The long view

2019-03-07 09:11:10

By Matt Walker RUSSIAN and German researchers who have compiled a register of people exposed to the fallout from Soviet nuclear weapons tests say it could greatly improve our understanding of the effects of radiation. More than 450 nuclear devices were exploded at the Semipalatinsk nuclear test site in Kazakhstan between 1949 and 1990, according to the Russian Federation’s Ministries of Atomic Energy and Defence. Of these, around 116 were atmospheric detonations conducted between 1949 and 1962. The test site closed in 1990. The prevailing winds carried most of the fallout to the Altai region, northwest of the test site. Because residents were not warned about the tests, no protective measures were taken. People in certain towns in the region received an estimated total radiation dose of 1.5 sieverts from the first test alone. By comparison, European residents receive an average of 2.5 millisieverts each year from background radiation. Russian scientists led by Evgeny Zaitsev at the Institute of Regional Medico-Ecological Problems in Barnaul used census documents and school and medical records to track the exposed residents. The task was complicated by people migrating from the region and changing names, but since 1992 the researchers have traced the records of almost 40 000 people from 53 settlements. Records of people who lived in unexposed areas, or who moved to Altai following the contamination, are included as control groups. But the researchers have excluded people whose health may have been affected by other factors, such as working in industrial centres in the area. Medical records have been stored on a separate database for cross-referencing. To begin studying the risks of diseases such as lung cancer, the researchers have already conducted follow-up checks on 40 per cent of the people registered (Radiation and Environmental Biophysics, vol 38, p 207). “Studies based on such data may help to reduce uncertainties in our knowledge of radiation risk,” says Susanne Bauer of the Institute for Radiation Hygiene in Oberschleissheim, Germany, who is advising the Russians on how to evaluate the health and radiation dose data. She points out that our present knowledge is mainly based on one-off, short-term doses following the Hiroshima and Nagasaki atomic blasts. Studies of nuclear workers give some idea of the effects of long-term, low-dose exposure, but risk estimates may be flawed for exposures that vary over time, she says. Shunichi Yamashita of the Atomic Bomb Disease Institute at Nagasaki University agrees. “[The register] is very important in investigating low-dose exposure effects and in re-evaluating the standard criteria of radiation safety based on the Hiroshima and Nagasaki data,