by In April 2010, The President’s Cancer Panel (PCP) issued a report entitled “Reducing Environmental Cancer Risk: What We Can Do Now.” In their opening letter to the President, the authors state, “The Panel was particularly concerned to find that the true burden of environmentally induced cancer has been grossly underestimated. With nearly 80,000 chemicals on the market in the United States, many of which are used by millions of Americans in their daily lives and are un- or understudied and largely unregulated, exposure to potential environmental carcinogens is widespread.”
At the time the report was made public, many of us in cancer advocacy were hopeful that more attention would be focused on environmental links to cancer development and thereby on primary prevention.
So what has happened in the decade since this report was issued? What progress have we made and what challenges still exist?
In October 2020, an article published in the American Association for Cancer Research’s journal Cancer Epidemiology, Biomarkers & Prevention sought to address these questions. “Rethinking Environmental Carcinogenesis” lays out recent advances in the study of environmental links to cancer development, the challenges researchers face in more rapid progress, and what can be done going forward to ensure this kind of research is successful in reducing the burden of cancer. This is a brief overview of that article and references the original PCP report findings.
What We Know
To begin, when we use the word “environmental” in relation to cancer causation, we mean anything we drink, eat, breathe or put on our bodies. It’s important to understand how that broad definition has such a large impact on the possibility of anyone of us developing cancer. Think for a moment about all of the exposures you have in a day – from your drinking water and food, to the soap or shampoo you use, to the quality of the air you breathe where you live. Think also of the duration of these exposures over your lifetime. Connecting the dots between each of those exposures and a cancer development is nearly impossible.
The 2010 PCP report made clear that there is a common misconception that the chemicals to which we are exposed, and those which we purposefully use in our daily lives, have been vetted and found to be safe. It is a misconception that they are all closely monitored and regulated. At the time of the report, only a few hundred of the 80,000+ chemicals in daily use in the US had been tested for safety. The PCP authors point out that our regulatory actions are primarily “reactionary,” not “precautionary,” and that the public, not industry, bears the burden of providing evidence of harm from an environmental exposure before action is taken.
We have learned that chemicals can act in a variety of ways that may promote cancer. At the most basic level, many of us are aware that carcinogens (things that cause cancer) can damage our cells. But researchers have identified other ways, or pathways, by which chemicals can cause cancer. Among these are immunosuppression, chronic inflammation and endocrine disruption. We have also learned there’s a possibility that the combination of exposures to different chemicals could be a culprit in the development of cancer, even if there is little evidence of a single compound being causative. And we’ve learned quite a bit about how the timing of exposures may play a key role in the development of cancer (known as Windows of Susceptibility).
In the 1950s and ‘60s, the study of cancer-causing chemicals was a major focus in research, using rodent models. In the 1970s, a new focus on the role of viruses “overshadowed” that work. By the 1980s and ‘90s, the focus turned again to genetics and by the 2000s, much work involved key hallmarks of the cancers themselves that could be exploited as targets for treatment – not prevention. While there continues to be exciting work in many areas of understanding how cancer develops, the study authors state “there is growing concern that the current emphasis in cancer research on treatment has stalled progress in both primary and secondary cancer prevention.”
What we know is that in addition to early detection, primary prevention via reduced exposure to environmental carcinogens is critical in our efforts to reduce cancer incidence and death.
Recent Advances
New concepts being integrated into the study of environmental links to cancer include not only genetics, determining the early effects of exposure and how those exposures can operate in ways beyond DNA damage that causes a genetic mutation, but also health disparities.
Studies have shown higher rates of certain cancers in groups of people who live or work in places where they may be exposed to higher concentrations of harmful chemicals. For instance, rates of childhood leukemia vary based on where children live. If they live closer to freeways or industrial areas, they are more likely to develop leukemia than children living where air pollution is lower. Workers employed in construction, agricultural or janitorial fields tend to have an increased risk for certain cancers. A challenge in this line of research, however, is recruitment and retention of study participants.
Technological advances have improved researchers’ abilities to measure early markers of exposure to carcinogens, helping to explain how cancers develop. Other advances have allowed researchers to predict whether a compound has the potential to be carcinogenic.
