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A medical look at plutonium.

Plutonium is toxic as a result of its radioactivity.

Plutonium is a heavy metal like cadmium and lead. Both are toxic. However, the toxicity of plutonium is worse than could be expected from its 'heavy metal character'. In fact, its toxicity comes from its radioactivity, which is even more malicious than that of most other radioactive materials. Uranium is mildly radioactive and can be held safely in the hand, though it is not wise to make a bed of it. Plutonium is much more radioactive (see the analogy with the gunners page 9) but surprisingly it can also be held safely, as long as one avoids direct contact with the skin and prevents it from entering the body. This is explained by the special quality of its radioactivity. The "radiation packets" that are produced by plutonium, the so-called 'alpha particles', emerge with great velocity from the plutonium nuclei, but they do not penetrate deeply: the impact craters are less than one tenth of a millimetre deep in the tissues (see figure). Here many cells will be killed or damaged. Some of these damaged cells become malignant and will start a cancer.

Plutonium dust originates from inadvertent criticality.

Plutonium dust can be formed in, for example, a so-called criticality accident. We have seen before that plutonium can be held safely in gloved hands. However, if a smuggler should be too successful he risks a disaster. If he should add a new container of plutonium on top of his pile, the total mass of plutonium may become supercritical. Right in front of him the smuggler may witness what is also happening deep in the core of a nuclear reactor: the very chain reaction of nuclear fissions itself. In the exploding nuclear bomb, a similar process takes place, but very fast, in a flash. In a supercritical pile this happens in ominous silence.

Most likely the unfortunate smuggler only sees a sudden blue light and he feels a hot glow passing. Near the centre of his stack some smoke may emerge. The chain reaction stops spontaneously, because the supercritical mass has expanded by the heat and fallen apart. Perhaps some packages are still burning a little.

The smuggler however is beyond medical help. Within a few seconds he has received a dose of radiation that equals thousands of X-ray pictures right through his body. That same night he will fall ill. Within days he will die of radiation sickness.

Meanwhile the immediate environment is also in danger. The smoke contains a fine powder of plutonium oxide. The powder becomes lodged by inhalation in the lungs and many years later lung cancer may develop.

Criticality is a treacherous property of plutonium and may come to light when an amount of about 10 kilograms is available: this is the size of a large grapefruit if it is pure and closely packed. However, a pile of bags with plutonium would probably need to exceed 100 kilograms before it becomes supercritical. The average distance between the plutonium atoms is much larger in this case, making the chain reaction less probable. Adding water sharply increases the probability of a chain reaction. The fire brigade had better know that.

Plutonium dust may cause lung and bone cancer.

If somebody inhales plutonium dust, he won't notice anything special. Only 10 to 50 years later is it possible that lung and bone cancer may develop. Once in the lungs, the plutonium dust stays there for many years: sparks that fail to extinguish. Ten per cent of the original dose in the lungs can still be found there after fifteen years (as experiments with beagle dogs have shown). Very slowly the particles move to the lymph nodes of the lungs. When it appears in the blood plutonium "seeks" the bones and the liver. Even when the concentration of the plutonium dust in the air is very low, accumulation of this plutonium in the lung may become a serious burden. The animal experiments have allowed scientists to calculate what may happen in human lungs after inhalation of plutonium dust. They found that as little as a 27 millionth of one gram of plutonium dust (27 micrograms of ²³⁹Pu oxide) is enough to cause a lung cancer. That is why in the handbooks the maximum permissible concentration of plutonium is among the lowest of all radioactive substances.

NB:

Plutonium in food or drinking water is not an important issue, because it is hardly taken up by the gut.

Plutonium is not dangerous outside the body.

What is the evidence regarding humans up till now?

Despite some big inadvertent releases of plutonium into the environment the causation of any disease by plutonium in man still awaits formal proof.

-For example, during fires in the US nuclear weapons complex Rocky Flats near Denver in 1957 and 1969 clouds of smoke containing plutonium dust spread over the town. However, the expected "epidemic" of lung cancer and congenital defects did not occur. Probably the plutonium dust did not reach the population because it came down quickly and became firmly adhered to the soil. Besides, extra cases of cancer or birth-defects in babies are difficult to distinguish from what people acquire "naturally". More importantly, the number of new cases of disease varies spontaneously from year to year. Thus a sudden increase in the number of cases of cancer in a given region is hard to accept as proof of the "guilt" of plutonium: it could also have been a coincidence.

-Atmospheric testing between 1945 and 1963 brought 4.2 tons of plutonium dust directly into the environment. Most of this went up high into the stratosphere. There it was diluted and gradually came down. In theory 7,900 cases of cancer may have been caused by this plutonium. That is the conclusion of the International Physicians for the Prevention of Nuclear War in their book "Radioactive Heaven and Earth" (1991). Again, no direct evidence is available to substantiate this statement. On the other hand, it is a fact that plutonium-dust can cause cancer (plutonium is "carcinogenic").

