Wednesday, June 29, 2011
Ron Smith: The Effects of Radiation
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.
at 4:48 PM