Radioactivity—How Does It Threaten You?
By Awake! correspondent in Britain
“RADIOACTIVE!” What comes to your mind when you hear that word? For most people, radiation is “inexplicable, unseeable, untouchable and almost mystically evil,” asserts the British House of Commons environment committee. Do you share this view?
Only a century ago, radioactivity was an unknown entity. Today, radioactive materials are used so extensively that you can often spot the characteristic hazard symbol in hospitals, on trucks transporting radioactive materials, in factories, as well as at nuclear installations. They play a significant role in modern life.
On the other hand, in the closing days of World War II, atom-bomb explosions at Hiroshima and Nagasaki unleashed massive doses of nuclear radiation and wrought unprecedented havoc and destruction. More recently, the power station accidents at Three Mile Island (U.S.A.), Chernobyl (Ukraine), and near St. Petersburg (Russia) have added to people’s fear of radioactivity.
What, then, is radioactivity? How can it threaten you?
A Powerful Phenomenon
Everything material is made up of atoms, and most atoms are stable. The exceptions, having unstable nuclei, are termed “radioactive.” Best known among them is uranium. To achieve stability, the unstable nucleus changes and, in the process, emits radiation in the form of small particles and rays. In this way the uranium is transformed into a succession of other elements and finally becomes the stable element lead.
All radiation penetrates but to different degrees. The heaviest (alpha) particles typically travel less than two inches [5 cm] through the air. Your clothes or the top layer of your skin stops them. The tiny electrons that form beta radiation pass a few yards [meters] through the air, but a thin sheet of aluminum or glass bars their progress. Far more penetrating is a third variety, gamma rays. Heavy barriers of lead or concrete can shield us from this kind of radiation. Unprotected, we are under threat. How?
How Radiation Causes Damage
When radiation of the above types penetrates the human body, it causes changes in some of the atoms in the cells along its path. This can cause chemical changes that may damage or even kill the cells. The total effect on the body depends on the extent of the damage and the number of cells killed. If the damage occurs in the DNA molecules in the chromosomes, the result may be especially serious because they govern the normal development and function of the cells. Scientists believe that this damage is linked to cancer.
Large amounts of radiation delivered in a short span of time damage both bone tissue and blood cells, causing radiation sickness and death. In September 1987 the Brazilian town of Goiânia witnessed a tragedy that Dr. Gerald Hansen of the World Health Organization reportedly described as “the worst [nuclear] accident in the Western hemisphere, second only to Chernobyl.” A scrap-metal dealer handled highly radioactive cesium powder from a discarded radiotherapy machine. He and others in the immediate neighborhood absorbed a massive dose of radiation. Fear spread as the bodies of the first victims to die were placed in lead coffins and buried in concrete-lined graves. According to The Times of London, survivors who absorbed heavy doses of radiation faced “almost certain cancer or sterility.”
Smaller radiation doses spread over a period of time also lead to a slightly enhanced risk of contracting cancer. The human body can sometimes successfully repair cells struck by radiation. When the repair is faulty, however, cancer may develop. Paradoxically, radioactivity is used in radiotherapy to target and destroy cancerous cells.
How We Get It
In the aftermath of the 1986 Chernobyl disaster, several governments imposed bans on certain foodstuffs judged to be dangerously contaminated. In Sweden, for example, the consumption of reindeer meat with a high level of radioactive cesium was prohibited. Likewise, bans were reimposed on the marketing of lambs from many farms in Wales and Scotland when radiation above the prescribed safety limit was detected in flocks reared in 1987.
While the public understandably express anxiety over the threats from contaminated foodstuffs and radioactive waste, they rarely, if ever, worry about radioactive drugs and X rays. Yet, these provide approximately 12 percent of our total annual dose. By far the greatest amount of our radiation comes from natural sources. Cosmic rays from space deliver 14 percent.a As we eat and drink, we ingest an additional 17 percent. Even the earth’s naturally radioactive rocks and soil contribute a sizable portion, namely, 19 percent. So from where does the remainder come?
