Health Effects of Plutonium

To counter mainstream media’s psyops campaign that plutonium is safe, here is a 1997 article by a nuclear fission expert on the health effects of the deadly substance. ~Ed.

By Dr Arjun Makhijani
Institute for Energy and Environmental Research
December 1997

Plutonium-239 is a very hazardous carcinogen which can also be used to make nuclear weapons. This combination of properties makes it one of the most dangerous substances. Plutonium-239, while present in only trace quantities in nature, has been made in large quantities in both military and commercial programs in the last 50 years. Other more radioactive carcinogens do exist, like radium-226, but unlike plutonium-239 cannot be used to make nuclear weapons, or are not available in quantity. Highly enriched uranium (HEU) can also be used to make nuclear weapons, but it is roughly one thousand times less radioactive than plutonium-239. The danger is aggravated by the fact that plutonium-239 is relatively difficult to detect once it is outside of secure, well-instrumented facilities, or once it has been incorporated into the body. This is because its gamma ray emissions, which provide the easiest method of detection of radionuclides, are relatively weak.

The main carcinogenic property of plutonium-239 arises from the energetic alpha radiation it emits. Alpha particles, being heavy, transfer their energy to other atoms and molecules within fewer collisions than the far lighter electrons which are the primary means of radiation damage for both gamma and beta radiation.1 Alpha particles travel only a short distance within living tissue, repeatedly bombarding the cells and tissue nearby. This results in far more biological damage for the same amount of energy deposited in living tissue. The relative effectiveness of various kinds of radiation in causing biological damage is known as “relative biological effectiveness” (RBE). This varies according to the type of radiation, its energy, and the organ of the body being irradiated. A simple factor, called quality factor, is used to indicate the relative danger of alpha, beta, gamma and neutron radiation for regulatory purposes. The International Commission on Radiation Protection currently recommends the use of a quality factor of 20 for alpha radiation relative to gamma radiation.2

Once in the body, plutonium-239 is preferentially deposited in soft tissues, notably the liver, on bone surfaces, in bone marrow and other non-calcified areas of the bone, as well as those areas of the bone that do not contain cartilage. Deposition in bone marrow can have an especially harmful effect on the blood formation which takes place there. By contrast, radium-226, another alpha emitter, is chemically akin to calcium and so becomes deposited in the calcified areas of bones.

When it is outside the body, plutonium-239 is less dangerous than gamma-radiation sources. Since alpha particles transfer their energy within a short distance, plutonium-239 near the body deposits essentially all of its energy in the outer dead layer of the skin, where it does not cause biological damage.

The gamma rays emitted due to plutonium-239 decay penetrate into the body, but as these are relatively few and weak, a considerable quantity of plutonium-239 would be necessary to yield substantial doses from gamma radiation. Thus, plutonium-239 can be transported with minimal shielding, with no danger of immediate serious radiological effects. The greatest health danger from plutonium-239 is from inhalation, especially when it is in the common form of insoluble plutonium-239 oxide. Another danger is absorption of plutonium into the blood stream through cuts and abrasions. The risk from absorption into the body via ingestion is generally much lower than that from inhalation, because plutonium is not easily absorbed by the intestinal walls, and so most of it will be excreted.

The kind of damage that plutonium-239 inflicts and the likelihood with which it produces that damage depend on the mode of incorporation of plutonium into the body, the chemical form of the plutonium and the particle size. The usual modes of incorporation for members of the public are inhalation or ingestion. Plutonium may be ingested by accidental ingestion of plutonium-containing soil, or through eating and drinking contaminated food and water. Incorporation via cuts is a hazard mainly for workers and (in former times) for personnel participating in the atmospheric nuclear testing program.

In general, plutonium in the form of large particles produces a smaller amount of biological damage, and therefore poses a smaller risk of disease, than the same amount of plutonium divided up into smaller particles. When large particles are inhaled, they tend to be trapped in the nasal hair; this prevents their passage into the lungs. Smaller particles get into the bronchial tubes and into the lungs, where they can become lodged, irradiating the surrounding tissue.

Other plutonium isotopes that emit alpha radiation, like plutonium-238, have similar health effects as plutonium-239, when considered per unit of radioactivity. But the radioactivity per unit weight varies according to the isotope. For instance, plutonium-238 is about 270 times more radioactive than plutonium-239 per unit of weight.

