Wednesday, June 29, 2011

Ron Smith: The Effects of Radiation

Nearly thirty years ago an extraordinary accident occurred in a steelworks in Taiwan, as a result of which, a substantial batch of recycled steel became contaminated with radioactive Cobalt-60 from discarded medical isotopes. The resulting steel was used in the construction of apartment buildings, businesses and schools in Taipei and its suburbs. That this had happened was not discovered until nearly ten years later, and the full extent of the radiation exposure was not realised for another ten years. Some people lived in the contaminated apartments for almost twenty years before they were finally evacuated. At about this point, serious systematic studies of the health consequences for long-term inhabitants of the apartments, and users of the schools and businesses, were undertaken by Taiwanese medical academics. They were ultimately published in the Spring 2004 issue of the Journal of American Physicians and Surgeons.

The researchers expected to find elevated rates of cancer mortality amongst the exposed population and, perhaps also, evidence of congenital malformation (‘birth defects’), amongst the 10,000 persons, who had lived or worked in the contaminated buildings for as long as two decades. They found no such effects. In fact, what they found was a population, young and old, that showed lower rates of these things. How could such a thing be?

The explanation has two parts. The first concerns the supposed adverse health effects of radiation exposure at progressively lower and lower doses. For this, the official assumption (enshrined in the standards promulgated by the International Commission on Radiation Protection) has been that, whilst the risk decreases as the dose decreases, there is no point at which the risk disappears, however low the exposure. This is called the Linear No-threshold (LNT) principle (hypothesis) and it predicts radiation effects down to the lowest levels, with a correspondingly lower incidence per capita. Calculations of this sort, based on very large ‘exposed’ populations can give rise to alarming predictions of radiation-caused deaths, such as were made in relation to Chernobyl (and are now being made in relation to Fukushima). One of the several important conclusions from the ‘Taipei’ research is that the LNT principle is fundamentally mistaken. There is a dose below which adverse health effects do not occur.

Of course, the Taipei study is by no means the only evidence that the predictions of the LNT hypothesis at low doses is not borne out by effects that are actually found. As I noted in an earlier column (May, last year), the widely predicted elevated rates of cancer and birth-defects caused by the Chernobyl event were not found by the United Nations ‘Chernobyl Panel’, when it reported twenty years later. Similarly (and, again, this was noted in the report of the Chernobyl Panel), there are very wide natural variations in the radiation exposure of persons according to where they live, and in regard to adventitious factors like medical procedures that entail radioactive isotopes, or X-rays, and the like. There is no correlation between these things and greater incidence of radiation effects.

The reason why the predicted effects at low doses are not found has to do with evolution (and this is the second part of the promised ‘explanation’). Life on planet earth evolved in circumstances of continual radiation exposure, from the radioactive rocks of the earth and from extra-terrestrial sources. Early life-forms on the planet thus evolved biological defence mechanisms, which were able to dispose of free radicals and consequent defective DNA material. In due time, human beings inherited these mechanisms. Indeed, it may be that the lower incidence of radiation effects in the Taipei study were due to the activation of these biological defence mechanisms by the elevated radiation levels, in the same way that immunisation is protective against micro-organisms by stimulating the production of antibodies. The process is called radiation hormesis.

Of course, the point of all this is that when we hear of elevated levels of radiation in the environment, as presently around Fukushima, we really need to know what the anticipated human exposure is, compared to the normal background variation, or compared to abnormal cases, such as the above (Chernobyl, Taipei, etc.). The reported levels may be within those that are not harmful, or may be even beneficial. Certainly, the evidence seems to show that the mere fact that an individual is subjected to radiation levels which are higher than (for them) ‘normal’ is not, of itself, a cause for concern, although the sudden appearance of higher radiation readings would properly trigger the search for an explanation.

The earthquake and tsunami that struck Japan on 11 March this year, caused enormous damage to infrastructure and human habitation across a wide area of NE Honshu, and killed upwards of 20,000 people. The effect of the tsunami on the Fukushima Daiichi nuclear plant was to cause extensive damage over the whole site area, including a partial meltdown in three of the six reactors and (hydrogen) explosive damage to four buildings, with a consequent release of radioactive material into the environment. Overall, the effect of the Fukushima event will have been financially catastrophic but it killed nobody and, despite very elevated radiation levels within the plant at various times, the likelihood is that no one will die as a result of radiation exposure.