Research into endocrine disrupting chemicals (like BPA) has led to new information about the importance of the timing of exposure to chemicals during certain periods of a person’s lifespan – beginning in utero. (Windows of Susceptibility studies were a focus of the Breast Cancer and the Environment Research Program. Read more about that program here. The Wisconsin Breast Cancer Coalition was a partner in this program from 2010-2015.)
A growing concept in research is the idea that mixtures of chemicals can behave in ways that increase the likelihood of producing cancer. For instance, chemicals that aren’t considered carcinogenic by themselves could produce cancer when combined or, chemicals thought to be “safe” could actually be classified as “harmful” because they create an environment in which cancer could develop. The article’s authors point out that because most studies are on the role of single chemicals as possible carcinogens, these new findings “raise the need for continued research on the combined action of chemical mixtures at low doses – studies that better mirror the exposure environment in which we all live.”
Challenges
Cancer research happens in the lab, of course, but translating lab findings into prevention strategies in our communities and personal lives is another challenge. First, the methodology of conducting the kinds of large human studies needed is a challenge. These studies are expensive and take a long time to conduct in order to be done properly.
The authors point out the challenge of dealing with the sheer number of chemicals and their combinations. While there is clear evidence that some chemicals are carcinogenic, the evidence is less clear for thousands of others. It’s considered critical then that researchers continue work on assessing the potential for harm from certain chemicals, develop risk reduction strategies, and “communicate across institutional and disciplinary siloes” about the evidence that exists.
On the “institutional” side, the article notes at least eight federal agencies that need to work together here. There are regulatory agencies such as the Environmental Protection Agency, the Consumer Product Safety Commission, the Food and Drug Administration and the Occupational Safety and Health Administration. Agencies like the Centers for Disease Control and Prevention work in the area of health promotion. Research is conducted at the National Institutes of Health (and its constituent institutes like the National Cancer Institute and the National Institute of Environmental Health Sciences) and through the National Toxicology Program.
On the “disciplinary” side, the article points to scientists working on the biology of cancer versus those working in environmental health. Into this mix, the powerful influence of outside forces (such as industry) and the role they play with policy makers complicates a unified response to the problem.
Finally, the authors describe the difficulty of having evidence that risk reduction strategies work when “We will never know the faces of people whose cancer has been prevented.” Research involves endpoints that reveal success. While lower incidence rates may result from reduced exposures, these will take a long time to see and in the meantime, prevention strategies become harder to encourage or enforce. People tend to lose interest when there isn’t an immediate result to an intervention.
What’s Ahead
It is clear that action on reducing environmentally linked cancers will not be accomplished by one discipline alone. It will take the commitment of many stakeholders, including research funders, scientists, the public health sector, policymakers, cancer advocates and community leaders. The authors present five areas of opportunity.
- Prioritize chemicals that should be reduced despite the lack of absolute evidence of harm. Invest in tools that help characterize chemicals of concern and strengthen regulation.
- There needs to be increased funding in this specific area of cancer research or actionable research will lag and new scientists will not be attracted to this field.
- Cross disciplinary engagement by scientists of genetics, molecular biology, toxicology, epidemiology and exposure assessment. There is great opportunity in the collaboration of cancer researchers across fields of study.
- Community Advocacy. This is us! If you’re reading this, you are already taking a step towards advocacy. We bring the perspective of people touched by cancer to researchers, public health agencies and policy makers. There are many ways in which we can use our voice to positively influence these other stakeholders.
- Evidence-informed action. There needs to be better understanding and dialogue among researchers, regulatory agencies and policy makers about how strong evidence must be before action is taken to reduce exposures. Clinical studies such as “gold standard” double blinded randomized control studies are not feasible in human studies of environmental exposures. First of all, there’s no “control” group to be had. We’ve all been exposed to multiples of these compounds. And ethically, we can’t purposely expose participants to a chemical that may be harmful.
This last point is critical. As noted earlier, our regulatory response to chemicals of concern has been “reactionary.” This can’t be considered a successful strategy. It isn’t working. And so, as the authors state, we should communicate what we DO know about the effects of certain chemicals on the development of cancer, report the results of both animal and human studies and allow people to contribute to the decision making process. We can use the information we do have to both encourage a better regulatory response (at both the state and federal levels) and to make decisions on a personal level that may reduce our risk. As advocates, that means educating ourselves and using our voices for positive change.