Experimental data

The health effects of plutonium have been studied primarily by experiments done on laboratory animals. Some analyses have also been done on workers and non-worker populations exposed to plutonium contamination. Measurements of burdens of plutonium using lung counters or whole-body counters, together with follow-up of exposed individuals, have provided information which is complementary to experimental data and analysis. Experiments injecting human beings with plutonium were also done in the United States. Between 1945 and 1947, 18 people were injected with plutonium in experiments used to get data on plutonium metabolism. They were done without informed consent and have been the object of considerable criticism since information about them became widely known in 1993.

Experiments on beagles have shown that a very small amount of plutonium in insoluble form will produce lung cancer with near-one-hundred-percent probability. When this data is extrapolated to humans, the figure for lethal lung burden of plutonium comes out to about 27 micrograms. Such an extrapolation from animals, of course, has some uncertainties. However, it is safe to assume that several tens of micrograms of plutonium-239 in the lung would greatly increase the risk of lung cancer. Larger quantities of plutonium will produce health problems in the short-term as well.

The precise quantitative effects of considerably lower quantities of plutonium are as yet not well known. This is due to several factors such as: the difficulty of measuring plutonium in the body; uncertainties regarding excretion rates and functions due to the large variation in such rates from one human being to the next (so that the same body burden of plutonium would produce considerably different doses); complicating factors such as smoking; uncertainties in the data (as, for instance, about the time of ingestion or inhalation); differing and largely unknown exposure to other sources of carcinogens (both radioactive and non-radioactive) over the long periods over which studies are conducted; failure to study and follow-up on the health of workers who worked with plutonium in the nuclear weapons industry to the extent possible.

One of the few attempts to analyze the effects of microgram quantities of plutonium on exposed human subjects was a long-term study of 26 “white male subjects” from the Manhattan Project exposed to plutonium at Los Alamos in 1944 and 1945, where the first nuclear weapons were made. These subjects have been followed for a long period of time, with the health status of the subjects periodically published. The most recent results were published in a study in 1991.3

The amounts of plutonium deposited in the bodies of the subjects were estimated to range from “a low of 110 Bq (3 nCi) …up to 6960 Bq (188 nCi),”4 corresponding to a weight range of 0.043 micrograms to 3 micrograms. However, weaknesses in the study resulted in considerable uncertainties about the amount and solubility of plutonium actually incorporated at the time of exposure.5

Of the seven deaths by 1990, one was due to a bone cance (bone sarcoma).6 Bone cancer is rare in humans. The chances of it normally being observed in a group of 26 men over a 40-year timeframe is on the order one in 100. Thus, its existence in a plutonium-exposed man (who received a plutonium dose below that of current radiation protection guidelines) is significant. 7 There are data for plutonium exposure in other countries, notably in Russia. These are still in the process of being evaluated. Collaborative US-Russian studies are now beginning under the Joint Coordinating Committee on Radiation Effects Research (JCCRER) to assess the health effects of the Mayak plant to both workers and neighbors of the facility.

Endnotes

1. Gamma rays consist of high energy photons, which are “packets” or quanta of electromagnetic energy.

2. The energy deposited in a medium (per unit of mass) is measured in units of grays or rads (1 gray = 100 rads), while the biological damage is measured in sieverts or rems (1 sievert = 100 rems).

3. G.L.Voelz and J.N.P. Lawrence, “A 42-year medical follow-up of Manhattan project plutonium workers.” Health Physics, Vol. 37, 1991, pp. 445-485.

4. Ibid., p. 186.

5. These aspects of the study are discussed in some detail in Gofman 1981, pp. 510-520 (based on the status of the Manhattan Project workers study as published in Voelz 1979). See J.W. Gofman, Radiation and Human Health, (San Francisco: Sierra Club Books, 1991), p. 516.

6. Three of these deaths were due to lung cancer. It is difficult to assess the significance of this large percentage, since all three were smokers.

7. Voelz, p. 189.

Arjun Makhijani, President of IEER, holds a Ph.D. in engineering (specialization: nuclear fusion) from the University of California at Berkeley. He has produced many studies and articles on nuclear fuel cycle related issues, including weapons production, testing, and nuclear waste, over the past twenty years. He is the principal author of the first study ever done (completed in 1971) on energy conservation potential in the U.S. economy. Most recently, Dr. Makhijani has authored Carbon-Free and Nuclear-Free: A Roadmap for U.S. Energy Policy (RDR Books and IEER Press, 2007), the first analysis of a transition to a U.S. economy based completely on renewable energy, without any use of fossil fuels or nuclear power. He is the principal editor of Nuclear Wastelands and the principal author of Mending the Ozone Hole, both published by MIT Press.

Also see: Radioactive iodine releases from Japan’s Fukushima Daiichi reactors may exceed those of Three Mile Island by over 100,000 times, March 25, 2011.