Someone who opposes nuclear power wrote me, “[T]here is no safe level of radioactivity: if I understand it correctly, there is an elevated death rate merely from living near granite, and people regularly die from cancers attributed to cosmic ray damage – and that’s the radioactivity we can’t control.”

It is a common belief that if a lot of something is poisonous, so is a little of something. This is true in spite of what we know about the need for small amounts of salt, fat, and chocolate. Possibly the difference is that if we see a need for a substance, we categorize its dangers differently.

High doses of radioactivity can kill. According to David Bodanky’s Nuclear Energy, intense radiation exposures kill many cells immediately, and lead to death within a short time, at most months. About half of victims of the Hiroshima bombing who receive a dose of at leasst 3 gray (Gy) died (see the end for an explanation of units). Seven out of 23 better-fed Chernobyl victims exposed to between 4 and 6 Gy died. Between 1 and 4 Gy, people usually suffer from radiation sickness, but below 1 Gy, there are usually no clinical symptoms.

People receiving high exposures, even below the 1 Gy level, are more susceptible to cancers. Among the survivors of Hiroshima, by 1990 there had been 421 more deaths from cancer than would have been expected; this number is larger today. No increase in birth defects appeared to have occurred. In the areas around Chernobyl, nine children died from thyroid cancer. In both cases, the doses were high and were delivered in a short period of time.

We are exposed to radioactivity constantly. In the US, radon gas is responsible for the majority of exposure, 2 mSv/yr out of 3.6 mSvy/yr average. In some areas of the US, exposure is much greater, due to the types of rocks, or more cosmic rays due to the height above sea level.

There have been several explorations of the effects of low exposure, this is just one (pdf). The highest measured terrestrial dose, 26,000 mrem/yr, occurs in Ramsar, Iran. Other high annual terrestrial doses occur in areas of Brazil and India (3,500 mrem), China (1,000 mrem), Norway (1,050 mrem), and Italy (438 mrem). The areas in Iran, India, and Brazil are associated with high concentrations of uranium and thorium in the soil. Epidemiological studies of the people in these areas have been made to determine, what, if any, affect these high radiation dose levels have on health. To date, no radiation related health effects have been found. [UNSCEAR 1993; NCRP Report #94] Note that exposures are over a year.

So what might protect us from low doses? From an article by Zbigniew Jaworowski: Each person’s DNA breaks some 70 million times per year due to thermodynamic decay processes and to reactive free radicals, about 5 times/year because of radioactivity. If we did not have a well-developed repair mechanism, our health problems would be considerably larger than they are. (Species with poor repair mechanisms usually live a certain number of breaths, so active flies live a much shorter time than inactive flies. People who get plenty of exercise, on the other hand, have a slightly longer life expectancy.)

On the other hand, low doses may have a protective function (do not do this at home!) See for example The October 17, 2003 Science magazine for two articles on hormesis: Sipping from a Poisoned Chalice (pp 376 – 9) and the embedded A Healthful Dab of Radiation? (page 378). “Low doses of many chemical toxins, from cadmium to pesticides to dioxin, appear to have paradoxical and possibly beneficial effects on organisms—Dioxin is a poster chemical of a bold campaign: to rehabilitate the old saw that poisons or radioactivity at low doses are good for you. The concept (is) known as hormesis.”

“Some studies have found a slightly lower incidence of cancer in people living in places such as western China and Colorado, where natural background radiation levels are three to four times higher than the global average”. In the mid-1980s, … cytogeneticist Sheldon Wolff of the University of California, San Francisco, offered one explanation: When his team “tickled” cells with a low dose of radiation, waited a few hours, then applied a high dose, the cells showed fewer DNA strand breaks than did cells hit only with the high dose. (Read the entire articles for more discussion and caveats.)

So current thinking and evidence points to no harm without a large dose of radioactivity. It also points to tens of thousands of Americans dead from coal power and the transportation fuels in particular. Every year. And then there’s climate change.

If we are to cut carbon emissions 70% worldwide, more than 90% in the US, over 20 tot 25 years, it makes sense to quit worrying about small amounts of radioactivity and worry more about enormous amounts of carbon. If you are a typical American (babies included), you are responsible for 5.5 metric tonnes of carbon emissions per year – that’s just the carbon part of the carbon dioxide molecule. If you are European or Japanese, you’re responsible for almost half this much, and also need to cut back.