Radioactive contamination may cause hereditary abnormalities and congenital defects.

The hereditary material (DNA) in spermatozoa or in egg-cells can be damaged by radiation. The resulting DNA-defects may be transmitted to the offspring. Fortunately the body of the mother selects every foetus for viability. If that is insufficient a miscarriage follows. But sometimes the selection is not severe enough. The pregnancy may continue despite some defect or even a lethal disease in the child.

Just as in the case of cancer, it is not possible to differentiate between a congenital defect caused either by contamination, "by nature" or by other influences. However, every mother and father struck by such a misfortune will wonder as to its cause.

Radioactive contamination in the past is an easy scapegoat, but it is impossible to prove a relationship with certainty. Perhaps more importantly, it is impossible to disprove it.

Plutonium on the beach.

A report by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR; 1988, table 63, page 228) shows that plutonium was present in fish and shell-fish near Sellafield (England, Cumbria) in 1983.

Since then the larger leaks of plutonium in Sellafield have come to an end, but many inhabitants feel insecure. The time elapsing between contamination and cancer is 10 - 50 years. The fact that plutonium has never proved to be a cause of cancer in human beings does not convince the parents of a child with leukaemia.

An ominous increase of the occurrence of leukaemia around Sellafield and Cap la Hague has been found, but the sad and angry population lost a law suit against the British Nuclear Fuel Limited (BNFL, at Sellafield) to prove causality.

Medical experiments on people

During and just after the Second World War the further development of atomic bombs was deemed necessary. In that context the medical effects of plutonium on human health were investigated. Doctors injected patients with plutonium solutions without telling them. Also prisoners, mentally retarded people and even pregnant women were used. Obviously these treatments were not supposed to be of any benefit to the "patients".

Medical ethics.

In former times medical experiments were said to be carried out "on" persons, now "with" them. In every hospital a committee on medical ethics scrutinises unusual treatments or those which are obviously not in the interest of a particular group of patients. The committee checks whether the information given is true and understandable for everybody. Attached to this information is a clause that if the patient would rather not co-operate, this refusal will not harm his or her position with the doctor. In this way clinical research can proceed with the help of patients who can decide in true freedom.

This is called: "informed consent".

Risk-feel: facts or fear?

People's perception on health risks is variable. Much depends on one’s own lifestyle.

If a patient with cancer has received a small amount of radioactive contamination in the past, it is not probable that this contamination was the real cause of his disease. Nevertheless many patients fight fiercely for "satisfaction", forgetting the cigarettes they smoked.

In general people tend to accept health risks, provided there is a profit and the damage is under control. In other words, people readily take risks if:

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  they take the initiative of their own free will
  
• 
  they have a clear picture of what exactly can go wrong
  
• 
  they have the power (freedom) to evade any side-effects
  
• 
  they can protect their children
  
• 
  the chance of a great set-back is low
  
• 
  they assume an eventual set-back will not happen in their own backyard
  
• 
  the chance of a small set-back outweighs the profit
  
• 
  they like and trust the people handling the risky technique
  

In the special case of nuclear power the picture looks quite different. Electricity is worth a risk, but a person's own free will can hardly be effective because of the lack of information due to the secrecy around the nuclear technology, all over the world. There are valid reasons for concern about health risks. The public relations practice of the nuclear providers lags behind the modern medical ethical rules of informing patients.

Facts and fear make plutonium an expensive heritage.

Nuclear technologies are associated with the risk of contamination of the environment. Houses in contaminated areas go down in their value, because of the "risk-feel" of the potential buyers. Physicians cannot guarantee which amount of contamination is safe since there is no level below which radioactivity has no effect. Calculation may reveal that the risk is very low, but not being zero reassurance may fail. Fear is part of reality. The financial consequences can go sky-high. That's why insurance companies exclude all claims for damage through radioactive contamination.

The money-eating robotics to remove old reactors, to handle contaminated soil and to put nuclear waste into final repositories is thriving because of severe laws and because the personnel no longer want to volunteer for risks.

Plutonium is an eternal poison.

Plutonium becomes gradually stable by radioactive decay. That sounds reassuring. If we just wait long enough, all radioactive material will vanish.

However, it takes 24,400 years before half of a given amount of the most common sort of plutonium has decayed in this way. The other half needs another 24,400 years to decay to 50 % and the quarter that remains again, etcetera. (see page 9-10 on "half-life").

Requirements for a plutonium repository cannot be formulated in practical terms. To illustrate this consider the ancient graves. Had the Egyptian Pharaoh Cheops been given 1000 grams of a civil plutonium-mix in his grave after his death in 2600 BC, about 684 grams of radioactive plutonium would still be left in the great pyramid.