Invisible harm from ionizing radiation

Besides the terrible effects of the burst of light that causes eye damage, the heat that sets everything flammable on fire, the electromagnetic pulse that knocks out all electronic devices, and the blast that produces winds with ten times the force of a hurricane, demolishing everything, the detonation of nuclear weapons also leads to the emission of large amounts of ionizing radiation, which has serious deleterious effects on humans and many other species. Ionizing radiation is, in fact, a lurking danger as we cannot see it, we cannot smell it, we cannot hear it, and we cannot feel it immediately. But we certainly get harmed from it.

To reduce exposure to ionizing radiation and the risk of deleterious effects, we doctors usually warn our patients against having frequent examinations or procedures that involve x-rays. That is because x-rays are ionizing radiation that can harm your body in the same ways as radiation emitted by nuclear detonations. The main difference is that, for medical purposes, the radiation is applied in a controlled way.

The international standard unit for the dose of ionizing radiation is the Sievert. National guidelines in many countries warn against people having a cumulative dose of ionizing radiation exceeding 0.001 Sievert/year.  The dose from a full body CT scan is 0.01 – 0.03 Sievert.

The ionizing radiation to which everybody in the vicinity of a nuclear detonation is exposed is so high and immediate that measuring in Sievert does not have much meaning. Such exposures are measured in Gray, where five Gray is reckoned to be lethal to 50% of those exposed (LD50). Even though these types of exposures are not directly comparable, for the common types of ionizing radiation, 1 Gray equals approximately 1.3 Sievert.

The intensity of the radiation at the epicenter of the atomic bombing of Nagasaki was estimated to be 320 Gray; one kilometer away it was 7.83 Gray; two kilometers away it was 0.13 Gray. The first two exposures are lethal; the third is about 130 times above the recommended yearly dose for humans.  In an attempt to transform the radiation from a nuclear explosion into a standardized dose estimate, the highest reading of ionizing radiation from the fallout from the Trinity bomb, 32 km away from the detonation, and 3 hours later, was 0.190 Sievert/hour which equals 1.700 Sievert/year. There is evidence that a single dose of about five Sievert may be lethal. Cancer risk in general is reckoned to increase by approximately 5.5% for every Sievert/year.

Ionizing radiation and, in particular, gamma radiation, can penetrate tissue and cause harm throughout the body. Cells that have rapid life cycles are the most susceptible to acute damage. If the dose is high enough, the irradiated cells are simply killed by the radiation. That knowledge is used in all kinds of radiotherapy. The most susceptible cells are those of the central nervous system, blood cells, gamete cells, and barrier cells in the gastrointestinal tract. Therefore, symptoms of acute radiation illness are drowsiness and convulsions, anemia and bleeding, and loss of body fluid by bleeding and through the gut. Patients are seen more or less unconscious with skin hemorrhages and bleeding out of every opening of the body. No treatment is available apart for attempts for symptomatic relieve.

Long term effects of too much ionizing radiation include congenital malformations from genetic damage to gamete cells, and an increased risk of different types of cancer as seen in the cohorts of survivors from the  atomic bombings of Hiroshima and Nagasaki during the past 70 years.

Detonation of a nuclear bomb generates both direct ionizing radiation from the explosion and also huge amounts of radioactive contamination that can spread with the wind into the atmosphere and precipitate as “fallout” onto land or water. The same can happen as a consequence of nuclear reactor disasters, such as Chernobyl and Fukushima. Such radioactive fallout is immediately deleterious to both humans and animals and can make large areas of land uninhabitable, unpastoral, and uncultivable for decades.

Ionizing radiation is normally present in nature from many sources in the Earth’s crust. Humans and animals have evolved to endure small amounts of ionizing radiation, with an assumed (but nevertheless controversial) “safe” dose of less than 0.001 Sievert/year. That is a fine and tender balance that should not be disturbed by the emission of unnecessary and dangerous  ionizing radiation anywhere into the environment, whether by nuclear weapons or other human activities.