Alarmism is harmful at any dose. Just as political mudslinging can unfairly sully reputations, sensational news about health dangers can rattle public confidence -- whether or not the sensational report turns out to be true. "Something about modern living has driven a steady rise of certain maladies," reports a front-page article from the July 25th Wall Street Journal, which goes on to say that the culprit may be "the prevalence of certain industrial chemicals at extremely low levels [in the environment]." An issue of profound importance is raised by this startling declaration: exactly how dangerous are the industrial chemicals that are increasingly prevalent in our environment, and are they really causing an epidemic of cancers and childhood brain disorders?
The science of low-dose exposure is still in its infancy. New and more precise methods have made certain industrial chemicals detectable at levels as minuscule as parts per quadrillion (imagine one postage stamp on a letter the size of California and Oregon put together), but scientists are a long way from a consensus about what impact, if any, minute quantities of certain chemicals have on human health. Without so much as one reference to a specific peer-reviewed paper, Peter Waldman, author of the WSJ piece (the first in a series entitled "Toxic Traces"), implies that detection of these chemicals is somehow related to an apparent increase in everything from prostate cancer to autism.
In fact, two other aspects of modern living, while perhaps not as front-page-worthy, are more likely explanations. First, we are living longer due to medical advancements. Since cancer is primarily a disease of old age, it is not surprising that the prevalence of some cancers is increasing concurrently with life expectancy, giving the illusion of a "cancer epidemic." Second, improved medical technology and broadened diagnostic criteria are making conditions like autism more readily detectable, leading to the increased diagnosis and reporting of many diseases.
Scientific research using rodents and other animals as proxies has long been a mainstay of toxicology, given that ethical issues preclude conducting human experiments. As the article correctly points out, some studies link high-dose exposure to certain common industrial chemicals with cancer in rats. However, similar studies link mushrooms, sweet potatoes, and other natural foods with rodent cancer as well.
But Waldman is making mountains out of rat-hills. It is prudent to remember that a rat is not a little man and that many of these studies cannot even be replicated in other rodent species, much less extrapolated to humans. In what is perhaps the furthest thing from a sound argument (but an all-too-common tactic these days), Waldman repeatedly implies that many of those who object to increased regulation at the drop of a rat do so because they are funded or employed by industry. Such charges are what happens when ideology becomes more important than sound science, when suddenly academia and industry-funded science are portrayed as competing forces with opposite goals. In reality, some scientists simply don't see unreplicated, single-species studies as sound evidence of a threat to human health.
In vitro research on human cells is another indispensable tool in toxicological research. But to assume, as Waldman seems to, that human cells always respond within the complex system of the human body in the same way that they do in the isolation of a Petri dish is a leap of logic that some scientists are simply not prepared to make. As the author points out, academic studies typically seek to determine whether a chemical has an intrinsic capacity to do harm, whereas scientists affiliated with industry are often more concerned with measuring actual dangers to human health. Those who dispute the validity of some of the tests to which Waldman refers are not doing so because they are in the pocket of big business but rather because they view such proxies as a necessary-but-not-sufficient way of determining threats to human health. Rodent studies and in vitro cell studies may be good places to start when investigating potential harm from chemicals. However, more evidence is necessary before good regulatory decisions can be made and certainly necessary before making claims that scare the daylights out of consumers.
Perhaps the most intriguing part of the article is Waldman's discussion of possible evidence for a reversal of the traditional dose-response axiom "the dose makes the poison." Alluding to rodent studies that are still controversial in the scientific community, Waldman asserts that some chemicals such as bisphenol-A (BPA) may actually be more harmful at low doses than at high doses. However, the metabolism of BPA is more rapid and complete in humans than in rodents (1), and the decisions by regulatory agencies both in the U.S. and Europe not to increase regulation of BPA reinforce the conclusion that there is little evidence of low-dose effects. Waldman would have us believe, however, that such agencies are under the barrel of a big-business gun. In reality, understanding of the dangers of exposure to low doses of such chemicals is still developing. While it merits further study, there is simply not yet enough data on which to make assertions such as Waldman's, which if acted upon would consign many useful and safe consumer products to the dustbin.
The article appeals to the emotions and fears of consumers who are ill-equipped to understand the underlying scientific controversy, all the more so because there are no specific citations to support the author's frightening claims; a consumer who is interested in pursuing further information is left without the tools to do so. Of course, all of the preliminary findings mentioned in the article should be further investigated. But claims about danger from trace levels of chemicals have no place in newspapers unless they are dealt with responsibly and placed in better context.
1Kamrin, Michael A. Bisphenol A: A Scientific Evaluation. Available (to members) on MedScape Today: http://www.medscape.com/viewarticle/484739?src=search.
Mara Burney is a research associate with the American Council on Science and Health (ACSH.org, HealthFactsAndFears.com).
See also: ACSH's new report on Biomonitoring: Measuring Levels of Chemicals in People -- and What the Results Mean.