There are many examples of misuse of science in environmentalism, so this title could obviously introduce quite a long essay. However, as I have already dealt with many issues, today I want to address just one, the concept of hormesis, or the foolishness of assuming a linear dose-response curve.

This is an error you see in many cancer studies, or studies of "diffuse environmental toxins". A scientist will study a given chemical by feeding truly horrendous quantities to lab animals, or inserting large quantities under their skins. When they develop cancer, he takes the time it took, divides it by the dose and decides that at a microscopic dose it would take 10 years to get cancer.

All of which is nonsense. The human body simply does not work that way. And there is sufficient evidence to prove it.

For example, take water. If you drink a glass, it is absolutely harmless, which, using the linear assumption of most studies, means there is no harm no matter how much you drink. However, drink 10 gallons at once (if you can), and either your organs will rupture or an electrolyte imbalance will do you in. By that logic, water is a toxin, and you will eventually die from that single glass, just slowly.

What we are seeing is a principle described long ago, hormesis. Most often this is phrase :Nothing is a food, and nothing is a poison, but the dose makes it so." And that is true of "unnatural" chemicals as much as it is of the many substances with which we are familiar.

Let us take another example. Vitamin C. We are all familiar with this vitamin, mainly because of the false claims put forward by Linus Pauling. However, in recent years it has again received attention thanks to being dubbed an antioxidant, that holy grail of the anti-aging crowd. Except that it isn't. Studies show that vitamin C is a powerful antioxidant, but only within a range of doses, at extremely small and extremely large doses, some studies show that it actually is an oxidizer, having exactly the opposite effect. This flies in the face of the simple minded linear dose-response curve on which much of environmental science is based.

A similar study was done with lab rats during the Manhattan Project, testing the risks to uranium miners. Despite the simplistic assumptions that small doses of radiation would simply have smaller harmful effects, it turned out that rats exposed to small doses of radiation actually were longer lived than the control rats. Some have used this to argue for the principle of "sufficient challenge", that small doses of toxins  kill off weaker cells, or cause the body to strengthen itself in other ways, resulting in improvements, rather than damage. Others argued that the small doses of radiation had more chance of killing off harmful parasites and germs than damaging cells, leading to improved health. Whatever the reason, it still contradicts the simple dose-response curve upon which our public policy is based.

And there is even more evidence. For example, some chemical have a rigid linear dose response curve, others have a variable one, and still others behave in even more unusual ways. For example, tylenol, while having a linear dose response curve, also has a lifetime limit, beyond which harm is likely regardless of dose. Or opiates, which, while they have a linear dose response for any individual, also induce tolerance, so an individual's response varies over time, as they become capable of tolerating larger and larger doses. All of which fits poorly with the models used to create public policy (and lucrative lawsuits).

Now, let me break here and state that scientists themselves are aware oft his, for the most part, and most real science does not start with the assumption that all chemicals have a linear dose-response. But there are those who do*. And often those who promote such simple-minded approaches are the scientists who will be cited by lawyers and legislators, leading to the worst science driving the bulk of public policy.

Here it is traditional in such posts to suggest solutions to the problem described, but, unfortunately, I don't have easy solutions. Ideally, the government would get out of the field entirely, and the civil courts would settle things. But with the bad science permeating civil suits, and the absurd suits that class action and very lenient laws concerning the statute of limitations have created an environment conducive to really bizarre lawsuits, we need a lot more reform before that is possible as well. Which means any proposed solution would run page after page, all filled with "if X then we can Y", which makes for very boring reading.

So, for now, let me just suggest that readers not immediately assume that something is dangerous at any dose just because a vat of it causes some harm. And, more importantly, not buy into any laws or lawsuits premised upon such assumptions. It is a small victory, but if everyone were to do that, we might avoid some of the worst environmental abuses.

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* For an example of this, read some essays on mechanisms of carcinogenesis, then read lawsuits.You will not only see that lawyers often propose mechanisms the science argues are unlikely, but they even cling to theories that have been wholly discredited. (Eg. Look up traumatic cancer, and note people were still winning traumatic cancer suits decades after science had declared it nonsense.) Then again, our government still bases policy on absurd science as well. For example, it appears likely saccharine is dangerous, but mainly to female rats, thanks to suspended proteins in their urine. Humans are unlikely to have the same problems, yet the FDA still requires warning of a threat only likely to harm rats.

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POSTSCRIPT

I was going to cite Rational Readings on Environmental Concerns (ed. Jay Lehr) again as a source for Gold and Ames, but I found an even better source. It appears Lois Swirsky Gold is still working in the field and publishing. So, I can direct readers to the Carcinogenic Potency Project. I know some will dismiss the group as biased and "non-scientific", just as many dismiss those opposing AGW. However, Ames definitely knows something about cancer, and Gold is well qualified as well. This is not another Linus Pauling giving advice outside of his field of expertise, these are experts on cancer, carcinogenesis and testing, and they argue our testing methodologies are geared toward systematically overestimating the risks of cancer. There is even an online book available explaining their position. Even if you don't end up agreeing with me, it is still a good read.
 

POSTSCRIPT II

My earlier environmental posts can be found in the postscript to "Interesting Evidence".