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Misconceptions about the Causes of Cancer Vancouver, British Columbia, The Fraser Institute, 2002 Misconceptions about the Causes of Cancer argues that the debate about unproven cancer causes diverts attention and resources away from establishing health policies and interventions to address the well-established avoidable causes of cancer, including smoking and dietary factors. Such argument has been widely popularized in the field of risk regulation in the US by Aaron Wildavsky1 from Berkeley and John Graham from Harvard University.2 These ideas have made their way into US jurisprudence in looking at the costs of environmental, health and safety regulation. In many respects, the complex arguments turn on three points: a) what is the acceptable public price of one life saved by a regulatory intervention; b) to what extent are high-cost/low-yield regulations impeding other more effective preventive health services; and c) if we let everyone get wealthy, we will be safer without regulatory intervention, and high-cost/low-yield regulatory intervention is impeding our wealth and potentially our health. In the extreme, this position reduces to the idea that the cost of regulation should be put back into the hands of the taxpayer and the resulting gain in wealth would result in better overall health. This philosophy resonates with the ideologically libertarian Fraser Institute since it accords with the notion of minimal government interference in regulatory matters. Three of the authors, Swirsky Gold, Slone and Manley, are affiliated with the Carcinogenic Potency Project at the University of California, Berkeley. The fourth author, Ames, is well known in toxicology and as a former Berkeley professor and is currently Senior Scientist at Children's Hospital Oakland Research Institute. The authors identify nine misconceptions about what causes cancer, and discuss each of these in the context of current research. In Chapter 1, entitled, "Misconception 1 - Cancer rates are soaring in the United States and Canada", the authors draw on data from the National Cancer Institute of Canada that show a decline in overall cancer mortality rates in Canada; however, this decline, as they point out, is primarily due to selected cancers (stomach, cervix and colorectal). They cite a similar decline in the United States. Misconceptions about the Causes of Cancer does not report cancer incidence; it states changes in incidence rates over time which are complicated by more recent screening programs, diagnostic innovations and changes in lifestyle trends. Nevertheless, it seems irresponsible of the authors to dismiss the fact that increases in the population and population aging will contribute to dramatic increases in cancer incidence, thereby placing greater demands on the cancer delivery system.3 Eight more chapters are dedicated to misconceptions about synthetic chemicals, pesticides, assessment of carcinogenic hazards, and regulation of environmental risks. These chapters advance the central thesis that environmental risk factors are far down the list of known carcinogens. For example, the authors point out that most of the studies of potential environmental carcinogens are based on animal models that involve substantially higher dose levels (the "bioassay design") than humans would incur in their lifetimes. They also argue that it is not possible to generalize the results to human beings due to inter-species differences. There is also a misconception, the authors state, that synthetic chemicals pose greater cancer risk than natural chemicals. Their research shows, however, that "... a high percentage of both natural and synthetic chemicals are rodent carcinogens at the MTD [maximum tolerated dose] and that tumor incidence data from rodent bioassays are not adequate to assess low-dose risk". Chapter 7 presents this analysis and summary ranking of several potential human cancer hazards (synthetic and natural), based on the authors' previously published work. This index, the "human exposure/rodent potency index" (HERP), was used to rank the potential cancer risks. Compared to many common exposures, the HERP index shows that synthetic pesticides rank comparatively low in potential carcinogenic hazard. Furthermore, the authors state that solid scientific evidence does not exist to support a relationship between pesticides and other synthetic chemicals and the disruption of hormone levels that could lead to the development of certain cancers (e.g., breast cancer). Finally, in Chapter 9, the authors maintain that existing and proposed regulations to deal with these potential risks are very expensive, and divert scarce funds away from cancer prevention initiatives and policies supported by science. Once again, this tradeoff position of the dubious costs of regulation represent a US public policy tradition which is not without its detractors within the US public policy debate, and a tradition which is not necessarily embraced by other advanced nations. This regulatory debate on what is considered to be a legitimate health or safety regulation limiting trade and what is an unfair trade practice is being fought daily in the corridors of the World Trade Organization.4 Misconceptions about the Causes of Cancer adheres to its main argument that existing science does not support claims made about the carcinogenic effects of synthetic chemicals. This little book is not, however, without its limitations. No clear or systematic methodology is presented for identifying and selecting studies from the published literature to support the line of argument. No review criteria are provided. The authors appear to rely primarily on their own research when citing references to support their conclusions. The text is primarily narrative; levels of evidence are not used to assess the quality of the science to support or refute claims made about potential cancer risks. Finally, the authors skip the major area of occupational exposures and human cancers. In addition, there is no discussion of the relationship between the environment and cancers in young adults. For example, there are good studies linking pesticide use among farmers and wood dust among forestry workers to non-Hodgkin's lymphoma.5 Both exposures require regulatory interventions to prevent high concentrations of environmental carcinogens in small numbers of highly exposed populations. Likewise, while it is accurate to say that the overall pattern of cancer mortality is in decline in North America, the growth in some cancers in young adults, such as non-Hodgkin's lymphoma, a cancer which has grown by 3.9% annual increase in males, and 5% annual increase in females in Canada from 1987 to 1996, remain unexplained. While infectious factors may be important, environmental factors and occupational exposures remain important suspects in the rise of this cancer. The absence of environmental evidence does not mean that evidence does not exist. It doesn't mean it does exist either - simply that we have no evidence yet. Despite the controversy attending the science surrounding the use of ornamental pesticides, the Supreme Court of Canada, invoking the precautionary principle, has indicated that municipalities have the right to introduce bans on the use of ornamental pesticide.6 Apparently our own Supreme Court does not subscribe to the Wildavsky-Graham position. Policymakers should read Misconceptions about the Causes of Cancer. The authors have provided some evidentiary basis for their argument, even if it is a selective reading of the literature in the tradition of US environmental regulation. We are convinced that special consideration should be given to identifying an appropriate balance between current regulations and resources attached to those cancer risks for which there is established scientific support (those where the burden suggests a strong focus on smoking, diet, physical inactivity, sun exposure). Ongoing research into potential environmental and occupational risks must be supported, however, and each national jurisdiction must develop its own approach to regulatory processes in the field of environment, health and safety. On balance, it is not clear in our view whether Misconceptions about the Causes of Cancer lights the way for Canada. References
Fredrick D Ashbury, PhD Terrence Sullivan, PhD |
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Last Updated: 2005-01-28 |  |
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