Authors: Joan Smith
The decisions about permitted levels of exposure were taken by Penney and David Barnes, the founder of the health physics branch at the Atomic Weapons Research Department at Aldermaston. During the Royal Commission hearings in London, Peter McClellan, the barrister assisting the commission, asked Barnes if he had known the limits chosen involved a slight risk. âA very slight risk was regarded as acceptable,' Barnes replied. âWe all thought the doses we were receiving were innocuous.'
By the time the British tests were drawing to a close, in 1958, the ICRP had recognized that its recommended limits were too high. In 1959, it published new limits, the principal change being a reduction in the annual amount of radiation a worker could be exposed to from 150 millisieverts to 50. Effectively, this limit has been in force in the British nuclear industry ever since.
Most of the people who now work in the industry get doses well below the annual limit. The average annual exposure in nuclear power stations like Sizewell A and Dungeness is 5 millisieverts per worker. But at the dirtier end of the industry - the nuclear reprocessing plant at Windscale, in Cumbria - it is nearer 30.
How do these figures compare with the doses received by participants in the British bomb tests? Adam Butler, the junior Defence Minister, has given a detailed breakdown of official records of what the veterans received. It suggests that the vast majority of them were exposed to considerably
less
radiation than people working in the nuclear industry today.
Twenty thousand British servicemen and civilians took part in the tests. Of these, the government says 15,000 were not exposed to radiation. It has records of 6,000 incidents in
which the remaining 5,000 men did receive doses of radiation.
The amounts these men got are very low, according to Butler's figures. Fewer than thirty men got a dose higher than 70 millisieverts. These were scientists like James Hole, from AWRE, who got 170 millisieverts when he volunteered to go into the bomb crater soon after the second Mosaic test.
Less than 150 men got between 20 and 70 millisieverts. Five hundred got doses between 3.5 and 20. About 1,500 got less than 3.5 millisieverts. The remaining records of exposure, which show 4,000 occasions on which men were exposed, do not give detailed readings: they establish that exposure took place, but the amount was too small for the equipment used to measure radiation to register it accurately.
The government says exposure at these levels is too small to produce a significant increase in cancer levels. But what is the evidence about the effects of low-level radiation? In fact, the history of radiation protection from the 1950s to the present day has been one in which critics of the nuclear industry have repeatedly argued that the risks of low-level radiation are much greater than the industry admits. Although the controversy has not been resolved, some studies in favour of this hypothesis which were angrily rejected in the 1950s have now won wide acceptance in the scientific community.
Dr Alice Stewart, the epidemiologist who carried out an initial survey of the Christmas Island veterans in 1983, has played a key role in identifying the hazards of low-level radiation. In 1955, as head of the Department of Preventive Medicine at Oxford University, she embarked on a study to find the cause of a sharp rise since the war in the number of children contracting leukaemia.
She discovered that X-rays given to pregnant women were the culprit. She published the results of her work in 1958: it suggested that children whose mothers had had X-rays during pregnancy were
twice as likely
to develop cancer before the age of ten as children whose mothers had not been X-rayed. If the X-ray was given in the first three months of pregnancy, the Oxford study also showed, the child was ten times more likely to develop cancer than if it happened towards the end.
At the time, Stewart's work was challenged. Today, it is so widely accepted that major changes have been made in the use of X-rays during pregnancy. In 1970, Stewart published a follow-up to the Oxford study. It demonstrated a direct relationship between the dose of radiation received by the foetus and the chance of getting cancer. Doubling the number of X-rays also doubled the risk. Significantly, the dose of radiation from an X-ray in the 1960s was only 2 millisieverts.
Alice Stewart's work on the effect of X-rays on the foetus has been complemented by a large-scale study into their effect on adults in the US. In the 1960s, the American scientist, Dr Rosalie Bertell, began work on data from the Tri-State Study, a massive investigation into the health of sixteen million adults in New York State, Maryland and Minnesota. The data included details of each person's life history, including their occupations, where they lived and the illnesses they had suffered.
