November 17, 2020
Delivered via email. Also available in PDF format.
Dr. Norman E. Sharpless, Director, (firstname.lastname@example.org)
National Cancer Institute
9609 Medical Center Drive
Rockville, MD 20850
Douglas R. Lowy, M.D. NCI Principal Deputy Director (email@example.com)
Philip E. Castle, Ph.D., M.P.H., Director, NCI Division of Cancer Prevention (firstname.lastname@example.org)
Jennifer Miller Croswell, M.D., M.P.H., Editor-in-Chief PDQ Screening and Prevention Editorial Board, National Cancer Institute(email@example.com)
Re: The inclusion of environmental exposures (specifically cancer-causing chemicals) in information about breast cancer risk factors in the Breast Cancer Prevention PDQ on the National Cancer Institute’s website
Dear Dr. Sharpless:
The National Cancer Institute’s (NCI) patient and health professional Physician Data Queries (PDQ) about breast cancer prevention significantly underrepresent a key piece of breast cancer awareness: reducing breast cancer risk related to environmental exposures. For the purposes of this letter, environmental exposure refers specifically to cancer-causing chemicals.
We recognize that NCI is a leading and trusted source of information for all cancer-related considerations. It is because of this leadership role that we believe it is especially important for NCI to be a leader in educating health care providers, cancer patients and the general public about a significant body of evidence linking environmental exposures to breast cancer risk. The undersigned organizations and individuals therefore respectfully ask NCI to update its publicly available information about breast cancer risk and prevention to reflect current scientific understanding of these potential risks.
We understand that summarizing information about environmental risks isn’t easy. Breast cancer risk is complex and develops from interactions between genes, lifestyle and environmental exposures. The risk related to environmental exposures is even more complex as it may also be related to the timing of exposure in a woman’s life. Additionally, people are exposed to numerous chemicals simultaneously, rather than one chemical at a time, as is often the focus in research studies. Despite this complexity, research widely supports reducing environmental exposures when possible. Women want to reduce their breast cancer risk, and women and health care providers deserve the information to be able to take informed, preventative steps.
We are pleased that NCI is welcoming applications for research projects related to environmental exposures. We encourage you to expand this commitment beyond research to also include public information on the NCI website, which currently under-represents knowledge of this topic. The patient PDQ states that “it is not clear” whether the environment affects breast cancer, and also states “Studies have not proven that being exposed to certain substances in the environment, such as chemicals, increases the risk of breast cancer.” The health professional PDQ states “Overall, the epidemiological and animal study evidence that supports an association between breast cancer and specific environmental exposures is generally weak.” These statements are unhelpful and misleading because they don’t communicate the large body of laboratory evidence showing that certain chemicals likely increase breast cancer risk, given that they increase mammary tumors in animal experiments. Challenges to studying environmental chemicals in humans mean that clear evidence of an association may not be obtainable, so the evidence we do have must be shared as an appropriate basis for action.
Numerous other federal agencies support our position that environmental exposures are part of the complex web of breast cancer risk factors that should be acknowledged, studied, and acted on. Examples include:
By NCI’s own standards your agency is underrepresenting concerns about environmental links to breast cancer. The NCI website states that “While increased risk for some cancers is caused by inherited genetic factors (about 5%–10% of cancer cases), most cancers are caused by environmental and lifestyle factors.
Additionally, NCI states that it looks to the National Toxicology Program (NTP) to identify carcinogens, but then does not acknowledge or address the identified chemicals of concern. For example, NTP lists chemicals including ethylene oxide, benzene, 1,3-butadiene and others as having sufficient evidence to be considered mammary gland carcinogens and likely to be human carcinogens. (Benzene and 1,3-butadiene exposures include gasoline and vehicle exhaust. Ethylene oxide is a sterilizing gas, and women have historically been exposed at work, for example, in healthcare). Yet these findings are not reflected in NCI’s PDQs. Importantly, the NTP has limited capacity to test for chemical safety and so its list should not be considered comprehensive.
The NCI site also states that it looks to the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, for lists of known or reasonably anticipated carcinogens. A 2011 review of human carcinogens by IARC lists ethylene oxide and tobacco smoking as “preventable exposures associated with human cancers, as identified by the International Agency for Research on Cancer,” specific to breast cancer. These two exposures are described as “agents with limited evidence in humans,” meaning “that a causal relationship was credible but that chance, bias, or confounding could not be ruled out with reasonable confidence.”
