Scientists Project Cancer Fatalities : Chernobyl’s Death Toll May Run Into Thousands
Nearly a month after the Chernobyl nuclear accident, a vague outline of the disaster’s terrible legacy is emerging. Using computer projections, some scientists are predicting that thousands of Europeans and Soviets may develop cancer in the next several decades and that as many as 5,000 to 40,000 ultimately could die as a result.
According to John Gofman, professor emeritus of medical physics at the University of California, Berkeley, at least 32,900 people in Scandinavia and the rest of Europe may develop cancer, and half of them could die, as a result of exposure to radiation unleashed in the April 26 accident in the Soviet Ukraine. He also believes that as many as 23,000 Soviet citizens could die of cancer.
Separately, a more conservative set of estimates, prepared last week by physicists Thomas Cochran of the Natural Resources Defense Council and Frank von Hippel of Princeton University, predicts that at least 51,280 people in Scandinavia, Europe and the Soviet Union might develop cancer as a result of Chernobyl, but that only 5,128 would die of it.
Such projections are bound to be controversial--and will surely be debated for years to come.
Asked about the two sets of estimates, Seymour Jablon, a National Academy of Sciences public health expert, said he would be “hard put to come up with those numbers.” He conceded that Cochran and von Hippel’s estimate of 5,000-plus deaths “might not be a bad guess. But I don’t know what the doses are and I am not making any guesses myself.”
The ultimate toll may never be known, but it could well be somewhere in between the two projections, said Dr. Richard Gardiner, a radiologist and a spokesman for Physicians for Social Responsibility, an anti-nuclear war group. “My guess would have been that von Hippel’s figures would be low and Gofman’s would be high,” said Gardiner of Chicago’s Rush-Presbyterian-St. Luke’s Medical Center.
The gaps between the two sets of numbers reflect differences in methodology and in how the researchers estimated radiation exposure, upon which disease and death projections were based. The disparity between the calculations also reflects a continuing controversy over the health risks of low-level radiation exposure.
Most of the radiation levels recorded in Europe and in Scandinavia after the Chernobyl accident were fairly low. In the first days after the accident became known, for example, Sweden and Finland reported radiation levels of about 500 to 1,000 times background levels. The background level averages about 100 millirems per year, or less than one-third of a millirem per day; some scientists contend that even such background radiation--from cosmic rays and naturally occurring uranium--can cause cancer.
A radiation level of 100 times background is thus equivalent to about 30 millirems per day. By comparison, medical and dental X-rays deliver between five and 20 millirems.
Computer Simulations
Cochran’s and von Hippel’s calculations are based on computer simulations of radiation released from Chernobyl conducted by physicist Joseph Knox and his colleagues at Lawrence Livermore National Laboratory. The group assumed that half of the radioactivity in the Chernobyl reactor was released within the first six days after the accident--an assumption most scientists accept as roughly accurate. The group then used meteorological conditions at the time in computing how the radiation was distributed.
Cochran and von Hippel estimated that the land area exposed to varying levels of radiation, assumed a population density of 50 people per square kilometer and then estimated the potential incidence of benign thyroid nodules or “abnormalities,” which are caused by radioactive iodine; thyroid cancers, and other cancers, most of which would be caused by radioactive cesium.
They also relied on the 1983 so-called BEIR report by the National Academy of Sciences committee on the biological effects of ionizing radiation, which predicted about two excess cancer deaths for every 10,000 people exposed to 1,000 millirems of radiation.
Cochran and von Hippel projected that inhalation of radioactive iodine from Chernobyl would cause 24,200 thyroid abnormalities, 8,070 thyroid cancers and 478 deaths. In addition, ingestion of food and milk containing radioactive iodine would cause another 116,500 thyroid abnormalities, 30,880 thyroid cancers and 2,330 deaths, they said.
Cesium-Caused Deaths
Radioactive cesium would cause another 4,640 cancers and 2,320 deaths.
Knox and Cochran cautioned that their estimates are “very conservative.” Knox said the computed exposures could be low by a factor of 10, in which case the number of cancer deaths calculated by Cochran and von Hippel would be over 50,000.
Cochran also noted that fallout during the period beyond the six days covered by the computer calculations could further increase the projections. He noted, for example, that continued fallout of radioactive cesium could increase the number of fatalities and cancers fourfold, yielding at least 16,000 cancers and 8,000 deaths.
The number of thyroid cancers and fatalities would also grow, but not as much because of the short (eight days) half-life of radioactive iodine. Cochran predicted that the number of cancers from ingestion of radioactive iodine might rise to about 80,000 and the number of deaths to 4,000.