Before working on the study, Bertell had given little thought to radiation. She had originally trained as a mathematician, but joined a closed order of Carmelite nuns, where she was expected to perform backbreaking physical labour. After an early heart attack, she was advised to join a teaching order, where less physical strength would be required of her. She joined the Grey Nuns of the Sacred Heart and returned to academic work, particularly in the field of the application of maths to medicine and biology. This was exactly the kind of work she was expected to do on the Tri-State Study.
The conclusions she drew from analysis of the data over ten years turned her into a passionate anti-nuclear campaigner. She noticed that the people who suffered from leukaemia were those from wealthy backgrounds with access to private medical care -and X-rays. She also noticed that these people were suffering from a particular sort of leukaemia usually associated with old age very much earlier in life than expected.
Bertell's work, like Stewart's, has brought about changes in the use of X-rays for diagnostic purposes - hospitals in the US use them much more cautiously as a result. But evidence from the effects of X-rays is far from being the only source which suggests low-level radiation is dangerous. In the 1970s, Alice Stewart was
asked to go to the US to help analyse the results of a massive study of the health of workers at one of the longest-running nuclear plants in the world - the Hanford works, near Richland, in Washington state.
The Hanford plant was one of the installations set up during the Second World War to carry out work for the Manhattan Project. During the war, its job was to produce plutonium for the bomb; it is now a huge site which houses various types of nuclear reactor, as well as storage tanks for nuclear waste. In 1965, the American nuclear regulatory body, the Atomic Energy Commission, asked Dr Thomas Mancuso, of Pittsburgh University, to look at the health of workers at the Hanford plant.
In 1974, while Mancuso was still working on his study, evidence of a high cancer rate among the Hanford workers was published by Dr Sam Milham, Epidemiology Director of the Washington State Health Department. Milham found there was a higher death rate from certain cancers - cancer of the pancreas, and multiple myeloma, a rare type of bone cancer â among Hanford workers than there was among other industrial employees in the area.
Mancuso's work started to show a similar pattern among the Hanford workers. Suddenly, the US government withdrew his funding and transferred the study elsewhere. Fortunately, Mancuso had kept copies of the data and was able to get funding from the independent Environmental Policy Center in Washington DC. In 1976, he asked Alice Stewart and one of her colleagues at Birmingham University, Dr George Kneale, to help analyse the data. Their initial findings were published in 1977, followed in 1978 by an updated version of the study.
The 1978 report was based on an examination of death certificates for more than 5,000 people who had worked at Hanford over a period of thirty-three years - 1944 to 1977. It found elevated cancer rates among those workers who, according to plant records, had been exposed to radiation. The doses they received were very low - nearly three-quarters had been exposed to less than 20 millisieverts.
Although this study confirmed Milham's earlier work, it provoked a fierce controversy. It is easy to see why. The Hanford
study suggested that the ICRP's recommended limit for radiation workers - 50 millisieverts per year - underestimates the risk by at least ten times and possibly as much as thirty times.
This is certainly not the sort of thing the nuclear industry wants to hear, as Dr Rosalie Bertell has pointed out. âThe large number of criticisms of the Hanford worker analysis seems to be related more to its perceived political importance to the foundation of the whole nuclear industry than to its scientific merit.'
Another American study published at the same time as the Hanford findings showed high cancer rates among nuclear workers. Dr Thomas Najarian, of the Boston Veterans Administration Hospital, looked at death certificates for nearly 2,000 workers at the Portsmouth Naval Shipyard, in New Hampshire. He found that their death rate from cancer was twice the national average.
In 1980, yet another significant report was published. It examined the health of more than 3,000 men who participated in an American atom bomb test, code-named Smoky, which took place at the Nevada test site in August 1957. Dr Glyn Caldwell, of the Center for Disease Control in Atlanta, Georgia, reported that the incidence of leukaemia among the men was nearly three times higher than it should have been. Records of exposure were available for eight of the nine men; they all received less than 30 millisieverts. The mean dose for the eight men was only just over 10 millisieverts.