That IARC review goes on to note that “it is also likely that many human carcinogens remain to be identified” and that there are a “large number of probable and possible carcinogens identified by experimental studies.” The authors point to a separate review that “identified more than 200 chemicals that induce mammary gland tumors in experimental animals,” and explain that “most of these have been classified by IARC as carcinogenic, probably carcinogenic, or possibly carcinogenic to humans, but there were too few women in the epidemiological studies to permit conclusions about their potential to cause breast cancer.” The authors suggest that “better linkage between experimental results and human carcinogenicity should lead to the identification of human carcinogens on the basis of experimental results.” In other words, IARC’s limited list of breast carcinogens is attributable to weaknesses in the human research but does not provide reassurance that chemicals that cause mammary tumors are not also human breast carcinogens.
Beyond NTP’s and IARC’s lists, peer reviewed literature is another important source that providers could benefit from being aware of when making decisions concerning health. Examples include:
In accordance with the numerous federal agencies, working groups and documents listed above, women and health care providers would benefit from NCI sharing information on the risk or potential risk of environmental exposures so that individuals, clinicians, and policymakers can take preventive actions. BCERP, for example, recommends that health care professionals educate people on the need to reduce environmental exposures when possible and provides specific examples of actions women can take to reduce their exposure to potentially harmful chemicals. While we believe their recommendations could be even more comprehensive, it demonstrates an important acknowledgement of the need to encourage preventive measures to protect people’s health.
We believe that NCI updating its information and approach to communicating about environmental exposures related to breast cancer risk would have a significant impact on the ability of women’s health organizations and health care providers to offer accurate information to women about their health risks. It would also allow individual women access to useful information to make decisions for their own health and the health of their families.
Based on the above, we ask NCI to implement a more complete approach to describing breast cancer risk linked to environmental exposures and to explain multidisciplinary scientific approaches for identifying risk factors for complex, multifactorial and long-latency diseases like breast cancer. We also request that this information be made available in the PDQs so that individuals, breast cancer/women’s health organizations, and health professionals can better understand the state of the evidence on environmental breast carcinogens. We respectfully ask NCI to do the following:
Studying the relationship between environmental chemicals and cancer is difficult, because it can take decades after an exposure before cancer is diagnosed, and the exposures often are invisible, so patients can’t tell us about them. That’s why scientists rely on a combination of evidence from studies in people and controlled experiments in laboratory animals and cells.
Scientists do know that many chemicals are biologically active in ways that can influence breast cancer. For example, common chemicals cause mammary gland tumors in animals, interfere with the natural hormone estrogen (a known breast cancer risk factor), or disrupt other hormones. Exposure to certain chemicals early in life may disrupt development of the breast in ways that make it more susceptible to cancer later on.
Several panels of expert scientists and physicians recommend avoiding or reducing exposure when laboratory evidence links chemicals to breast cancer, rather than waiting for proof.
Avoiding exposure especially makes sense when an alternative is easy to choose. For example, people can avoid some hormone disruptors by reading product labels to avoid using products with parabens and some pesticides. In many cases, changes in government policies are needed to reduce exposure to chemicals that may increase breast cancer risk, since it can be impossible for individuals to know where these exposures occur or to influence them.
Additionally, NCI should include language from other government efforts that suggest that taking precaution related to environmental exposures may accelerate prevention, even in the absence of absolute proof. Examples from these reports are quoted above.
We believe updating NCI’s approach to evaluating and sharing information about environmental links to breast cancer would provide helpful and actionable advice to the general public about opportunities to prevent risky exposures. It would also support health care providers in their ability to support patients and could serve as an important model for NCI’s overall approach to considering environmental links to other types of cancer.
Thank you for your consideration of these important issues. We look forward to hearing from you about next steps. Further communication on this important matter can be directed to Jayla Burton, Program Officer at Breast Cancer Action (firstname.lastname@example.org).
* For identification purposes only.
