Will radiation hormesis protect us from exploding nuclear reactors?

That reputable scientist, Ann Coulter, recently wrote a genuinely irresponsible and dishonest column on radiation hormesis. She claims we shouldn't worry about the damaged Japanese reactors because they'll make the locals healthier!

With the terrible earthquake and resulting tsunami that have devastated Japan, the only good news is that anyone exposed to excess radiation from the nuclear power plants is now probably much less likely to get cancer.

This only seems counterintuitive because of media hysteria for the past 20 years trying to convince Americans that radiation at any dose is bad. There is, however, burgeoning evidence that excess radiation operates as a sort of cancer vaccine.

As The New York Times science section reported in 2001, an increasing number of scientists believe that at some level -- much higher than the minimums set by the U.S. government -- radiation is good for you.

But wait! If that isn't enough stupid for you, she went on the O'Reilly show to argue about it. Yes! Coulter and O'Reilly, arguing over science. America really has become an idiocracy.

I only know about hormesis from my dabbling in teratology; a pharmacologist or toxicologist would be a far better source. But I know enough about hormesis to tell you that she's wrong. She has taken a tiny grain of truth and mangled it to make an entirely fallacious argument.

Radiation is always harmful — it breaks DNA, for instance, and can produce free radicals that damage cells. You want to minimize exposure as much as possible, all right? However, your cells also have repair and protective mechanisms that they can switch on or up-regulate and produce a positive effect. So: radiation is bad for you, cellular defense mechanisms are good for you.

Hormesis refers to a biphasic dose response curve. That is, when exposed to a toxic agent at very low doses, you may observe an initial reduction in deleterious effects; as the dose is increased, you begin to see a dose-dependent increase in the effects. The most likely mechanism is an upregulation of cellular defenses that overcompensates for the damage the agent is doing. This is real (I told you there's a grain of truth to what she wrote), and it's been observed in multiple situations. I can even give an example from my own work.

Alcohol is a teratogenic substance — it causes severe deformities in zebrafish embryos at high doses and prolonged exposure, on the order of several percent for several hours. I've done concentration series, where we give sets of embryos exposures at increasing concentrations, and we get a nice linear curve out of it: more alcohol leads to increasing frequency and severity of midline and branchial arch defects. With one exception: at low concentrations of about 0.5% alcohol, the treated embryos actually have reduced mortality rates relative to the controls, and no developmental anomalies.

If Ann Coulter got her hands on that work, she'd probably be arguing that pregnant women ought to run out and party all night.

We think there is probably a combination of factors going on. One is that alcohol is actually a fuel, so what they're getting is a little extra dose of energy; it's also deleterious to pathogens, so we're probably killing off bacteria that might otherwise harm the embryos, and we're killing those faster than we are killing healthy embryonic cells. It's the same principle behind medieval beer and wine drinking — it was healthier than the water because the alcohol killed the germs.

However, the key thing to note about hormetic effects is that they only apply at low dosages. Low dosages tend to be where the damaging effects are weakest, anyway, and where the data are also the poorest. The US government recommendations for radiation exposure are based on a linear no threshold model in which there is no hormesis to reduced effects at low concentrations for a couple of reasons. One is methodological. The data we can get from high exposures to toxic agents tends to be much more robust and consistent, and we do see simple relationships like a ten-fold increase in dose produces a ten-fold increase in effect, whereas at low doses, where the effects are much weaker, variability adds so much noise to the measurements that it may be difficult to get a repeatable and consistent relationship. So the strategy is to determine the relationships at high doses and extrapolate backwards.

Then, of course, the major reason recommendations are made on the simple linear model is that it is the most conservative model. The data are weaker at the low end; there is more variability from individual to individual; the safest bet is always to recommend lower exposures than are known to be harmful.

In the low dosage regime, these responses get complicated at the same time the data gets harder to collect. This is why it's a bad idea to base public policy on the weakest information. I'll quote a chunk from a review by Calabrese (2008) that describes why you have to be careful in interpreting these data.

In 2002, Calabrese and Baldwin published a paper entitled "Defining hormesis" in which they argued that hormesis is a dose-response relationship with specific quantitative and temporal characteristics. It was further argued that the concept of benefit or harm should be decoupled from that definition. To fail to do so has the potential of politicizing the scientific evaluation of the dose-response relationship, especially in the area of risk assessment. Calabrese and Baldwin also recognized that benefit or harm had the distinct potential to be seen from specific points of view. For example, in a highly heterogeneous population with considerable inter-individual variation, a beneficial dose for one subgroup may be a harmful dose for another subgroup. In addition, it is now known that low doses of antiviral, antibacterial, and antitumor drugs can enhance the growth of these potentially harmful agents (i.e., viruses), cells, and organisms while possibly harming the human patient receiving the drug. In such cases, a low concentration of these agents may be hormetic for the disease-causing organisms but harmful to people. In many assessments of immune responses, it was determined that approximately 80% of the reported hormetic responses that were assessed with respect to clinical implications were thought to be beneficial to humans. This suggested, however, that approximately 20% of the hormetic-like low-dose stimulatory responses may be potentially adverse. Most antianxiety drugs at low doses display hormetic dose-response relationships, thereby showing beneficial responses to animal models and human subjects. Some antianxiety drugs enhance anxiety in the low-dose stimulatory zone while decreasing anxiety at higher inhibitory doses. In these two cases, the hormetic stimulation is either decreasing or increasing anxiety, depending on the agent and the animal model]. Thus, the concepts of beneficial or harmful are important to apply to dose-response relationships and need to be seen within a broad biological, clinical, and societal context. The dose-response relationship itself, however, should be seen in a manner that is distinct from these necessary and yet subsequent applications.

I know, the Cabrese quote may have been a little dense for most. Let me give you another real world example with which I'm familiar, and you probably are, too.

Here in Minnesota in the winter we get very snowy, icy conditions. If I'm driving down the road and I sense a slippery patch, what I will immediately do is become more alert, slow down, and drive more carefully — I will effectively reduce my risk of an accident on that road because I detected ice. This does not in any way imply that ice reduces traffic accidents. Again, with the way Ann Coulter's mind works, she'd argue that what we ought to do to encourage more responsible driving is to send trucks out before a storm to hose the roads down with water instead of salt.

Ann Coulter is blithely ignoring competent scientists' informed recommendations to promote a dangerous complacency in the face of a radiation hazard. She's using a childish, lazy interpretation of a complex phenomenon to tell people lies.

Calabrese EJ (2008) Hormesis: Why it is important to toxicology and toxicologists. Environmental Toxicology and Chemistry 27(7):1451-1474.


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