For the past 60 years, the world has had only one response to radiation – fear. The atom bombs dropped on Hiroshima and Nagasaki followed by four decades of the cold war with the threat of nuclear obliteration have seen to that. The idea of radiation as a killer is lodged firmly in the public mind. It takes only a train-load of nuclear waste – one travelling from France to Germany drew 3,000 protesters this month – to spark another scare. There is one thing everyone knows about radiation: avoid it at all costs.
But, to quote the subtitle of the classic Peter Sellers movie Dr Strangelove, is it time for us to stop worrying and learn to love (radiation)? Some scientists think so, and there is accumulating evidence to back their view.
Earlier this month, Dr Bob Bury, a consultant radiologist at Leeds Teaching Hospitals, set out the evidence in a lecture at London's Royal Society of Medicine entitled "Stop worrying – radiation is good for you". As a former radiation protection spokesperson for the Royal College of Radiologists and the author of a public information leaflet on radiation hazards, his mission, he says, is to restore perspective to the radiation debate.
We know radiation destroys living things at high levels – on that there is scientific consensus. What about at low levels? Conventional thinking is that it is still damaging, but less so. For 60 years, the official view has been that there is a linear relationship between the amount of radiation exposure and the damage done. Some scientists question this view, however, and suggest that radiation exposure actually follows a J-shaped curve, with small amounts conferring benefit up to a threshold beyond which it starts to be damaging.
One striking piece of evidence for this comes from radiologists themselves. They spend their professional lives exposed to radiation, in the form of X-rays and computed tomography (CT) scans, so you might expect them to have higher rates of cancer. But they don't. They have less cancer and they live longer than physicians in other specialities.
With modern safety measures, the actual dose received by radiologists is only slightly higher than for the general population. But that may be enough to give them an advantage. Sir Richard Doll, the leading Oxford epidemiologist who first linked smoking with lung cancer in the 1950s, published a study of British radiologists in 2003 which showed that those who entered the profession between 1955 and 1970 had a 29 per cent lower risk of cancer (though this was not statistically significant) and a 32 per cent lower death rate from all causes (which was statistically significant) than other physicians.
A similar study in the US compared workers servicing conventionally powered and nuclear-powered ships. Significantly lower death rates were found in the nuclear workers compared with the others.
So how could radiation have a beneficial effect? There is good scientific evidence that while high doses destroy cells, low-dose radiation stimulates the DNA to repair mechanisms that are essential to maintaining cells throughout the lifetime of the organism. Low-dose radiation is also thought to lower the number of free radicals in the cell, substances which damage DNA. In addition, radiation stimulates apoptosis – the process which causes damaged cells to self-destruct and die before they can become malignant and cause cancer.
The idea that small doses of radiation may be good for us is known as radiation hormesis. If proved, it would have major implications for policy. "It would mean," Dr Bury says, "that the radiation protection industry may be depriving radiation workers and the public of this protective effect by setting dose limits that are too low."
Among the most prominent proponents of the theory was Professor John Cameron of the University of Florida, who died in 2005, the same year a paper summarising his views was published in The British Journal of Radiology.
He observed that billions of our cells are bombarded daily by natural background radiation, much of it from the radioactivity we carry naturally in our bodies, and yet despite this huge amount of radiation damage, cancer is a disease primarily of the elderly.
"It is reasonable to assume that our very early ancestors solved the problem of cellular repair billions of years ago and that we now have highly efficient repair mechanisms," he wrote.
He suggested that low-dose radiation might function as an "essential trace energy", similar to trace elements in the diet which, though toxic in large amounts, were essential to health.
Evidence for this comes from the cancer map of the US. The annual level of natural background radiation is more than three times higher in the Rocky mountain states of Idaho, Colorado and New Mexico than in the low-lying Gulf Coast states of Louisiana, Mississippi and Alabama. Yet the cancer death rate is higher in the Gulf states.
So convinced was Professor Cameron of the beneficial effects of low-level radiation that he argued there was now ethical justification for a clinical trial. He proposed seeking volunteers over retirement age in the Gulf states, where background radiation was low, half of whom would be given a box containing a radioactive source to keep under their beds. After 10 years, cancer rates in the "treated" group – those given the boxes – and "untreated" groups could be compared – and it was Professor Cameron's expectation that cancer rates in those exposed to the radioactive boxes would be lower.
The idea is too radical ever to win ethical approval – and would probably struggle to find volunteers, such is the public fear of radiation. But the proposal stands as a challenge to conventional thinking.
Conventional thinking needs challenging because it is often driven by irrational fear. The public loathes the nuclear industry because of its links with the atom bomb, and fear persists despite the opportunities the industry offers for producing clean energy in the era of climate change.
Distrust of the nuclear industry reached a pitch in the 1980s over revelations about the discharge of low-level radiation into the sea by the Sellafield nuclear reprocessing plant. The government responded by ordering the installation of an actinide removal plant, which opened in 1994. But this resulted in a negligible reduction in the population dose at a cost of £3m per man-Sievert (a measure of radiation).
This decision was ill-judged in two ways. First, the low-level radiation discharged by the plant might have been doing some good. Second, spending even a fraction of the money on re-equipping X-ray departments at the time – a much bigger source of radiation exposure to the public – could have halved the population dose at £140 per man-Sievert.
Today, the nuclear industry contributes around 0.2 per cent of the total annual population dose, a tiny fraction of the 50 per cent delivered by medical X-rays and imaging (CT scans). The growth in the use of CT scans has worried radiologists – especially when offered by private companies with an incentive to increase usage. Medical imaging is the biggest man-made source of radiation and thus offers the greatest potential for reducing the population dose.
On the other hand, it is also an essential aid to diagnosis of everything from broken bones to cancer. Dr Bury says: "When I trained in surgery in the 1970s, nearly every list involved a laparotomy [exploratory operation], which often turned out to be a wasted procedure. Now no surgeon opens a chest or abdomen without knowing exactly what they will find."
Since 2000, radiation protection legislation has been tightened up and British patients, unlike those in the US, should not be receiving unnecessary doses. The fear, however, remains.
How different from the 1920s, when "radium water" – supposed to stimulate the endocrine system – was marketed as a cure for almost every conceivable disease, including impotence, rheumatism, insanity and gout. Until Eben Byers, socialite, champion golfer and son of wealthy US industrialist Alexander Byers, began taking it for an injured shoulder. When he died in 1932, aged 51, the Wall Street Journal headline read: "The radium water worked fine until his jaw came off".
That marked the beginning of the great radiation scare which has lasted to this day. Now may be the time for a revision.