Radiation phobia and phantom risks.(Science)

IN THE SEPTEMBER Quadrant, Leslie G. Kemeny argued persuasively that nuclear energy must be reexamined in Australia, because this is power generation that does not produce greenhouse gases. On Lateline on October 18, Tony Jones interviewed James Lovelock, scientist and environmentalist from the UK. Lovelock is alarmed by the progressive increase in atmospheric carbon dioxide which now is accelerating, and almost certainly will lead to irreversible world temperature increases before the end of this century. He believes greater reliance on nuclear energy is the only alternative.

Nuclear energy has had nearly fifty years of trial, and produces energy virtually without the production of greenhouse gases. There are more than 440 reactors worldwide which provide around 16 per cent of the world's electricity. Australia has no reactors for energy production even though uranium oxide concentrates from the Ranger mine in the Northern Territory and Olympic Dam in South Australia amount to nearly 20 per cent of world production.

So what is the problem with nuclear power? In the Australian Financial Review on August 13, Lord Taverne, a member of Harold Wilson's Labour government, provided some background:

 
   Most of us assume that public policy is based on 
   evidence. Alas, not so. Why do green campaigners, 
   with the notable exception of James Lovelock, reject 
   nuclear power, which emits no greenhouse gases? 
   Because they are frightened of accidents and of 
   radiation emanating from nuclear power stations and 
   nuclear waste. Their fears of radiation are not only 
   widely shared, but they are nourished by official 
   sources and have even become official policy. 
 
      Present policies for radiation safety are based on 
   the "linear no threshold assumption", which is 
   endorsed by the International Commission of 
   Radiological Protection. This is the assumption that 
   even the smallest amount of radiation is harmful and 
   may cause cancer and genetic disorders, and that the 
   risk of harm increases proportionately with the dose. 
 
      On this basis, we should aim to avoid any 
   exposure at all. Accordingly, the standards for 
   radiation protection set by the Commission have 
   become more exacting, and the maximum exposure 
   dose declared to be safe is continually lowered. 

Many people have serious concerns about risks from low-level exposures to ionising radiation. Large sums of money are spent to reduce these perceived risks. These fears basically derive from the direct linear extrapolation of the obvious harm from radiation at high exposures to the very small, predominantly background, levels to which all people on Earth are exposed.

However, this linear-no-threshold assumption does not fit effects on human health. A J-shaped curve fits the data better. That is, a low dose of radiation seems to stimulate DNA repair and the immune system, leading to protection against the deleterious health effects of radiation at higher exposures.

This non-linearity is known as hormesis. A daily glass of red wine can reduce heart disease, while drinking several bottles a day is deleterious for health. Similarly, exposure to moderate levels of sunlight is optimal. Hormesis is clearly a general phenomenon, apparently applicable to all environmental agents.