The International Agency for Research on Cancer is renowned for producing assessments of carcinogens. But it appears that some of the agency’s evaluations may overstate the risks, for reasons that tell us a great deal about the science and politics of risk assessment.
It is a paradox that, in spite of dramatic increases in life expectancy and improvements in health in the developed world over recent decades, as a society we are obsessively preoccupied with the specter of hazards lurking in our environment and consumer products.
Many factors have contributed to this ever-increasing climate of fear, including the success of the environmental movement; a deep-seated distrust of industry; the public’s insatiable appetite for stories related to health, which the media duly cater to; and – not least – the striking expansion of the fields of epidemiology and environmental health sciences and their burgeoning literature. ...
... One has to ask what “possibly carcinogenic” means, if extensive evidence in humans and animals points to no threat. A major problem with the IARC process is that it makes it almost impossible to assign an agent to category 4 – probably not carcinogenic. Of the roughly one thousand agents evaluated by the agency exactly one is in this category.
A second problem with the IARC process — one that reinforces the classification problem — is that some of the working groups convened to assess a particular agent have included scientists who have carried out studies on the agent under evaluation. It is fanciful to think that scientists who have a vital stake in a particular question can evaluate the evidence, including their own studies, dispassionately.
Finally, IARC reaches its assessments by consensus. But this can mean that those who are more forceful and persuasive may influence the group decision-making process. In addition, consensus implies a philosophic stance which has nothing to do with science.
All three of these flaws came together in IARC’s assessment of cell phones: undue emphasis on a small number of positive epidemiologic studies from a single group, when the much larger body of studies indicated no elevated risk; the improper influence of an activist researcher (the lead author of the anomalous positive studies) on the deliberations of the working group; and, finally, a tilt toward the “precautionary principle.”
The precautionary principle states that, if there is uncertainty regarding the effects of exposure to an agent, the burden of proof that exposure does not cause harm falls on those who utilize the agent. While this formulation may sound reasonable, in actuality it has nothing to contribute to the assessment of risks. First, there are always uncertainties, and it is not possible to prove the absence of risk. Furthermore, in practice invocation of the precautionary principle focuses attention solely on the possibility of harm, often ignoring information about the dose to which people are exposed, avoiding consideration of benefits of the agent in question and whether safer substitutes are available, and giving greater weight to studies that appear to indicate a hazard, even when these studies may be of poorer quality.
For all its self-justifying claims, the precautionary principle seeks to deny a central fact – there is no way to avoid risk in life – all we can do is to try to use available knowledge to distinguish between large, well-established risks; those that are probable; and those that available evidence suggests are trivial or non-existent. ...
Geoffrey C. Kabat is a cancer epidemiologist at the Albert Einstein College of Medicine and the author of Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology.