I am writing about concerns I have regarding the letter New software for modelling impacts of regional nuclear war in the New Zealand Medical Journal of 3 July 2009 (Vol 122 No 1298). I am a member of the National Consultative Committee on Disarmament and when I raised this issue at a recent meeting the Chairman, Dr Rod Alley, suggested that I should write to you.

I certainly agree with, and appreciate, the points which are made in the letter regarding the effects of the dust in the atmosphere which would be caused by the explosion of nuclear bombs, and the severe damage which would be caused, and you may well say that describing these effects ought to be sufficient to awaken people to the dangers of nuclear conflict, even to countries which have not taken part in it.

Nevertheless it seems to me that a nuclear conflict would have even more immediate results which ought to be considered. You speak of the atmospheric dust as if it were like the dust from, for example, a volcanic eruption. But the dust from the explosion of nuclear bombs would contain radioactive dust.

It used to be thought that the radioactivity from nuclear explosions was confined to the area of the explosion. But researchers into the effects of the explosion of DU weapons, such as Dr Chris Bushby in a book produced by the United Nations Institute for Disarmament Research—the Disarmament Forum book—have shown that dust from those explosions travels long distances in the air and is inhaled by humans or animals, or else eventually settles in the soil or groundwater, so that it is ingested by people or animals who drink the water or eat plants which have absorbed it. It has been shown by medical tests that it remains in the body tissues for a long time.

If this is so of the explosions of depleted uranium weapons, how much more would it be true of uranium bombs made of full-strength enriched uranium, much more powerful and more numerous. Dr Ian Fairlie in an article The Health Hazards of Depleted Uranium published in the Disarmament Forum magazine has discussed the health hazards of uranium. He states:

It seems to me that this information about the immediate and great dangers posed to those who inhale or ingest the radioactive dust produced by the explosion of nuclear bombs is even more important that what is in your article, and should have been included in it.

In response to the above letter (commenting on our previous letter1) we note that our aim was to address an under-recognised impact of regional nuclear war: that of fire-induced atmospheric dust spreading globally. In such a brief letter it was not possible to adequately survey all the adverse impacts of nuclear war which span direct local impacts2 as well as global impacts relating to ozone destruction, radiation dispersal and social and economic collapse of countries affected by trade disruptions.3–7

Nevertheless, we agree that a nuclear war would likely result in substantial stratospheric injection of radionuclides that spread globally. This problem has been quantified previously around a large US-Soviet nuclear war for New Zealand8 and for the Southern Hemisphere as a whole.3

For regional nuclear war between China and India it has also been estimated that radiation could be expected to cause 230 fatal cancers per million people in the Northern Hemisphere and 0.2 per million in the Southern Hemisphere (or more precisely, at latitude 20 to 40 degrees North in the Northern Hemisphere and at latitude 30 to 50 degrees South in the Southern Hemisphere).9 But these calculations involve many uncertainties—e.g., ground bursts versus airbursts of the nuclear weapons, the explosive size of the weapons (kilotonnes/megatonnes), the size of fires in attacked cities, whether or not nuclear power plants are attacked, and also the estimated hazard of low-level radiation for cancer causation.

The complexity of assessing the impact of radioactive fallout on the New Zealand population from nuclear war is increased when considering how weather patterns (particularly rainfall) determine radionuclide deposition rates. Some individuals and industries may also act in a post-war setting to reduce radionuclide intake via the food pathway. Such measures include using pre-war powdered milk instead of fresh milk (and other pre-war stored food), increased washing of fruit and vegetables, and avoiding certain fresh foods produced in high rainfall areas etc.

Even so, given the estimate above for radiation-induced cancers from a China-India nuclear war, it is unlikely that radiation would be a major health problem for New Zealand compared to the other impacts of a regional nuclear war. That is why we consider that nuclear disarmament activities are far more likely to be stimulated by concerns of nuclear winter-type impacts from fire-related dust in the stratosphere than radiation concerns—especially if these climate impacts could cause a billion deaths from starvation as previously estimated.7

As we argued before,1 the New Zealand Government and its citizens need to do much more to prevent nuclear war for numerous reasons and such activities would build on the strong track record that this country has already established.10 Even so, such efforts also need to be balanced with the urgent need to address other global problems such as climate change.