The Smoky test study seemed to provide valuable corroborative evidence of the dangers of low-level radiation, and of the claims of both the American and British veterans. But three years later, Caldwell inexplicably withdrew support from his own study. Dr Rosalie Bertell found herself in the unusual position of defending a study against its author: she considers the Smoky study valid, and says there have been no new findings which necessitate rejection of it.
These studies, and others, suggest the ICRP has consistently underestimated the risk from low-level radiation. A committee set up by the prestigious US National Academy of Science reported on the risk in 1980 and came up with figures that put the risk up to five times higher than the ICRP's estimate. Even then,
the committee warned that its own figures âshould in no way be interpreted as precise numerical expectations. They are based on incomplete data and involved a large degree of uncertainty, especially in the low-dose region.'
The committee's own chairman, Professor Edward Radford, of Pittsburgh University, disagreed with its findings. He published a minority report, arguing that the committee was still underestimating the risk. In April 1983, Radford told me he expected a âcancer epidemic' among nuclear workers unless limits are lowered drastically. They have not been.
Radford came to London in February 1985 to give evidence to the Royal Commission into the British atom bomb tests. He described his research into the health of people in Canonsburg, Pennsylvania, a town still polluted by radioactive waste from its part in the Manhattan Project. During the war, Canonsburg was the site of a factory which processed uranium for the atom bomb; large quantities of radioactive waste are buried beneath the town. The US government has already offered out-of-court settlements to more than thirty residents who claim their health has been affected by radiation.
But Radford's research in Canonsburg threw up one particularly alarming piece of evidence about low-level radiation. âTo my surprise, we found that in Canonsburg there was a significant number of radiation-induced thyroid abnormalities,' he told the Royal Commission. âI was surprised because the figures said these people had been exposed to radiation in the order of only two or three times natural background.' The thyroid is known to be particularly sensitive to radiation. But the Canonsburg cases appear to have been caused by startlingly low levels of radiation.
In the 1980s, evidence of health problems near nuclear installations in Britain began to mount. Clusters of leukaemia have been reported among people living close to nuclear power stations. One of these is next to the Sizewell A power station, in east Suffolk. A high incidence of leukaemia and cancer of the lymph glands has been noticed among children living near the Oldbury and Berkeley power stations, in the West Country. People living near these plants are exposed to very low levels of radiation.
But the most serious and sustained allegations centre on the reprocessing plant at Windscale, in Cumbria. In November 1983, Yorkshire Television reported high levels of cancer among children in villages near the plant. The government set up an inquiry, under Sir Douglas Black; as it began work, I reported in the
Sunday Times
that doctors were investigating high levels of leukaemia on the west coast of Scotland, right in the path of tides from Windscale. I also reported that doctors in Fleetwood, in Lancashire, to the south of Windscale, had found an unexpectedly high rate of bone-marrow cancer in the area.
When the Black report was published, in July 1984, it proved to be a rather curious document. It confirmed the high incidence of leukaemia in villages near Windscale but shied away from linking it with the plant. Black himself even offered the public a âqualified reassurance' that the problem had not been caused by Windscale.
The Black report is seriously flawed. First, as James Cutler of Yorkshire Television has shown, it underestimated the cancer rate close to Windscale. Nearly half the cases of childhood cancer in Seascale and nearby villages were left out of the report's analysis. This fact undermines the report's conclusion that the childhood cancer rate in the area is âunusual but not unparalleled'.
Cutler has also demonstrated that the inquiry miscalculated the dose of radiation received by local children. A meeting held at the DHSS since the publication of the report was told that the inquiry had made an incorrect assumption about the dose to the bone marrow, an error which might mean children living near the plant had got much higher doses of radiation than the Black inquiry assumed.