Notwithstanding present sentiment in the country, nuclear power will continue to be of considerable importance to Japan (and many other countries world-wide) in the years ahead. It is therefore of considerable concern that the media commentary and consequent public response has been so out of proportion to the actual, or potential, public harm. Japan will not power a revival of its high tech industrial might by solar panels on its sky-scrapers, or windmills on its hills. It (and many other countries of the industrial world) will need to get serious about combating the continuing torrent of propaganda from anti-nuclear activist groups. Otherwise it will face a difficult future.

5 comments:

Kiwiwit said...

Richard A Muller discussed the LNT theory in his book Physics for Future Presidents - and pretty much rejected it. The problem with the media hysteria over Fukishima is it is leading to ill-conceived policies like those of the German government to decommission all nuclear power plants. As this article discusses, http://environmentblog.ncpa.org/germany-finds-going-green-is-tough-going/ , the Germans are finding their policy is not so smart.

Anonymous said...

I am a metal mining engineer, and have worked underground in a many mines around the world. I have spent time in Cornwall, U.K., which is well known to have a high background radioactive presence on surface, far more than many industrial applications,are allowed to have. Sellafield, and all reactors included.

Interestingly I have also worked at Elliot Lake, in middle Ontario, once home to Canada's uranium industry where underground radiation is a well known feature of mining there. Many thousands of miners have worked underground with no effect whatsoever on their health, compared to with smoking tobacco for example. In my opinion it is a well prepared depository for all the worlds reactive waste, shipped along the St Lawrence Seaway to Port Hope, then onto the CNR railway to Elloit Lake, and then taken 1500m deep underground using the shafts and stopes whence the ore was once mined to power the worlds nuclear reactors. God put it there, and politicians stop it from returning as a waste product.

Interesting is it not. We have also overlooked the fact that the globe in the sky, the Sun, is a highly radioactive source which radiates the earth in huge daily radiation. Of course that's natural - so that's alright then. Hardrockminer

Brian said...

The recent accident in Japan played into the hands of the Greens, and those whose aim in life seems to be to protect us all from life's mishaps. They of course, know exactly what we the public need to live in safety.

Basically it is a Weapon, a Weapon of FEAR, one can trace Fear throughout history. Poor old Columbus had to endure years of "If you sail West the ship will fall off the edge of the world" or as Galileo found to his cost "That the earth is the centre of the universe surrounded by sun & planets.
Fear is the weapon of the protest movement, of the Green ideology, and more importantly a weapon of Government.
Yet in our modern civilization with all its benefits and knowledge we still are possessed by fear. Fear of disease, germs, chemicals the things we eat. It is as if we have been transposed back into the early Middle ages.
Dr. Smith has summarized the present public fear of radio active nuclear power, the media compounds this fear; and the political parties have waited to see how this fear has acted upon the general public. In the case Nuclear power and Global Warming, they have used this Fear to win elections.
Brian

.

Anonymous said...

Prof (Now "Sir") Paul Callaghan has strong opinions about the anti-nuke unreason. It is a pity he doesn't speak out about it, probably because he is a bit of a lefty and doesn't want to embarrass his lifelong political acquaintances in the Labour Party particularly.

Anonymous said...

One can argue at great length without coming to any conclusions on the pro and cons of nuclear power, but one thing we all agree on is the problem of disposal of nuclear waste.
Eventually science will find the way to neutralize harmful nuclear particles and until then we must err on the side of caution. The fact that so far we have not seen any dramatic after effects is mainly due to the following factors, first -- the technology used in the manufacture of protective gear appears to be adequate, second -- the public safety policies in place have distanced the population from the disaster location sufficiently to prevent any major health problem such as sever burns and radiation sickness, and third -- the withholding of reports from engineers and scientists "on site" of any serious scientific events on the site, gives everyone a sense of confidence that things are not as bad as may appear and that this event can be resolved like any engineering problem.
It is unfortunate that the effects of nuclear radiation in nearly all cases will take some time to manifest. It is now admitted by Russian and Ukranian Authorities that the population from the immediate vicinity are suffering from the effects of exposure beyond safe limits in the form of increased incidences of cancers, genetic mutations and other related problems
And the final problem, that only future generation can deal with, this is the contamination of the food chain.