Soviet-style secrecy has a long half life as far as radiation is concerned, and it is endangering lives. Tim Cornwell reports

Under President Bill Clinton, the US government has been busy investigating human radiation experiments conducted during the Cold War - from mentally impaired children fed radioactive isotopes with their cereal to prisoners who volunteered to have their bodies radiated. Most of those experiments, while their medical ethics were questionable and their subjects usually socially or physically vulnerable, proved relatively benign. But with American help the former Soviet Union is also returning to some old ghosts of its own.

This April marks the tenth anniversary of Chernobyl, the world's worst nuclear power accident, from which fall-out has been detected as far afield as Sweden and Quebec. But a team of Russian and American scientists has been quietly delving into a different chapter of nuclear history, when tens of thousands of people were exposed to chronic doses of radiation from the Soviet Union's first nuclear weapons plant.

Their work, though it is in the early stages, could shed light on one of the enduring mysteries of radiation research. A British scientist's study of children living near the Sellafield nuclear plant ten years ago found a higher than usual incidence of leukaemia, yet researchers have since largely failed to reproduce or explain its conclusions. Scientists believe the Russian experience of long-term radiation exposure, particularly among children, could provide some answers.

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In 1948 the Soviets began construction work on a military-run plant to produce plutonium for atomic weapons. It was called the Mayak Production Association. In the southern Urals about 2,000 miles southeast of Moscow, it was in an area of lakes, forests, and mountains, which was also heavily industrialised. With the city of Chelyabinsk at its centre, it is now regarded as the most radioactively contaminated region in the world, thanks largely to the Mayak plant.

From 1949 to 1967, some 76 million cubic metres of nuclear waste water, laced with strontium-89 and strontium-90 as well as caesium-137, were dumped in the local river system. There were about 124,000 Russian, Tartar and Bashkir people living in villages along the Techa and Iset rivers. They were exposed to radiation externally by water used in their gardens and their drainage systems, and internally by drinking the water and washing their food in it. It took several years before the authorities realised they were receiving very high doses of radiation and wholesale evacuations began.

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Radiation contamination continued, however. In 1957, the same year as the Windscale (later Sellafield) accident, high-level waste in a liquid storage tank in the area exploded, spreading radiation an estimated 200 kilometres away. There were also regular releases of radioactive gases into the air. Wind blowing across dried silt in the heavily contaminated Lake Karachay, also used as a dumping ground, helped distribute radioactive particles. And tens of thousands of workers at the nuclear complex who lived at Chelyabinsk, and a second closed city, were exposed to plutonium.

In 1994, the US and the Russian Federation agreed to fund a joint research effort into the health effects of radiation contamination. Since then a steady flow of US scientists, ranging from cancer specialists to researchers at the celebrated Lawrence Livermore National Laboratory in California have been making the journey to Chelyabinsk. The Russians have presented some of their own findings in international forums like the recent American Association for the Advancement of Science meeting in Baltimore. The project has drawn in nearly 50 experts on both sides.

Hiroshima and Nagasaki left plenty of evidence on the effects of sudden exposure to high levels of radiation. The Chelyabinsk area had large populations exposed to lower doses over a long-term period, a missing link in radiation health research, said Elaine Gallin, of the US Department of Energy, which is playing a leading role in the joint US-Russian programmes.

"The point is to have a much more accurate estimate of the risk for workers in the nuclear industry, in clean-ups and near waste sites," she said.

While worldwide production of plutonium has dropped sharply with the end of the nuclear arms race, the reprocessing of nuclear waste and spent reactor fuel still creates real risk of plutonium exposure for people working at nuclear plants and living nearby.

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Radiation is clearly associated with leukaemia, thyroid problems and breast cancer. But there are many questions about the other health effects, and about the different risks for men and women, and infants in the womb. About a quarter of the workforce inhaling plutonium traces at the Mayak plant were women, far more than in the nuclear industry in the West at the time. And nowhere in the US were so many men or women exposed to powerful doses of radiation over such a long period. Though contamination occurred at some US bomb-making sites, it tended to be in underpopulated areas in western states.

For 30 years, Russian scientists in the Urals Research Centre for Research Medicine have been studying the victims, but their results were kept largely secret. In the Soviet days they were allowed only to publish in a few secret scientific journals, and westerners heard only rumours of what had happened. Slowly, information is seeping out.

Mira Kossenko, from the centre, told the recent AAAS meeting that chronic radiation sickness was suspected among villages on the Techa as early as 1951. The symptoms were similar to chronic fatigue syndrome: patients complained of tiring easily, of general weakness, headaches, and dizziness; of memory loss, insomnia, and nausea. Over time, they suffered higher than normal death rates from cancer and leukaemia. British researcher Martin Gardner's 1986 report on the rates of leukaemia in children living round Windscale hypothesised it was due to their fathers being exposed to radiation while working at the plant.

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In the US researchers are currently attempting to duplicate his methods by identifying children suffering from leukaemia and other forms of cancer in communities near nuclear plants in Idaho, Washington state and Tennessee. They are then tracing back to see whether and when the childrens' parents worked at the plant.

And in the Urals, there are plans to study the children of the workers in Mayak. Of 1,479 workers exposed to plutonium traced in one recent study, 105 had died of lung cancer, twice the rate for a control group.

Amid the talk of growing cooperation between US and Russian colleagues, with continued political instability there remains the fear of a return to the old secrecy in a region where the influence of the KGB and its successor services are still strongly felt. One US researcher was in the area recently but not allowed to visit the plant; he had applied for permission two months before, but was told that the required notice was three months.

"There is a certain urgency to get the information out as soon as possible because the openness may end," said Hoffman. "One never knows what is going to happen."

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