more than 3 rem each year. Increases in lung cancer have not been observed in scientific studies of groups of people exposed to radiation at doses less than 10 rem.

The Health Physics Society does not recommend that the risk of cancer at doses less than about 10 rem should be calculated since the dose is too low to result in observable cancers in these scientific studies. However, using the US Environmental Protection Agency's method of calculating the risk of 3 rem to the lung results in a hypothetical estimate that in a group of 10,000 adults receiving 3 rem to the lung, two may develop a cancer from this exposure. This may to be compared to approximately 3,000 of each 10,000 people who are expected to get a cancer in their life.

You may find additional information of interest by reading the Health Physics Society's position statement titled "What About Deadly Plutonium?" or the position statement titled "Radiation Risk in Perspective".

Keith Dinger, CHP