The Assumptions Behind the Assumptions
By Joseph L. Bast, February 19, 2000
Thornton’s Zero Discharge and Clean Production principles, the last of the four assumptions that make up his “new” paradigm, are fundamentally at odds with the conventional scientific notion that there are exposure thresholds below which the body’s ability to repair itself is likely to prevent permanent physical harm. Thornton therefore devotes much space to arguing that such thresholds are arbitrary, apt to be “artifacts of science’s limits,” and so on. (75-80) But he does not explicitly describe the assumptions on which his alternative perspective rests. They are legion.
There is first the Dose-Response Relationship is Linear assumption, which lies at the base of nearly all of his projections of damage to human health. (75, 84, 86) Yet if the relationship between dose and response is not linear -- if it is shaped like a hockey-stick, for example -- then the notion that exposure to very low levels of organochlorides is dangerous is severely attenuated. A healthy scientific debate is taking place over how many dose-response curves are in fact curved rather than linear.
Next is the Single Molecule is Enough assumption, which says the dose-response line is continuous to just one molecule above zero/zero, so exposure to even a single molecule of a toxic agent will cause lasting injury to some small number of people (74). In 400 years, science has yet to come across convincing evidence of a compound whose dose-response curve does not reach the Y axis before (usually well before) coming within a molecule of zero/zero; it is for this reason “the dose makes the poison” is part of conventional science. Thornton asserts that current tests of some organochlorides show us approaching zero/zero, and he assumes that future researchers (especially if freed from cultural and economic influences that blind them to the truth) will eventually establish this to be true of organochlorides as a class. If this is not true, then Zero Discharge and Clean Production become nonoperative.
A third assumption is that A Mouse is a Little Man, which holds that tests on laboratory animals give meaningful data about real world exposure by humans. He cites the International Agency for Research on Cancer, a division of the World Health Organization, to the effect that there is “limited or sufficient evidence of carcinogencity for over 100 organochlorines or groups of organochlorines, comprising over a thousand individual compounds.” (58-9) But he overlooks the point made by Bruce Ames and others that half of all compounds tested are found to be carcinogenic, almost without doubt an artifact of animal testing methods.
Thornton is critical of some aspects of animal testing, particularly of the assumptions that lie behind establishing the no observable affect exposure level (NOAEL), (76-80) but he falls far short of the kinds of criticism of animal testing offered by Elizabeth Whelen, Michael Fumento, and Edith Efron. It is easy to see why. If animals are not reliable stand-ins for humans, then nine-tenths of the research results he reports do not show what he claims they show. Yet faith among scientists in animal testing seems to be dropping faster than Thornton can assemble tests showing a potential threat to human health.
A fourth assumption is that Natural Sequestration Fails. He reports that persistent organochlorides gradually become less bioavailable over time due to sedimentation, but says this isn’t “good enough.” (48) If we grant his Linear Dose-Response and Single Molecule assumptions, then perhaps he is correct. But in the much more likely case that extremely low levels of exposure to organochlorides, like virtually all other compounds studied to date, are not hazardous to humans, then allowing nature to sequester PCBs and other persistent toxins in river sediments, for example, is plainly superior to dredging them up and transferring them to landfills. We might also be heartened by Thornton’s reports that nature transports many errant organochlorides to the polar ice caps where they are sequestered in ice, snow, and the fat of polar bears, pretty much removing them from human contact.
Thornton’s fifth unstated assumption is the Public Interest principle, which (as he formulates it) holds that government officials almost never compromise scientific truth to advance their own self interest, and when by chance they do, their actions tend toward less regulation rather than more. (353) Scientists, in Thornton’s world, may sell themselves out to corporations for status or money, but policymakers still require “overwhelming evidence that a specific chemical has caused harm to public health before action is taken to restrict its production or use.” (114)
But this is a naive theory of how bureaucrats are rewarded and penalized in the real world. In reality they are far more likely to be risk averse than their private sector counterparts, willing to stop any innovation no matter how promising on the most specious of grounds since they stand to profit little by a new chemical’s success, but to lose much if the new chemical is harmful or even controversial. Thornton has some sense of this; he observes, for example, the progressive lowering of legal thresholds for exposure over time, (79) but attributes this trend to the advancing sophistication of scientific tools rather than to bureaucratic incentives.
