A review of ACSH's book America's War on "Carcinogens" appeared in the February 8, 2005 Risk Policy Report:
Last month, when the National Toxicology Program (NTP) put 11 more substances on its list of probable carcinogens, it also added 11 exhibits to the argument laid out in America's War on "Carcinogens". Such designations often lead to momentous policy initiatives, such as remediation projects and new pesticide controls, but the methodology and conventional wisdom underpinning them come in for harsh criticism here, warranting nothing less in the authors' eyes than a "paradigm shift" in cancer science and policy.
"High-dose animal studies to characterize risks posed to humans by potential chemical carcinogens are badly flawed," the authors charge. The crack in the current paradigm as portrayed in these pages comes from its overreliance on high-dose animal testing. For instance, a number of NTP's probable carcinogens, including several of the latest additions, have been deemed so solely on the basis of animal research, as is the case too often with cancer evaluations issued by EPA and the International Agency for Research on Cancer, according to the authors. While acknowledging the value of data to be gleaned from animal tests, they charge that policymakers are failing to put such findings in the proper perspective, skirting quantitative risk assessments and epidemiological factors, and not distinguishing between the remotest cancer threats and the most immediate ones. "Most known human carcinogens are also carcinogenic in experimental animals," the authors write; "however, the converse is not true."
In an age convinced it is in the midst of a cancer epidemic, the authors say, this zero tolerance strikes the public, and therefore policymakers, as appropriately vigilant, but a brief survey of cancer history and demographics aims to put cancer's "epidemic" proportions under some scrutiny. The disease emerges as an epidemic only among smokers and today's far larger population of old people. Until the general public gets this message, it will demand policymakers obsess over "speculative causes" at the expense of attacking well-established ones, skewing public-health spending. "Overreliance on animal carcinogenicity testing as a predictor of human health has diverted both public attention and money from important and proven causes of cancer."
After considering the limitations of high-dose rodent bioassays, their emphasis on toxicology as opposed to epidemiology, and the extensive use of such research in forming health and environmental regulations, the authors recount a handful of "cancer scares" over the past 50 years illustrating how badly rodent-reliant science and policy can go awry, ranging from a 1959 cranberry recall to what they describe as a media-driven controversy in 2003 over PCBs in farmed salmon.
All this leads to a series of recommendations designed to correct the paradigm for fighting cancer. The National Cancer Institute, the authors maintain, needs to itself come out with recommendations on updating the cancer classifications in place at NTP and EPA, while Congress should call hearings meant to get the two agencies to reevaluate their approach to risk assessment. EPA should revamp its guidelines for classifying substances into different categories by their carcinogenic potential, to reflect the limitations of high-dose animal testing.
As for the NTP guidelines on designating carcinogens, they too deserve an overhaul that would, among other things, distinguish conclusions based on human data from those relying on animals, the authors say. Without such changes, federal regulators will fail to achieve their proper goal: "to ensure consumer safety without denying the public access to safe, useful products," the authors conclude. "Reform is necessary, if sound decisions are to be made."