 President’s Cancer Panel. 2010. Reducing Environmental Cancer Risk: What We Can Do Now, 2008–2009 Annual Report. U.S. Department of Health and Human Services, National Institutes Of Health, National Cancer Institute. https://deainfo.nci.nih.gov/advisory/pcp/annualreports/pcp08-09rpt/pcp_report_08-09_508.pdf
 Institute of Medicine. 2012. Breast Cancer and the Environment: A Life Course Approach. Washington, DC: The National Academies Press. https://www.nap.edu/catalog/13263/breast-cancer-and-the-environment-a-life-course-approach
 Breast Cancer and The Environment Research Program. 2013. An Overview of Recent Research Findings Applicable to Health Professionals. https://bcerp.org/wp-content/uploads/2016/11/Final-BCERP_Monograph-6-13-13.pdf
 National Institute of Environmental Health Sciences. 2018. Breast Cancer and Risk Factors. https://www.niehs.nih.gov/health/materials/environmental_factors_and_breast_cancer_risk_508.pdf
 Interagency Breast Cancer and Environmental Research Coordinating Committee. 2013. Breast Cancer and the Environment: Prioritizing Prevention. https://www.niehs.nih.gov/about/assets/docs/breast_cancer_and_the_environment_prioritizing_prevention_508.pdf
 National Cancer Institute website. “Environmental Carcinogens and Cancer Risk.” Viewed October 8, 2020. https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/carcinogens
 From a search of The National Toxicology Program’s “Chemical Effects in Biological Systems” database, using the search terms Subjects: Animals and Humans, Organs or Tissues: Breast/mammary gland, and Substance Types: Chemicals and Mixtures. Searched September 23, 2020. https://manticore.niehs.nih.gov/roc Also available at: National Toxicology Program. 2016. Report on Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. Department of Health and Human Services, Public Health Service. https://ntp.niehs.nih.gov/go/roc14
 Cogliano VJ, Baan R, Straif K, et al. Preventable exposures associated with human cancers. J Natl Cancer Inst. 2011;103(24):1827-1839.
 Rudel RA, Attfield KR, Schifano JN, Brody JG. Chemicals causing mammary gland tumors in animals signal new directions for epidemiology, chemicals testing, and risk assessment for breast cancer prevention. Cancer. 2007 Jun 15;109(12 Suppl):2635-66.
 Rudel RA, Ackerman JM, Attfield KR, Brody JG. 2014. New exposure biomarkers as tools for breast cancer epidemiology, biomonitoring, and prevention: a systematic approach based on animal evidence. Environ Health Perspect 122:881–895.
 Schwarzman MR, Ackerman JM, Dairkee SH, Fenton SE, Johnson D, Navarro KM, Osborne G, Rudel RA, Solomon GM, Zeise L, Janssen S. Screening for Chemical Contributions to Breast Cancer Risk: A Case Study for Chemical Safety Evaluation. Environ Health Perspect. 2015 Dec;123(12):1255-64. doi: 10.1289/ehp.1408337. Epub 2015 Jun 2. PMID: 26032647; PMCID: PMC4671249.
 Madia F, Worth A, Whelan M, & Corvi R. (2019). Carcinogenicity assessment: Addressing the challenges of cancer and chemicals in the environment. Environment international, 128, 417–429. https://doi.org/10.1016/j.envint.2019.04.067
 Ohayon JL, Nost E, Silk K. et al. Barriers and opportunities for breast cancer organizations to focus on environmental health and disease prevention: a mixed-methods approach using website analyses, interviews, and focus groups. Environ Health 19, 15 (2020). https://doi.org/10.1186/s12940-020-0570-7
 Breast Cancer and The Environment Research Program. 2013. Girls, The Environment, and Breast Cancer Risk: A health professional’s guide to educating patients and parents about breast cancer risk reduction. https://bcerp.org/wp-content/uploads/2016/10/1386_NIEHS_BCERP_Healthcare_Toolkit_Final_PC-1.pdf
 See the National Toxicology Program’s “Chemical Effects in Biological Systems” database, using the search terms Subjects: Animals and Humans, Organs or Tissues: Breast/mammary gland and Substance Types: Chemicals and Mixtures. Available at https://manticore.niehs.nih.gov/roc Also see NTP (National Toxicology Program). 2016. Report on Carcinogens, Fourteenth Edition; Research Triangle Park, NC: U.S. Department of Health and Human Services, Public Health Service. https://ntp.niehs.nih.gov/go/roc14
 Cogliano VJ, Baan R, Straif K, et al. Preventable exposures associated with human cancers. J Natl Cancer Inst. 2011;103(24):1827-1839.
 Institute of Medicine. 2012. Breast Cancer and the Environment: A Life Course Approach. Washington, DC: The National Academies Press.