<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Some ought to be interested:<div><br></div><div>Op-ed from the <i>New Scientist</i><br><br>Who's afraid of radiation?<br>03 August 2010<br>by Wade Allison<br><br>Our attitude to ionizing radiation is irrational,<br>and easing safety limits would do far more good<br>than harm, says Wade Allison<br><br>THE word "radiation" frightens people, and little<br>wonder. Ever since the cold war, the prevailing<br>view has been that ionizing radiation can do real<br>harm to us without being seen or felt - and should<br>be avoided at all costs. In fact radiation is much<br>less harmful than we feared. Given the<br>availability of carbon-free nuclear power, this<br>makes a sea change in our view of radiation rather<br>urgent.<br><br> Fear of radiation grew alongside descriptions<br>of what might happen in the event of a nuclear<br>war. In earlier decades there was genuine<br>scientific uncertainty about radiation's long-term<br>health effects, and scientists were unable to be<br>reassuring. So, driven by universal popular<br>concern, tight regulation was imposed to minimize<br>public exposure.<br><br> Since 1950, public dose limits have been<br>tightened by a factor of 150. Currently, the<br>internationally recommended limit is 1<br>millisievert per year above the natural background<br>level of about 2.5 millisieverts per year. For<br>comparison, a typical CT scan might give you a<br>dose of 5 millisieverts and a simple dental or<br>limb-fracture X-ray 1/100th of that.<br><br> Much has been learned over the past half<br>century from clinical medicine, radiobiology and<br>accidents like Chernobyl. There is no doubt that a<br>very high single dose is fatal, as the fate of the<br>initial 237 firefighters at Chernobyl illustrates.<br>Within a few weeks, 28 died, and 27 of those had<br>received doses in excess of 4 sieverts.<br><br> However, many people receive much higher<br>doses than this, albeit under very different<br>circumstances. When a cancer patient is treated<br>with radiation in a radiotherapy clinic, the<br>tumour dies after absorbing a dose of more than 40<br>sieverts. During the treatment, healthy tissue and<br>organs near the tumour get an incidental dose of<br>some 20 sieverts, which is 20,000 times the<br>recommended annual limit and at least five times<br>the dose that proved fatal at Chernobyl.<br><br> How can tissue survive this friendly fire? A<br>radiation dose is the same in principle, whether<br>received in a hospital or elsewhere. But the<br>critical point is that the therapeutic dose is<br>spread over four to six weeks, giving cells time<br>to repair the damage. Each day the healthy cells<br>receive about 1 sievert, and just manage to repair<br>themselves. The tumour cells receive a higher<br>dose, and just fail to do so.<br><br> So much for acute effects, but what about<br>longer-term ones? Very rarely, the damage is<br>misrepaired, and the resulting error may<br>eventually lead to cancer. To find out how often<br>this happens, we need to compare the lifelong<br>health data of a large number of people, some of<br>whom have received a significant radiation dose<br>and some who have not.<br><br> The nuclear bombs dropped on the Japanese<br>cities of Hiroshima and Nagasaki in August 1945<br>provide us with the data we need. About 66 per<br>cent of the original inhabitants of the two cities<br>survived to 1950, since when their individual<br>health records have been extensively studied.<br><br> By 2000, 7.9 per cent of them had died of<br>cancer, compared with 7.5 per cent expected from<br>rates found in similar Japanese cities over the<br>same period (Radiation Research, vol 162, p 377).<br>This shows that the extra risk caused by radiation<br>is very small compared with the background cancer<br>risk, and less than the 0.6 per cent chance of an<br>American citizen dying in a road traffic accident<br>in 50 years.<br><br> Not surprisingly, those who received higher<br>doses developed more cancers. But those subjected<br>to doses less than 0.1 sievert showed no<br>significant increase in solid cancers or<br>leukaemias. Nor did they suffer an increase in the<br>incidence of deformities, heart disease or<br>pregnancy abnormalities. So there is a practical<br>threshold of 0.1 sievert for any measurable effect<br>due to a single acute dose.<br><br> Given what we now know, from radiotherapy to<br>the legacy of the attacks on Hiroshima and<br>Nagasaki, it is clear that radiation safety limits<br>are far too conservative. Evidently, our bodies<br>have learned through evolution to repair or<br>eliminate damaged cells, with a low failure rate.<br>I suggest the upper limit might be reset at a<br>lifetime total of 5 sieverts, at no more than 0.1<br>sievert per month. That would be a fraction of a<br>radiotherapy dose, spread over a lifetime.<br><br> Such a revision would relax current<br>regulations by a factor of 1000. This may seem<br>excessively radical to some, especially those in<br>the safety industry who have spent 60 years trying<br>to reassure the public by regulating against all<br>avoidable sources of radiation - which, after all,<br>is what society asked them to do.<br><br> But common sense says that extra precautions<br>are most needed when we know least, and in a<br>reasoned approach to any new technology we should<br>start with a cautious limit which may be relaxed<br>later, as instrumentation improves and our<br>appreciation of it grows. The regulation of<br>ionising radiation has resolutely gone in the<br>opposite direction, driven by fear.<br><br> Changing the limits would bring practical<br>benefits. Radiation safety is a major contributor<br>to the cost of nuclear power, so any relaxation<br>should lead to big cost reductions. Given that we<br>urgently need to develop carbon-free energy<br>sources, that is hugely beneficial.<br><br> It should also lead to a more sensible<br>attitude to nuclear waste. If treated properly,<br>the quantities are small, it become harmless after<br>a few centuries, and it may be buried at moderate<br>cost. In any event, the effect of radioactive<br>waste is a small matter compared with the global<br>influence of carbon dioxide and leaked<br>hydrocarbons. We should re-examine the<br>environmental risks of radiation with the same<br>radical attitude that is required for our own<br>health.<br><br> Wade Allison is a nuclear and medical<br>physicist at the University of Oxford and the<br>author of Radiation and Reason (YPD Books).<br>He has no ties to the nuclear industry<br><br><<a href="http://www.newscientist.com/article/mg20727715.800-whos-afraid-of-radiation.html?full=true">http://www.newscientist.com/article/mg20727715.800-whos-afraid-of-radiation.html?full=true</a>><br><br>~~~~~~~~~~~~~~~~~~~~~~~ </div></body></html>