URANIUM: A Discussion Guide: QUESTIONS AND ANSWERS
by Dr. Gordon Edwards et al.
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prepared for and published by The National Film Board of Canadainvited address by Dr. Gordon Edwards at the World Uranium Hearings
Salzburg, Austria
September 14, 1992
E.1. What are the health hazards of uranium mining?
Uranium mining is hazardous. In addition to the usual risks of mining, uranium miners worldwide have experienced a much higher incidence of lung cancer and other lung diseases. Several studies have also indicated an increased incidence of skin cancer, stomach cancer and kidney disease among uranium miners.
E.2. How long have we known that lung cancer is caused by uranium mining?
For four centuries, beginning in 1546, it was reported that most underground miners in Schneeburg, Germany, died from mysterious lung ailments. In 1879 it was shown that up to three quarters of them were dying of lung cancer, and many of other lung diseases.
By 1930, the same grim statistics were found among miners in Joachimsthal, Czechoslovakia, on the other side of the same mountain range. More than half of them were dying of lung cancer. Among the non-mining populations on both the German and Czech side of the mountains, lung cancer was all but unknown.
The ores in question were particularly rich in uranium. Men who mined other types of ores were not found to suffer the same epidemic of lung cancer as these miners did.
E.3. How did we learn that radioactivity causes lung cancer?
In 1897 it was learned that uranium ores are radioactive. By 1900 it was found that severe skin damage can be caused by prolonged contact with some of the radioactive decay products of uranium. By 1920 it was well established that chronic exposure to atomic radiation, even without any visible damage to skin or other bodily tissues, can cause cancers and leukemias, years later, in both humans and animals.
By the 1930s, scientists were convinced that the centuries-old lung cancer epidemic among German and Czechoslovakian miners was caused by the men inhaling airborne radioactive materials in the underground mines. Decades later, Japanese atomic bomb survivors were found to have a much higher rate of lung cancer than others.
E.4. Which radioactive materials cause lung cancer among miners?
Before World War II, it had been established that radon gas, rather than uranium ore dust, was the cause of lung cancer among underground miners. This conclusion was reached by comparing the miners with other workers who breathed radioactive dust but got almost no lung cancer. It was confirmed by experiments with animals.
Scientists were baffled as to why this alpha-emitting gas, radon, was such a powerful cancer-causing agent. It seemed much more damaging than other alpha emitters such as those found in the ore dust. The mystery went unexplained for more than a decade.
In the 1950s the mystery was partially dispelled when it was pointed out that the radon gas, hovering in the stagnant air of the mine, produces radioactive decay products called "radon progeny" (or, formerly, "radon daughters"). These solid radioactive byproducts, produced a single atom at a time, hang in the air along with the radon gas. When radon gas is inhaled, the radon progeny are also inhaled, resulting in a much larger dose of alpha radiation to the lungs than would be delivered by the gas alone.
E.5. Have uranium miners in North America also suffered from excess lung cancer?
When uranium mining began in earnest in the 1940's, first to supply uranium for bombs, and later for nuclear reactors, the evidence from Schneeberg and Joachimsthal was ignored. In the U.S., Navajo indians were sent into the Colorado uranium mines and exposed to levels of radon (the gas and its progeny) every bit as high as those recorded in the German and Czechoslovakian mines, with equally tragic results. In Canada, large excesses of lung cancer deaths occurred among the Newfoundland fluorspar miners, who began work in the 1930s, as well as among the uranium miners of the Northwest Territories, Saskatchewan and Ontario, who started mining in the 1940's and 1950's. Although radiation exposures in Canadian mines were less than those in American mines, significant increases in lung cancer deaths still occurred.
E.6. Are there higher rates of lung cancer among uranium miners today?
In 1976, an Ontario Royal Commission -- the Ham Commission -- found that 81 Canadian uranium miners had died from lung cancer. That was twice as many as expected. By the end of 1977, the number had risen to 119; by the end of 1981, the toll was 174; and by the end of 1984, it was 274. A 1980 report from the British Columbia Medical Association said that we must anticipate "a gradually-flowering crop of [radiation-induced] cancers" among the uranium mining population. There are many current research studies of hard rock miners exposed to radon and its progeny in Europe, the U.S. and Canada, all showing clearly increased lung cancer rates. The amount of cancer is dependent on the radiation exposure of the miners; the higher the exposure, the greater the number of cancer deaths. Significant increases in lung cancer due to radiation have been observed in both smokers and non-smokers.
E.7. Are the current levels of radiation exposure for miners considered safe?
There is no scientific evidence to indicate that there is any safe level of exposure to radon. Virtually all of the evidence points in the opposite direction. The only prudent assumption consistent with the evidence is that any exposure to radon will cause a proportional increase in the incidence of lung cancer. This conclusion has been echoed by every major report on the subject since the late 1970s.
In the early 1980s, an independent scientific study on the risks of radon was published by the Atomic Energy Control Board (AECB -- the body that sets standards for radiation exposure in Canada). This study, known as the Thomas/MacNeill Report, reviewed all available evidence from several countries. It concluded that the risks are very high.
If uranium miners worked at AECB's maximum permissible level over their entire working lifetime, the Thomas/MacNeill Report found that the lung cancer incidence would likely quadruple. Instead of 54 lung cancer deaths per 1000 males, the Ontario average, there could be close to 200 lung cancers per 1000 -- that is, one in five.
The 1980 report published by the British Columbia Medical Association (BCMA), already mentioned, called the AECB "unfit to regulate" because of the health risks it permits. No other industry, says the BCMA report, allows a cancer-causing substance in the workplace at anything close to the doubling dose for cancers in humans.
E.8. Can the health dangers be alleviated by using more miners for shorter times?
The Ham Commission warned that using more miners for shorter times, without reducing the total exposure to inhaled radon, will not reduce the number of cancer victims. If anything, it could increase the number of excess lung cancers.
The Ham Commission Report, the BCMA Report, the Thomas/ MacNeill Report, and the 1988 BEIR-IV Report (by the U.S. National Research Council) have all pointed out that at lower radon exposure levels the number of cancers caused per unit dose may actually increase. In other words, spreading the same total dose out over a larger population, so that each individual gets a smaller dose, may increase the total number of cancers caused. The BEIR IV Report observes that this phenomenon is well-known for laboratory animals, but is less clearly established in the case of human populations.
Read more:
http://www.ccnr.org/nfb_uranium_2.html#E.1.
http://www.nfb.ca/film/Uranium#
