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Cancer and the Environment: A Symposium Report by Ted Schettler

Cancer and the Environment:

A Symposium Report


Ted Schettler

April, 2019


Worldwide more than 17 million people were diagnosed with cancer in 2018 and nearly 10 million died from it. Policies and programs addressing smoking, insufficient physical activity, alcohol, diet, overweight and obesity, and certain infections could prevent a significant proportion of cases, and these have been the primary focus of prevention efforts, usually as advice to individuals urging them to change their behavior. While these risk factors point to well-established opportunities to lower risk, they do not fully explain the incidence and trends of many kinds of cancer. Unfortunately, aside from tobacco and alcohol, most cancer prevention programs ignore exposures to cancer-causing chemicals and pollutants in consumer products, homes, workplaces, and the general environment. 

Advocates for addressing environmental risk factors for cancer often encounter resistance. The reasons vary but are most often traced to analyses, beginning more than 35 years ago, estimating that only a few percent of cancers are attributable to occupational or environmental exposures. The original 1981 analysis by Doll and Peto was limited to cancer mortality in people between ages 35-65 yrs., did not address cancer incidence and excluded African-Americans. Although the authors recognized data gaps, the limits of their estimates, the many assumptions underlying them, and that advances in understanding cancer biology might change them substantially, the idea that cancer risk and prevention are overwhelmingly dependent on individual behavioral choices was firmly established.

Today, many mainstream cancer organizations, including the American Cancer Society, follow that tradition. They conclude that occupational and environmental exposures explain little of the cancer burden and fear diluting their main messages about individual behavioral choices by drawing attention to environmental risk factors over which individuals have little control. But this view is not universally held. In 2010 the President’s Cancer Panel issued their report to the President and the National Cancer Institute, Reducing Environmental Cancer Risk: What We Can Do Now, in which they focused on industrial, occupational, and agricultural chemical exposures, indoor/outdoor air pollution, water contamination, nuclear fallout, radiation, and electromagnetic fields.  They said, “The previous estimates [of environmental causes of cancer] are woefully out of date…and underestimate significantly the true toll of cancer related to these exposures.” Not content with just calling for more research, the panel also strongly recommended additional action, based on what we already know. 

Several years ago a diverse group of individuals and organizations came to together to form the Cancer Free Economy Network, (CFEN) premised on “the belief that the water we drink, the air we breathe, the food we eat, the places we work, and the products we use every day should not make us sick.” Representing the Science and Environmental Health Network, I participate in CFEN’s health and science node. The CFEN focuses primarily on cancer-causing environmental chemicals and pollutants while recognizing the importance of other established risk factors and complex interactions among them that, collectively, create the conditions out of which cancer patterns arise. It is this multi-level eco-social model that I previously explored in The Ecology of Breast Cancer, recognizing that breast cancer patterns arise in large part out of conditions that we collectively create in communities and society at large

A group of organizations,  led by University of Massachusetts-Lowell and including the University of Pittsburgh’s Hillman Cancer Center, the School of Public Health, the Allegheny County Medical Society, CFEN and others convened a day-long meeting in Pittsburgh PA on Jan. 29, 2019 titled “Cancer and the Environment Symposium: Priorities for Research, Policy and Clinical Practice”.  The goal was to address occupational and environmental contributors to cancer risk and take a fresh look at opportunities for cancer prevention.  The agenda, slides and videos of each presentation are publicly available online.  Each presenter was asked to provide specific recommendations for research, policy, and practice to be incorporated into the symposium record.

In the opening session, “Setting the Context”, my topic was Cancer: multifactorial diseases requiring multifactorial interventions for prevention.  It was an opportunity to reflect on the concept of causation and how we think about parsing cancer risk among individual risk factors as if they were largely independent. Multi-level cancer risk factors, including environmental agents, are not neatly separated from one another. Interactions among them make it particularly difficult to identify “the cause” of cancer in an individual or in populations. Progress in understanding cancer biology shows that known carcinogens have a wide range of biologic activities, and many common environmental chemicals can trigger what are widely known as “hallmarks of cancer.”  With few exceptions, this information has had little influence on cancer prevention programs, policies, and practice.  

Throughout the day we heard from clinicians, scientists, public health officials, community leaders and others in information-rich presentations and panel discussions. A plan developed at the end of the day and further refined in follow up teleconferences should assure ongoing momentum for additional action to prevent cancer in the region. Most of the presentations at the symposium are directly relevant to topics concerning communities throughout the US and internationally. We encourage you to take a look at the agenda, the presentation slides and videos that may be of interest.  Feel free to share them with others. Comprehensive cancer prevention requires more than attention to individual behaviors. Look for opportunities and responsibilities in the workplace, community and society at large as well.




Kayhla Cornell