Many countries, however, acted to try to reduce the ultimate number of thyroid cancers by limiting public milk consumption, advising citizens to rinse leafy vegetables and making available iodine pills that act to prevent the thyroid from absorbing radioactive iodine.
Poland Acted Early
Poland, for instance, began issuing iodine tablets for children immediately after the accident was known, and other countries have used them on a more limited basis.
In contrast to the projections by Cochran and von Hippel, the calculations by UC Berkeley’s Gofman are based on measured radiation levels in selected cities most affected. That data was collected by individual countries and sent to the World Health Organization, which forwarded it to the U.S. Environmental Protection Agency.
At the request of the State Department, the EPA then calculated cumulative exposures to radiation in cities with large U.S. embassies. These readings were used by Gofman, who then assumed that they were representative of the country as a whole. When data was available for more than one city in a country, he averaged the readings.
Gofman used his own estimates of risk, which are about 17 times higher than the BEIR estimates. But his estimates are in line with more recent estimates used by the National Institutes of Health and by epidemiologist Edward Radford, who chaired the BEIR committee. Many scientists now believe that epidemiological evidence, such as studies of the survivors of the Hiroshima and Nagasaki atomic bombings, support the higher risk estimates.
For the eight most affected countries, Gofman said 89 adults and 179 children would die from thyroid cancer (as a result of inhalation). The countries are Austria, Czechoslovakia, Finland, Hungary, Poland, Romania, Sweden and Yugoslavia. There was no data to indicate the levels of ingestion of iodine through food.
Uses Different Bases
Unlike Cochran and von Hippel, who assumed that there would be about 20 cases of thyroid cancer for every fatality, Gofman used a figure of eight to calculate a total of 2,144 cancers.
For the eight countries combined, he also predicted a total of 16,004 fatalities from other cancers, and a total of 32,000 cases of cancer.
No data is available for exposures within the Soviet Union. The eight countries for which data was available represent about 40% of the area exposed to significant levels of radiation; much of the other 60% lies within the Soviet Union.
Extrapolating Gofman’s calculations to that area, it is possible to estimate a total of at least 23,000 fatalities from cancer in the Soviet Union.
To date, 13 Soviet citizens are known to have died as result of the accident and about 300 others were seriously injured.
Like Cochran and von Hippel, Gofman thinks that his estimates are conservative. Data collection in Europe was spotty, especially for the periods immediately after the accident, Gofman said.
Most scientists contacted by The Times were reluctant to be quoted about the projections. But some of them said they simply assume that there will be significant numbers of fatalities in Europe and the Soviet Union.
Support for the projections comes from a 1983 report by the British government on a similar fire and radiation release at the Windscale nuclear facility in October of 1957. That report calculated that about 33 people died of cancer as a result of that accident.
If Knox’s estimates are correct, Chernobyl released about 2,300 times as much radiation as did Windscale. If the number of cancer deaths were increased proportionately, the Chernobyl accident then could yield as many as 76,000 deaths--in the same ballpark as the calculations by Gofman.
Whether or not the predictions are correct, however, may never be known. Cancer normally kills about 165,000 people out of every million. Looking for an increase of even 40,000 deaths against that backdrop, Gardiner said, “is like looking for a few needles in a haystack.
PREDICTED CANCER DEATHS FROM CHERNOBYL LEGACY
The maps on the right are estimates of radiation released by the Chernobyl accident, based on computer calculations by the Lawrence Livermore National Laboratory. Separately, the estimates of deaths were made by physicists Thomas Cochran of the Natural Resources Defense Council and Frank von Hippel of Princeton University. Each successively larger area represents a 10-fold decrease in radiation deposition and in incidence of cancer. The map on the left is based on computations of cumulative exposure to radiation performed by the U.S. Environmental Protection Agency and based on actual measurements as reported by affected countries. The estimates of deaths were made by medical physicist John Gofman of UC Berkeley.
D = Deaths C = Cancers P = Population in millions
D = Deaths C = Cancers P = Population in millions
Austria D=143, C=302, P=7.6m
Czechoslovakia D=582, C=1191, P=15.5m
Hungary D=319, C=648, P=10.6m
Poland D=4,782, C=10,086, P=36.9m
Romania D=8,622, C=17,838, P=22.9m
Yugoslavia D=685, C=1,402, P=23m
Soviet Union/ Bulgaria D=24,400
C=52,000
P=100m
Sweden D=1,017
C=2,058
P=8.3m
Finland D=165
C=342
P=4.9m
Small
D=1,582
C=13,090
P=4m
Medium
D=2,479
C=26,430
P=44m
Large
D=952
C=11,760
P=120m