*The absorbed dose is the rad or gray: 1 gray is one joule absorbed per kg in the absorber, 1 gray = 100 rad

Dose equivalents are used because some particles drop more of their energy in a short distance, and so do more damage. In particular, alpha particles and neutrons deposit their energy in a shorter distance and do more harm as a result than beta particles with the same amount of energy. It is obtained by multiplying the dose by a quality factor, from Q =1 for x-rays and gamma rays to Q = 20 for alpha particles and fission fragments. One sievert (Sv) is one gray multiplied by a quality factor of 1, while 1 Gy of alpha particles corresponds to 20 Sv. 1 sievert = 100 rem.

m (milli) indicates 1/1000

3 Responses to “Radioactivity”

  1. Dr. Robert C. Amme says:

    Even though the Three Mile Island partial meltdown caused a national panic in 1979, few people seem to understand that the safety systems worked pretty much as planned; no radiation of lasting significance escaped; no one was injured or significantly exposed. Media coverage was sensationalistic. Later, even though Chernobyl was a Soviet Union plant whose function was more than merely generating electricity (it would never have been permitted in the Western world), there were predictions of deaths in the tens-of-thousands range, because improper calculations
    that are today known to be false had been used.
    Low doses of radiation have been shown many times to actually be beneficial–just as low doses of chromium, selenium, and many other “toxic” materials have essential benefits Readers should learn about this “hormesis” effect (just “google” on BELLE, Biological Effects of Low Level Exposures, and follow the several links).
    Nuclear power has a remarkable safety record, even in our submarine fleet. We need nuclear energy badly; it is safe for the environment and must meet our needs for the indefinite future. A hydrogen economy in which the hydrogen is generated principally by high temperature nuclear reactors will at last rid us of our excessive dependence on petroleum.

  2. Jim says:

    Can you include in your assessment the effects of radioactive fallout on the people of Rongelap and other atolls in the Marshall Islands? There is evidence of a high rate of birth defects, including very severe defects – ‘jellyfish’ babies. There was a long-term project monitoring health effects as well as conducting additional experiments (without informed consent, of course) on the survivors by the Brookhaven labs, but much information hasn’t been released. Holly Barker’s ‘Bravo for the Marshallese’ is the most accessible account.

  3. Michael Gembol says:

    Dear Musing:

    A former nuclear power plant engineer and operator, the effects of a meltdown and release were drilled into me. I was taught to do the calculations. A large nuclear plant meltdown could kill millions downwind and leave entire state-size areas uninhabitable. But a meltdown would release only a small fraction of the total radioactive material. By contrast, a terrorist nuclear bomb, (a “nuc-on-nuc” scenario) would vaporize an entire power station, the 2 or 3 operating plants plus all the spent fuel in storage, and put the entire mass of radioactive material into the stratosphere for the jet streams to carry around the world. The resulting plume would have somewhere around 10,000 times the radioactivity released in a hydrogen bomb. Depending on weather and wind patterns, it would wrap around the world again and again, creating a 100% lethal area over entire continents. I am not capable of modeling the fallout distribution of various isotopes, or the reconcentration of substances in the food chain, but there’s enough radioactive material to eradicate the human race if spread over the globe evenly.

    We also live under the threat someone will target a nuclear reactor plant as a military tactic and release a fallout plume 10,000 times too large, to everyone’s surprise. I can’t hear of “bunker busting nucs” and options to bomb Iran’s nuclear plants without a shudder. Where do they think the fallout would end up? Restrained by Iran’s downwind border somehow? It would be distributed at lethal levels over the entire northern hemisphere, at least. Billions might die. The death toll could reach 6.6 billion, not that anyone would be left to count. Is there any political or economic or religious interest that justifies this? Would anyone take the risk in pursuit of profit or votes? Sadly, there seem to be some willing to take us to the brink of this ghastly abyss without our common consent, exploiting our common ignorance of the risk.

    There’s no insuring such losses. We can’t insure even a simple meltdown. Depopulating continents and hemispheres forever is just not assessable. It exceeds the human capacity to imagine. It is infinity on a scale of 1 to 10. The articles in today’s Musing Environment deal with a scale of 1 to 10. Infinity is on the table. Nuclear power plants are not the answer. They cannot be made safe, they cannot be defended. A “100% safe” HTGCR is just as lethal in a nuc-on-nuc scenario as a 70’s BWR. Do not build more, not even in India, not even if the industry presents itself as the solution to greenhouse warming. If the issue comes into public discussion, please, please, please put ALL the facts before the public.

    Please post this. And send a copy to Dr. Robert C. Amme.

    Michael Gembol