Fallout From Chernobyl Not Global Threat, Scientists Say

The Soviet nuclear reactor accident at Chernobyl vented amounts of long-lived radioactivity comparable to that released by all the atmospheric nuclear weapon tests since the dawn of the Atomic Age, but that poses no serious worldwide health hazard, scientists at the Lawrence Livermore Laboratory reported Tuesday.

The conclusion is based on study of the amount of cesium-137 released by the explosion and fire at the Chernobyl nuclear power plant about 60 miles from Kiev in the Soviet Ukraine.

It concluded that despite serious effects in the Soviet Union and Eastern Europe near the plant, no major global health danger is likely to result from the accident.

Cesium-137 is among the longest lived of radioactive isotopes, and thus has a greater potential for adverse health effects. Cesium-137 has a half-life of 30 years, meaning that it takes 30 years for half of the radioactive atoms to decay into non-radioactive form and in large enough doses has been associated with cancer.

Useful Comparison

Lynn R. Anspaugh, a Livermore biophysicist who is part of a study team examining the accident, discussed the findings with reporters here Tuesday. He said the comparison with nuclear weapons tests was useful as a measurement of the possible impact on human health of the Chernobyl accident.

The approximately 430 atmospheric nuclear weapons tests conducted since 1945 by the United States, the Soviet Union, France, China and other nations, released “thousands of times” more total radiation into the atmosphere than did the Chernobyl accident, but most of that radiation consisted of short-lived radioactive isotopes that disappeared completely in periods ranging from a few days to a year, Anspaugh said.

“The dose from cesium-137 from atmospheric nuclear weapons was quite low,” Anspaugh said, “and since that had no readily measurable effect on human health, then we would not expect the Chernobyl event to produce any kind of disaster.”

Anspaugh is a member of a team, headed by Marvin Goldman of UC Davis, appointed by the U.S. Department of Energy to examine the potential environmental effects of the April 26 Chernobyl accident, the worst peacetime nuclear disaster in history. Anspaugh presented the committee’s initial results last week at a symposium in Saratoga Springs, N.Y.

Thirty-one people died as a result of the accident, about 200 are still hospitalized, and 135,000 people were evacuated from the area around the accident site.

Anspaugh said the group at Livermore had focused on cesium-137 since it was first detected on filters in Finland the day after the accident. They chose it because it was the only radioactive isotope present in significant quantities that would persist for a long period in the environment.

Furthermore, Anspaugh said, much was already known about the distribution and effects of cesium-137 released during atmospheric testing.

50 Million Curies

Theoretical physicists at Livermore estimated that between 1 million and 6 million curies of cesium-137 were released from the burning Chernobyl reactor. They estimated the total radiation release at about 50 million curies.

Official Soviet reports, in contrast, have estimated that 1 million curies of cesium-137 were released and that the total radiation release was only 20 million curies.

The Livermore lab has consistently reported higher levels of radiation released from the accident than have the Soviets. Both estimates are based on computer models of the fire in the reactor core and the resulting venting of radioactive particles and gas, rather than actual measurements of radioactive elements in the air.

One 20-kiloton nuclear bomb releases about 4,000 curies of cesium-137, Anspaugh said. The total amount of cesium-137 released in all atmospheric tests, Anspaugh said, was between 4 million and 10 million curies.

According to the United Nations Scientific Committee on the Effects of Atomic Radiation, the cesium-137 released by atmospheric testing was adequate to expose everyone in the Northern Hemisphere to about one rad of radiation--an amount equivalent to 6 years worth of so-called “background exposure.”

Background exposure to radiation, typically about 0.16 rads per year, comes from every day exposure to cosmic rays, medical X-rays, and other natural radioisotopes in the environment.

Calculated Exposure

The calculated exposure from cesium-137 released by Chernobyl would thus be about 0.5 to 1 rad.

“That is a very small amount of radiation in terms of trying to use a standard model to predict health effects,” Anspaugh said, “and almost certainly the health effects will not be measurable within a global context.”

Anspaugh conceded, however, that the health effects could be more serious in the Soviet Union and Eastern Europe, where individual exposures were higher.

Nonetheless, he added, “I think the most severe impacts that we can readily identify from the accident were the 31 people who died and the several hundred who were seriously injured.”