Cancer is mostly thought of as being caused by smoking, heriditary genes, and personal lifestyles. It is a tendancy to ignore the fact that environmental and chemical exposure may be a larger cause of cancer.
Cancer: 101 Solutions to a Preventable Epidemic, Guy Dauncey, Liz Armstrong and Anne Wordsworth. Paperback, 336 pgs, New Society Publishers, 2007. ISBN: 9780865715424. $27.95
“Paradigm” is a useful word that describes a predominant theory and the assumptions that underpin it. Paradigms are a bit like the gospels — they are believed and rarely questioned.
In the medieval world, everyone assumed that the Sun revolved around the Earth. When Copernicus and Galileo challenged the paradigm with new evidence, their ideas caused a huge furor, but over time they opened up a whole new approach to science and astronomy.
Paradigms never shift easily, since their believers hold onto them in spite of evidence that ought to make them crumble. When paradigms do shift, however, a flood of creativity is released, and changes occur with great speed.
We believe that a paradigm shift is long overdue in our understanding of cancer.
The conventional cancer paradigm claims as its foundation a 1981 report, commissioned by the US Congress and written by two British scientists, Richard Doll and Richard Peto, called The Causes of Cancer: Quantitative Estimate of Avoidable Risks of Cancer in the United States Today. This attributed about 65% of all cancers to tobacco smoking and diet and virtually dismissed environmental and occupational threats.
The report was enthusiastically embraced by many, including the conservative cancer establishment of the time, and went on to become the gospel of cancer causation in epidemiology textbooks, public health and medical schools nearly everywhere.
The political context is important. Doll and Peto’s report was released early in President Ronald Reagan’s first term, when deregulation was the new creed and environmental protection was coming under fierce attack. Much of the energetic cancer prevention activism of the 1960s and 70s, epitomized in books such as Silent Spring and Dr. Samuel Epstein’s Politics of Cancer, faded to near oblivion.
Most traditional cancer prevention programs therefore urge us to change our personal habits — stop smoking, eat more fruits and vegetables, and so on. This is good advice, but it’s limited. Very little attention is focused on toxic substances that are known or suspected to cause cancer.
Doll and Peto’s analysis looked only at deaths, not the incidence of cancer. In their analysis of occupational cancers, they excluded anyone over 65 due to the non-availability of systematically collected data, even though more than 70% of cancers were occurring after 65. They excluded African Americans, and they ignored the steady increase in cancer among children and young people. Their work, based chiefly on epidemiologic evidence, ignored animal and other laboratory studies that would have demonstrated likely harm, and did not address the multi-factorial nature in which carcinogens and other risk factors combine.
As a result, they seriously underestimated the role of environmental pollution. They based their 1981 research on just 16 known carcinogens, whereas in 2006 the International Agency for Research on Cancer listed 414 known or suspected carcinogens.
Doll and Peto’s document, and others that fall into the “cancer-is-a-lifestyle-disease” genre, fail to consider many new factors, including the role played by hormone mimics, the timing of exposure to hazardous substances, our growing body burden of chemical contamination and the role of multiple interacting exposures. In August 2007, for instance, researchers found that women who were exposed to relatively high levels of DDT before the age of 14 were five times more likely to develop breast cancer later in life than women with lower exposures.
In 2006, it was disclosed that Doll had a long-term financial relationship between 1970 and 1990 with Monsanto, as well as receiving payments from the American Chemical Council, ICI, Dow, the asbestos industry, and General Motors.
Doll and Peto’s work should no longer be used as an explanation of the causes of cancer. It’s time to embrace a new paradigm, incorporating the latest knowledge.
***
[From WS September/October 2007]