A sixth unstated assumption is that Complexity is Brittle. Thornton assumes the very complexity of nature makes it vulnerable to the introduction of new compounds that are created by human ingenuity. “Multiple tiny changes can cause runaway or synergistic effects, resulting in a major reorganization or breakdown of the system,” he writes. (340) “Chemicals that are incompatible with ecological and physiological process have not become part of the fabric of life because that fabric was woven by the process of natural selection. . . . An organism that produces chemicals that it cannot degrade or excrete . . . will ultimately perish in the course of natural selection.” (230)
But Nature is Brittle is an assumption, not a fact. The opposite assumption, that complexity is resilient, is just as persuasive and can be backed by as many anecdotes. The tendency for persistent organochlorides to migrate to the poles and into the fat of animals in those frigid parts of the world can be viewed as a marvelous example of resilience: natural sinks emerging to accommodate the new chemical, segregating them from areas (such as the tropics) where they might do the most harm. This is not evidence of impending doom, but of a system able to respond dynamically to a new challenge.
And finally, a seventh assumption, is that Natural is Good, Artificial is Bad. Nowhere in his book does Thornton address the argument put forward by Bruce Ames, the National Academy of Sciences, and other authoritative sources that naturally occurring carcinogens and hormone mimicking compounds exist in our diets at concentrations that are thousands of times greater than the traces of organochlorides he is able to document. If these natural substances are not causing cancer epidemics or widespread sexual dysfunction -- and the evidence is that they are not -- then why should we worry about the possible effects of man-made substances that threaten to have similar effects?
Thornton gives only a desultory defense of the Natural is Good, Artificial is Bad assumption as part of his Nature is Brittle discussions, but his comments show a lack of familiarity with the debate or a deliberate avoidance of the issue. Many of the staples of modern diets date back only a century, so to claim that they are harmless because they are the result of “evolutionary processes” is disingenuous, at best. (230) No, Thornton is blind to the questionable nature of this assumption because he accepts it unquestioningly, and he probably hopes by not mentioning it, the reader will too.
Is Thornton Right About Anything?
Thornton is most believable when he reports that scientists have found traces of PCBs, dioxins, pesticides, and other chlorine-based chemicals in human and animal fat, mothers’ milk, tree bark, fog, bogs, dolphins, whales, cows, snow, ice, and the upper atmosphere. I was amazed -- to the point of reading it out loud to my wife -- by his report that perc, a chemical used by dry cleaners, is so strongly attracted to fat that it has been found in high concentrations in packages of butter sold in nearby grocery stores. (305)
Thornton is also persuasive when he makes the case that human activity is responsible for virtually all dioxin production in the world (209-229), describes the chlor-alkali business and its growing reliance on PVC products to maintain demand for chlorine gas, the production of chlorinated byproducts during the production of commercial products, and the release of dioxin and other compounds during their incineration. His argument that phasing out chlorine would cost less than industry projections is persuasive. Thornton comes across as a more careful student of these issues than any of his predecessors.
If Thornton had limited himself to these areas of discussion and not tried to pass off as valid research that which is junky, or attacked the integrity of scientists in general, or proposed a kind of workers’ paradise where first chlorine and then virtually all other industries eventually get “sunset,” he would undoubtedly have won more converts to his cause. Perhaps it is to his credit that he shares this other agenda with us, rather than attempt to hide it. (As, for example, Theo Colburn tried to do by claiming to have been surprised by her anti-chlorine “discoveries.”) But it will surely alienate scientists, industry leaders, and readers whose political leanings lie anywhere short of the far left end of the spectrum.
Thornton tells us repeatedly that the truth is as simple as 1 + 2 = 3: organochlorides as a class are highly toxic and persistent; conventional science and regulations are not equipped to handle this new threat; the solution is to gradually phase out virtually all uses of chlorine. It sounds simple, but actually he’s presenting us with a + b = c, where the values of each variable depend on the many assumptions discussed earlier, many of them left out of Thornton’s description of his paradigm. Once the entire paradigm is in view, it becomes an unattractive and unpersuasive choice. (Part IV to follow)
Joseph Bast is president of The Heartland Institute and coauthor of Eco-Sanity: A Common-Sense Guide to Environmentalism.