Hormesis Revisited

There are several ways to realize the vast implausibility of — and thus the vast amount of information conveyed by — radiation hormesis. If you are not an experimental scientist, you may not realize how incredibly hard it is to find a treatment that substantially improves something complex. Think how hard it would be to make your laptop work a lot better. Not by redesigning and building a different laptop — but by doing something to the carefully-designed laptop you have now. Has such a thing ever happened in the whole history of engineering? Probably not. Or consider the possibility that shooting a bullet at your laptop (or any other complex machine) will make it work a lot better.  Absurd. Couldn’t possibly happen.

Yet that is exactly what happens in radiation hormesis: Small amounts of radiation improve health. This review article gives a wide range of examples. Experimental:

Bhattarcharjee in 1996 showed that when the mice preirradiated with just adapting doses of 1 cGy/day for 5 days (without a challenge dose), thymic lymphoma was induced in 16% of the animals (Bhattarcharjee 1996). Interestingly, when preirradiated mice were exposed to a 2 Gy challenge dose, thymic lymphoma was induced again in 16% of the animals. However, the challenge dose alone, induced thymic lymphoma in 46% of the mice.


Cancer frequency among [United Kingdom] nuclear power plant workers was lower than the national average (Kendal et al. 1992).

(I’ve never heard anyone complain there wasn’t enough radioactive radon in their basement, but in some cases that’s true.) Thomas Luckey, the discoverer of the effect, wrote a book about it, reflecting the vast number of examples.

What does it mean? Obviously it supports my umami hypothesis. Life evolved in a world of junk and damage; that junk and damage was used to make things work better. Think of a police force. They function best spread over a city, travelling here and there. When there’s a crime, someone will already be close and get there quickly; many crimes will be stopped in progress. A low crime rate is better than a very low crime rate because it gets the police out of the police station and allows them to practice their skills. With too little crime, the police spend most of their time in the police station. When a crime occurs it takes longer to reach the scene (so small problems become big ones) but also, having nothing else to do, they overreact: treat small problems as big ones. That our body’s defense mechanisms are slow to react means infections and cancers become bigger than necessary (and sometimes lethal); that they overreact means we get autoimmune diseases.

Earlier post about hormesis.

4 Replies to “Hormesis Revisited”

  1. You mention radon, which is an area Phil and I’ve worked on. According to Phil, there has been some discussion of the potential protective effects of radon at low levels, but there’s no convincing evidence of this. As you say, it makes some sense, but it also makes sense that even low levels can hurt.

  2. “Cancer frequency among [United Kingdom] nuclear power plant workers was lower than the national average (Kendal et al. 1992).”

    I’m at least as enthusiastic about the idea of hormesis as the next guy but I have to object to that example as evidence for it. I strongly suspect that nuclear power plant workers are exposed to a lot *less* radiation than average workers. Nuclear power plant workers wear radiation tags, spend much of their time in a shielded environment and have people around them at work who are on the lookout for unusual levels of radiation; most workers don’t. Because the danger is so obvious they are overprotected against it, in much the same way that houses in snowy climates are extra-well protected against cold with insulation.

    If you want to look for people likely to be exposed to extra radiation by their jobs, try dentists. Or coal miners. Or people who work outdoors.

  3. Glen, your argument is interesting but it sounds, forgive me, completely armchair. Completely speculative. Especially the idea that the reduced exposure is “a lot” less. I would really like to know of any evidence that supports your claim.

  4. Glen, your argument is interesting but it sounds, forgive me, completely armchair.
    I was wrong. People living near a nuclear power plant are protected to the degree I implied; people working in one aren’t. According to James P Hogan’s essay “Know Nukes” (which I read ages ago), the granite in New York’s Grand Central Station naturally emits more radiation than a nuclear plant is allowed to emit, so people who work there are getting a significant annual dose of radiation, but because we’re not *afraid* of granite, they don’t wear radiation tags. I was extrapolating from that and a few other half-remembered factoids. So let’s get some real numbers in here. A little googling finds these more-precise claims:

    Background radiation (the radiation load from “living on earth” is about 200 mrems. The legal limit on workplace radiation exposure (for nuke workers, x-ray techs, etcetera) is 5000 mrems above background; the NRC claims average industry exposure is about 240 mrems over background; the exposure from being an employee at Grand Central Station is only half that, or 120 mrems. The average exposure from being an airline attendant or pilot is closer – 160 mrems. Medical X-ray technicians average 320 mrems, which is more than the average for nuke workers but not as *much* more than I expected it to be.

    So there are some other professions that are in the same ballpark, but nuclear plant workers do get significant extra exposure relative to “average workers”. I withdraw my objection.

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