The Human Plutonium Injection Experiments

 

O

ver the past fifty years, thousands of workers in the United

States have handled plutonium.  Of those workers, only about

fifty, all from the nuclear-weapons complex, have been exposed

to plutonium at levels above the maximum permissible dose.  Because

so few people have high-dose exposures, we have little direct informa-

tion about the risk of plutonium in man.  This leads to the ironic situa-

tion that the better we protect our workers, the less we know about

their risk.  What then do we use to base our decisions about the risk of

plutonium and the precautions we need to take to safeguard workers

against that risk?

Much of our understanding of

the health risk posed by plutoni-

um is based on another element,

radium.  Like plutonium, radium

is an alpha-emitting radioisotope,

but it is created naturally as a

decay product, or daughter, of

uranium.  As described below,

thousands of people were exposed

to radium before 1932, and the ef-

fects of the many high-dose expo-

sures became apparent after just a

few years.  That grievous situation

none-the-less provided scientists

with a group of people who were ex-

posed internally to an alpha-emitting

radioisotope, and who could be ob-

served, evaluated, and studied.  In 1944, the risk associated with the

new manmade element plutonium was therefore estimated by scal-

ing the risks associated with radium.  That initial estimate was soon

modified to take into account new animal data on the comparative

toxicity and distribution in the bone of radium versus plutonium.

But even today, much of our understanding of the risk of plutonium

to humans and much of the public's perceptions about the dangers of radioactive

materials are grounded in the story of radium.

That story began in 1898 when Marie and Pierre Curie discovered radium.  The

announcement at the French Academy of Science of a new radioactive material

followed just two years after Henri Becquerel’s discovery of radioactivity in urani-

um.  Radium was only the third radioactive element to be identified (polonium

was the second—also discovered in 1898 by the Curies).  Radium was very

scarce; after four years of hard labor, the Curies were able to separate only 100

milligrams of the pure element (roughly equivalent in volume to the the head of a

match) from several  tons of uranium ore.  It was therefore very expensive, and as

late as 1921, one gram of radium cost $100,000.  However, the extraordinary at-

tributes of radium made it worth the cost.  The half-life of radium is 1600 years,

as opposed to only 138 days for polonium and 4.5 billion years for uranium (see

“Ionizing Radiation—It’s Everywhere!” pages 24-25, for a discussion of radioac-

tive half-life).  Radium was thus a stable source of radiation for hundreds of years

The Human Plutonium Injection Experiments

224

 

Los Alamos Science Number 23  1995

Radium–the Benchmark         for Alpha Emitters

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with an intensity three-thousand times greater than an equal amount of uranium.

In other words, radium combined a long life with radioactive intensity far better

than the other known radioactive ma-

terials, and it was eagerly put to a

great number of uses.

Cancer treatment was among the ear-

liest and most beneficial applications

of radium.  The idea derived from an

incident that occurred in 1901 in

which Becquerel, eager to carry out

some impromptu demonstrations, car-

ried a tube of radium that was loaned

to him by the Curies in his shirt

pocket for six hours.  Ten days later,

he developed a small erythema, or

reddening of the skin, identical to

that produced by x rays.  It was clear

that emanations from the radium

sample could affect skin tissue, and

that perhaps, like x rays, such emana-

tions could be used as a treatment for

cancer.

That idea proved to be successful,

and in 1906, the Biological Laborato-

ry of Paris for the practice of “radium

therapy" was established.  Applica-

tors containing radium salts were ap-

plied directly to the surface of benign

and malignant tumors to shrink or

eliminate them.  Such use of radium

dramatically improved the quality of

many lives (see Figure 1) and helped

found the modern medical field of ra-

diotherapy.  However, the radiation

that penetrated the applicators were mainly gamma rays from the radioactive

daughters of radium decay.  Once other gamma-ray-emitting radioisotopes, such as

cesium-137, became available from nuclear reactors during the 1960s, the use of ra-

dium as a radiation source for cancer treatment gradually declined and eventually

ended.

During its heyday, however, radium’s use as a cure for cancer was widely publi-

cized in the press.  The element assumed an aura that was both mysterious and

fascinating, and it was celebrated in Europe and America.  Audiences drew

around storytellers describing the danger of radium’s emanations, while at the

same time, it was touted as a miracle cure for many diseases.  The young in-

dulged themselves with radium-laced candies and sodas.  Women sought youthful

beauty in radium-containing facial creams, while the fatigued restored their vigor

The Human Plutonium Injection Experiments

Number 23  1995  Los Alamos Science  

225

for Alpha Emitters

 

Marie Curie (1867-1934), 

photo taken circa 1920.  

Inset:  Pierre Curie (1859-1906).

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