A cancer cluster refers to a higher-than-expected number of cancer cases occurring within a specific geographic area or population group during a defined time period.[1] When these clusters occur in communities with known environmental contamination, they raise important questions about potential environmental causes of cancer.[2]
Have breast cancer clusters been documented?
Yes, several communities have reported elevated breast cancer rates in areas with environmental contamination:
- Superfund sites: Communities located near hazardous waste sites designated for cleanup under the federal Superfund program have documented increased cancer rates, including breast cancer.[3][4]
- Groundwater contamination: Areas where industrial chemicals have leached into drinking water supplies have experienced elevated breast cancer incidence in some cases.[5]
- Historical toxic exposures: Regions with legacy contamination from past industrial activities have reported breast cancer clusters warranting investigation.[6]
Why are cancer clusters difficult to investigate?
Several factors complicate the study of cancer clusters and their relationship to environmental exposures:
- Multiple causation: Cancer typically results from complex interactions between genetic factors, lifestyle behaviors, and environmental exposures, making it challenging to isolate single causes.[7]
- Long latency periods: Breast cancer can take 10-30 years or more to develop after exposure to carcinogens, complicating efforts to link cases to specific exposures.[8]
- Population mobility: People move in and out of communities over time, making it difficult to track exposures and outcomes consistently.[9]
- Small numbers: Even legitimate clusters may involve relatively few cases, limiting statistical power to detect associations.[10]
- Background cancer rates: Cancer is common in the general population, so determining whether an apparent cluster exceeds expected rates requires careful statistical analysis.[11]
Have cluster investigations led to important discoveries?
Despite the challenges, some cancer cluster investigations have yielded significant findings:
- Research into clusters has helped identify environmental carcinogens and exposure pathways [12]
- Community-driven investigations have sometimes revealed contamination that authorities had previously overlooked [13]
- Cluster studies have contributed to stricter environmental regulations and cleanup efforts [14]
What should communities do if they suspect a cancer cluster?
If you believe your community may be experiencing a cancer cluster, consider these steps:
- Contact authorities: Report concerns to your state or local health department, which can conduct preliminary assessments
- Document systematically: Gather information about cases, including diagnosis dates, types of cancer, ages, and residential locations (while respecting privacy)
- Engage experts: Seek assistance from environmental health scientists, epidemiologists, and community health advocates
- Request testing: Advocate for environmental sampling of air, water, and soil if contamination is suspected
- Demand investigation: Push for thorough epidemiological investigation by appropriate health agencies
- Organize community: Form or join community groups to coordinate efforts and amplify voices
- Seek remediation: If contamination is confirmed, advocate for cleanup, exposure reduction, and accountability from responsible parties
- Access resources: Contact organizations like the Agency for Toxic Substances and Disease Registry (ATSDR) or environmental justice groups for guidance
Bibliography
[1] Centers for Disease Control and Prevention. “Investigating Suspected Cancer Clusters and Responding to Community Concerns: Guidelines from CDC and the Council of State and Territorial Epidemiologists.” Morbidity and Mortality Weekly Report 62, no. RR-8 (2013): 1-24.
[2] Thun, Michael J., and Tim Sinks. “Understanding cancer clusters.” CA: A Cancer Journal for Clinicians 54, no. 5 (2004): 273-280.
[3] Johnson, Carrie V., Michelle Watanabe-Galloway, Ann M. Austin, and Shinobu Watanabe. “Breast cancer incidence and mortality in the greater Delaware Bay region: investigating a cancer cluster.” Environmental Health 8, no. 1 (2009): S4.
[4] Griffith, James, Ronald C. Duncan, William B. Riggan, and Alfred C. Pellom. “Cancer mortality in U.S. counties with hazardous waste sites and ground water pollution.” Archives of Environmental Health 44, no. 2 (1989): 69-74.
[5] Aschengrau, Ann, David Ozonoff, Deborah Coogan, Robin Vezina, Timothy Heeren, and Yun Zhang. “Cancer risk and tetrachloroethylene-contaminated drinking water in Massachusetts.” Archives of Environmental Health 48, no. 5 (1993): 284-292.
[6] Brody, Julia Green, Ruthann A. Rudel, Maxwell Michels, Robert A. Moysich, Stephanie Bernstein, Joel Attfield, and Janet Gray. “Environmental pollutants, diet, physical activity, body size, and breast cancer.” Cancer 109, no. S12 (2007): 2627-2634.
[7] Hanahan, Douglas, and Robert A. Weinberg. “Hallmarks of cancer: the next generation.” Cell 144, no. 5 (2011): 646-674.
[8] Colditz, Graham A., Karin B. Michels, and Susan E. Hankinson. “Breast cancer: magnitudes of associations and timing of exposures.” Breast Cancer Research 1, no. 1 (1999): 1-4.
[9] Neutra, Raymond R. “Counterpoint from a cluster buster.” American Journal of Epidemiology 132, no. 1 (1990): 1-8.
[10] Rothman, Kenneth J. “A sobering start for the cluster busters’ conference.” American Journal of Epidemiology 132, no. 1 supplement (1990): S6-S13.
[11] Goodman, Michael, Joseph Goodman, and Raymond R. Neutra. “The spatial epidemiology of cancer.” In Spatial Analysis, GIS and Remote Sensing Applications in the Health Sciences, edited by Eric Dummer and Paul Wilkinson, 123-145. Chelsea, MI: Ann Arbor Press, 2000.
[12] Clapp, Richard W., Molly M. Jacobs, and Edward L. Loechler. “Environmental and occupational causes of cancer: new evidence 2005-2007.” Reviews on Environmental Health 23, no. 1 (2008): 1-37.
[13] Brown, Phil, and Edwin J. Mikkelsen. No Safe Place: Toxic Waste, Leukemia, and Community Action. Berkeley: University of California Press, 1990.
[14] Bullard, Robert D., Paul Mohai, Robin Saha, and Beverly Wright. Toxic Wastes and Race at Twenty: 1987-2007. Cleveland: United Church of Christ Justice and Witness Ministries, 2007.
