Tuesday, 16 June 2015

What's the real risk in a nuclear war?

Most people are very confused about nuclear war because all the information we pick up about it comes from science fiction, fantasy and dystopian culture. Being a child of the nuclear age, I can't help asking myself what's the real risk?

Nuclear bombs are powerful weapons

The data from Hiroshima and Nagasaki tell us that the real risk is immediate and proximate. Nuclear weapons are bombs of immense power. Anyone caught up in the blast radius is at major risk from the blast, the heat, and the electromagnetic (radioactive) pulse. This is all obvious.

If I survived the bombs, could I survive in the resultant nuclear wasteland and fallout?

People frequently write about a nuclear wasteland making life impossible after bombs have dropped. For example:

Three months after an atomic war, the real risk to life is barely measureable. Consider the chart showing how radioactivity decays after a nuclear bomb blast. Notice how sharply the curve falls until it almost flattens out. That's because many of the fission products produced have very short half-lives. They quickly decay into other radionuclides or inactive substances. After 2 hours activity is down to 18% of initial. Thereafter the biggest threat is from iodine-131. Iodine-131 can absorbed by the thyroid and may lead to thyroid cancer. It has a half-life of 8 days, so is thought to pose a real risk for up to 80 days. After 80 days its activity is down to just 0.1% of the initial value. The risk from iodine-131 is mainly to children and teenagers (those still growing). The way to mitigate this threat is to use iodine pills. Longer lived radionuclides such as caesium-137 and strontium-90 have half-lives of 30 years. It won't be until 300 years after the blasts that their activity is down to 0.1%. Yet these longer lived substances pose no big problem for survivors. First, longer half-lives give substances with much lower radioactivity; second, because survivors will be living in areas outside blast radii such as the countryside, suburbs, or small towns; third, because exposure to radioactivity below 100 mSv is not found to pose significant long-term harm to people. There's a radiation threshold we can tolerate. The realization of this threshold is quite recent. Prior to that, nearly all projections made for harm due to post-blast radioactivity and fallout assumed no-threshold. Modeling with no-threshold was regarded as the safe and responsible thing to do. Further, the mathematical model used, called linear no-threshold, LNT, had assumptions to make the maths as easy as possible. It was linear, had no dose threshold, and dose was considered additive. This theory turns science inside out. In place a theory deriving from evidence, LNT is a theory to make modeling as easy as possible. Field evidence doesn't support LNT. Much of the evidence outright contradicts it - showing improved health after low exposure to radiation; what is known as radiation hormesis. In short: when scientists follow the evidence they can't possibly arrive at a LNT model.

What about birth defects?

Don't worry. There's some small danger to pregnant women exposed to the electromagnetic pulse, but no danger to anyone exposed only to fallout. Read: Birth defects among the children of atomic-bomb survivors (1948-1954). Far more harm has been experienced from worrying over this. 200,000 women were persuaded to have abortions after the Chernobyl accident. We're now pretty certain that exposure to the Chernobyl radiation fallout would not have led to even a single birth defect.

Radiation sickness

Again, radiation sickness is only a threat to those exposed to the electromagnetic pulse at the time of an explosion. Such people will be close to the centre of a bomb explosion and be exposed to large amounts of radioactivity (exposure: 1000 mSv or more). It will be a small minority of people. Far more bomb casualties are blast or fire victims. Radiation sickness can lead to death but some subjects do recover. It's caused by massive tissue damage and cell die off.


A larger number of people exposed to a high A-bomb electromagnetic pulse may develop cancer. (exposure: 100 mSv or more).

The Hiroshima and Nagasaki evidence shows the great majority of nuclear bomb victims died due to injuries inflicted by the blast, or fires.

Nuclear Winter?

In the 1970s, some scientists guessed that a large scale nuclear war would lead to fires most everywhere, burning for days on end, sending a plume of dust into the atmosphere. This dust would affect the climate for many months causing global cooling and a nuclear winter. Atomic bomb survivors would be hard pressed to feed themselves after the atomic war. These scenarios are basically models which assume the worse in every case. Other scientists have completely dismissed the nuclear winter scenarios. See: Cresson H. Kearny; Home Office dismissed nuclear winter threat as scaremongering, files show


Provided a bomb didn't drop right on you, and that you weren't in the immediate area of the blast and radiation pulse, you're unlikely to suffer radiation harm. The real threats after an atomic war will be crime, social breakdown, disease and malnutrition. Exactly what we find in the aftermath of conventional war. Even if you're close to an explosion centre, provided you don't die from blast or fire, you're still far more likely to live on, to survive, than you are to die.

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