(November 18, 2005) A new study mostly conducted by Russian scientists, with cooperation from U.S. scientists, has bolstered the findings of previous studies suggesting that no radiation dose, low or otherwise, should be considered safe.
(638.5732) WISE-Amsterdam - In the WISE/NIRS Nuclear Monitor #632, we covered the conclusions of the Biological Effects of Ionizing Radiation Report VII (BEIR VII) from the U.S. National Academy of Sciences (NAS) panel that surmised that no dose of radiation is safe for humans. Further that even x-rays may be 2-3 times more dangerous than other forms of radiation and showed that background radiation, excluding radon, is responsible for cancer incidence in 1 in 100 people, which equates to 60 million people worldwide. (See WISE/NIRS Nuclear Monitor 632.5701 "U.S. Radiation panel: no radiation dose safe")
The newly released Russian study looked at a cohort of almost 30,000 people from 41 villages along the banks of the Techa River in the southern Urals region of Russia. Liquid radioactive wastes discharged from the Mayak plant during the late 1940s and 1950s contaminated the Techa, which is fed by the artificial Lake Karachai near Mayak and flows for around 240 kilometers through rural areas of Chelyabinsk and Kurgan Oblasts.
Mayak's contaminative history
The Mayak plant, nearly 100 kilometers north of the city of Chelyabinsk began operating a nuclear reactor and plutonium separation plant in 1948. Plutonium separation is known to create vast amounts of liquid wastes and it is estimated that Mayak released some 76 million cubic meters of radioactive waste into the Techa River between 1949 and 1956; however, the largest quantities were discharged between January 1950 and December 1952. The levels of radiation (around 120 million curies), from long-lived radionuclides cesium-137 and strontium-90, were said to be 2.5 times the total releases from Chernobyl. A 1990 report by the Natural Resources Defense Council (NRDC) found that traces of the wastes could even be detected as far as the Arctic Ocean.
Apart from the dumping of radioactive wastes into the Techa, Mayak also caused other disasters. In 1957, the cooling system broke down causing one of the concrete tanks containing contaminated water to explode, releasing 20 million curies of radioactivity into the atmosphere and contaminating 23,000 square kilometers. Then ten years later, a drought exposed the bed of lake Karachai and radioactive dust was carried by a tornado over a wide area. The then Soviet authorities hid and denied the accidents for many years and when they did admit them, claimed that there had been no casualties and no long-term health effects. The people of the Techa villages swam and fished in its waters until it was finally fenced off. But once the flimsy fences had broken down and without any signage to indicate radioactive danger, villagers - often children - again returned to the riverbanks.
The first known research on radiation exposure in the Chelyabinsk region was published in the Physicians for Social Responsibility journal in 1993 and revealed an increased incident of death from leukemia among a cohort of 28,000 exposed to radiation from Mayak. It estimated that some half a million had been affected by the three contamination incidents from 1951 to 1967.
Following the various accidents some 60,000 people are believed to have been evacuated but many were relocated to remote parts of the then Soviet Union where no records were kept on most of them.
Dispensary 1, now the Urals Research Centre for Radiation Medicine (URCRM), established the cohort in 1955 in order to learn more about the effects of chronic long-term radiation exposure, from both internal and external radiation. It included people from wide ranging age groups and was made up of both sexes (60% women) with some 40% aged under 20 years old and 30% aged over 40 years old at the time of exposure and followed up on the majority of the group for 50 years. The members were people who had lived in the villages during the years of most significant discharges and originally those born before January 1, 1950 who had lived in the villages along the Techa between January 1950 and December 1952. Later the group was expanded to include people who first lived by the river between January 1953 and December 1960 but who had also been born before January 1, 1950.
Levels of strontium-90 in the teeth of the subjects were measured and whole-body counts of strontium and cesium-137 were also taken and the results showed that at least one strontium measurement for over one third of the villagers. Of the 12,732 deaths from known causes among the cohort, 1,842 of the villagers are known to have died from solid cancers (excluding bone cancer) and 61 from leukemia (excluding chronic lymphocytic leukemia or CLL). That is 14.5% and 0.4% respectively. The scientists concluded that the excess cancers found in the populations living around the Techa could be linked to the exposure to radioactivity from Mayak.
Another previous study, conducted by the International Agency for Research on Cancer in Lyon, France, looked at data from over 400,000 nuclear plant workers from 15 countries and found 6519 deaths from solid cancers and 196 from non-CLL leukemia. This, the largest study of nuclear workers ever undertaken, suggested that between 1% to 2% of deaths may be due to radiation but did fail to take smoking into account. The researchers admitted that smoking might have played a role in the increased risk of cancer, excluding leukemia, but countered that smoking could not explain all the increased risk observed. That being said, the latest Russian study does corroborate previous evidence and comes to a similar conclusion.
The International Commission on Radiological Protection (ICRP) in 1991 set dose limits for radiation workers at 20 millisieverts (mSv) per year over five years although the United States does not use these standards, instead preferring to expose workers to up to 50 mSv per year. The French study revealed an average lifetime dose of 19.4 mSv for nuclear workers while the Russian study found that the majority of villagers had received less than 50 mSv over a lifetime.
Industry has long sought to have ICRP limits increased claiming that they are over cautious but the evidence now seems to suggest that more not less caution needs to be taken.
Sources: Science, Vol. 310, Issue 5750, November 11, 2005; Radiation Research 164, p 591-601 & p 602-611 (2005) "The Techa River Cohort: Study Design and Follow-up Methods" by M. M. Kossenko, T. L. Thomas, A. V. Akleyev, L. Yu. Krestinina, N. V. Startsev, O. V. Vyushkova, C. M. Zhidkova, D. A. Hoffman, D. L. Preston, F. Davis and E. Ron; "Protracted Radiation Exposure and Cancer Mortality in the Techa River Cohort" by L. Yu. Krestinina, D. L. Preston, E. V. Ostroumova, M. O. Degteva, E. Ron, O. V. Vyushkova, N. V. Startsev, M. M. Kossenko and A. V. Akleyev; WISE/NIRS Nuclear Monitor #632, July 15, 2005; WISE News Communique #453June 7, 1996; WISE News Communique #385 January 22, 1993; WISE News Communique #374, June 25, 1992; WISE News Communique #341, November 2, 1990
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