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