‘On the edge of Dartmoor in southwestern England lies the village of Chagford. One of its buildings, used as a health center, houses what has been called the world’s most radioactive washroom. If you visited this place four times a day for 15 minutes at a time, you would be exposed to more than the recommended national annual level of a radioactive gas called radon, probably the biggest single cause of cancer in Britain after smoking.’—New Scientist, February 5, 1987.
While that report may be sensational, on the average, about a third to a half of our annual radiation dose comes from radon and its associated radioactive gas, thoron. As a gas, radon is the odd man out in the radioactive decay series that begins with uranium. Bubbling up through fissures in the bedrock, it seeps through the foundation and into the house and contaminates the air with radioactivity.
Studies by Britain’s National Radiological Protection Board discovered areas where the air is so contaminated with radon that it “would not be tolerated inside a nuclear power station,” reports New Scientist magazine. Indeed, the board estimates that 20,000 homes in Britain have concentrations of radioactivity exceeding ten times the usual annual radiation dose. Because many modern homes are tightly draft proofed, they trap the radioactive gases inside and increase the incidence of lung cancer.
Though the risks may be small, they are not insignificant. According to present estimates, about 2,500 people a year in Britain contract lung cancer from radon’s radioactivity. In the United States, where a ten-state survey revealed that a fifth of all homes have levels of radon considered unsafe, it is estimated that from 2,000 to 20,000 deaths a year result from lung cancer brought on by the gas. From Sweden researchers report that because of radon gas trapped in gravel, levels of radioactivity in some houses there are calculated to be four times those in Britain.
How Real the Risks?
“As far as anybody knows,” comments The Economist, “any one single [gamma] ray can cause cancer and the more rays that go through your body, the more chance there is of one doing damage.” But it adds reassuringly: “The probability of one doing so is tiny.”
The risk that a person will develop a fatal cancer by exposure to a dose of one millisievert (over and above the doses from natural background) is, according to ICRP (International Commission on Radiological Protection), one in 80,000.b Thus, ICRP gives the advice that “no practice should be adopted unless its introduction produces a net positive benefit.” It recommends that “all exposures shall be kept as low as is reasonably achievable, economic and social factors being taken into account.”
The United Kingdom Atomic Energy Authority believes that the risk of radiation-induced cancers from such a dose may be even lower. On the other hand, environmental pressure groups, backed by a number of researchers, claim that recommended safety levels should be reduced. One suggests that the ICRP’s guideline be changed to read that all exposures should be kept “as low as technically achievable.”
Meanwhile, is there anything you can do to protect yourself from the radiation threat? Yes, there certainly is.
Precautions You Can Take
Just as you can take precautions to protect yourself from overexposure to the sun and thus avoid skin cancer, you can take precautions to protect yourself from the hazards of radioactivity. So search out and follow the warnings.
If you live in an area where there are radon-producing rocks, you may be able to install ventilation for the foundation of your house that will help avert a dangerous buildup of the gas in the house. On being prescribed medical examinations that use radioactive materials or X rays, ask your doctor how necessary they are. Perhaps he can suggest a less hazardous alternative. And when you see the radiation-hazard symbol, take adequate precautions to follow the safety procedures outlined for the area.
Invisible and untouchable, radioactivity surely is. But if kept in its place, radioactivity’s menace diminishes. Under perfect conditions, it will threaten no more.
a Cosmic radiation differs from the nuclear radiation emitted by radioactive materials.
b The sievert is a measure of the amount of energy that radiation imparts to body tissues. One millisievert (mSv) is a thousandth of a sievert. The average annual dose in Britain is about 2 mSv, and a chest X ray gives about 0.1 mSv.
[Diagram/Picture on page 13]
(For fully formatted text, see publication.)
A—Food and drink
B—Radon and thoron
C—Rocks and soil
Picture D: Holiday Films
[Picture Credit Lines on page 11]
Photos: Top left and bottom right, U.S. National Archives photo; bottom left, USAF photo; bottom second from left, Holiday Films