The Biggest Cancer Clusters In History

Spikes in cancer, or cancer clusters, occur when a high number of people in a small geographical area experience similar ailments over a short period of time. Some cancer clusters have possible causes, although investigating and discovering those causes can take years. Current cancer clusters are breaking out everywhere from small Canadian towns to booming cities like San Francisco. Given different places so frequently have radically different cancer rates, the outbreaks below have been subject to a heavy amount of research, investigation, and public scrutiny. 

How do cancer clusters form? Unfortunately, investigations rarely lead to a clearer understanding of what causes cancer in certain areas. While researches sometimes uncover a lack of corporate oversight, the scientific community still has a limited understanding of cancer itself. This means, despite the myriad theories about what causes cancer, causes often remain ambiguous especially due to the lack of common factors between clusters. Many places where cancer is common are positioned near plants or factories that produce harmful chemicals, but other areas are desolate and isolated. Unfortunately, pending major breakthroughs in cancer research, how and why high cancer rates occur in specific areas will largely remain a mystery. 

Photo: user uploaded image

  • Shannon, Quebec Cancer Outbreak

    Date: 1997 - Present 

    Type of Cancer: Various, including kidney cancer, brain cancer, liver cancer, and non-Hodgkin's lymphoma 

    Areas Affected: Shannon, Quebec 

    Cause: Residents in Shannon, Quebec are 249 percent more likely to develop cancer than the average population. This includes cancers that are usually rare, such as brain cancer. A commonly used degreasing agent, TCE, seeped into the groundwater in Shannon around 1997. TCE levels in Shannon are 180 times higher than is considered acceptable by Canadian health standards. There is an ongoing legal battle over the TCE exposure, with multiple residents of Shannon demanding acknowledgment and compensation from the federal government. 

    Population Affected: Unclear, but the number is well into the hundreds. Estimates have recorded upwards of 500 cancer cases and 200 deaths. 

  • Manatee County Florida Leukemia/Brain Cancer Outbreak
    Photo: Jim Mullhaupt / flickr / CC-BY-NC-ND 2.0

    Manatee County Florida Leukemia/Brain Cancer Outbreak

    Date: 1990s - 2017

    Type of Cancer: Leukemia and brain cancer

    Areas Affected: Manatee County, Florida.

    Cause: Possible soil contamination, but the cause of this cluster remains a mystery. Alumni and faculty members of a high school in Bradenton, Florida were the primary group affected by the cancer outbreak. They began to experience the symptoms of cancer shortly after the original school building was demolished. It's unclear if the building had anything to do with the cancer. While researchers have conducted multiple soil and groundwater tests over the years, they did not discover any clear contaminant. 

    Population Affected: Precise numbers were never recorded, but roughly 500 cases of cancer can be linked to Bayshore alumni and employees. 

  • St. Louis Cancer Outbreak

    Date: 1960s - Present 

    Type of Cancer: Various rare cancers, including appendix cancer, thyroid cancer, and brain cancer 

    Areas Affected: St. Louis, Missouri 

    Cause: As is the case with many cancer clusters, the precise cause is unknown and research is ongoing. During World War II, the United States government hired the St. Louis based company Mallinckrodt Chemical Works to process Uranium in order to develop nuclear weapons. In the mid-1940s, Mallinckrodt began dumping radioactive waste in a creek in north St. Louis. When the creek was rerouted in the '60s as part of a development project, this may have caused widespread contamination of carcinogenic materials throughout the soil and groundwater in St. Louis. 

    Population Affected: The exact number of victims is currently unknown, but some estimates go as high as 544. 

  • New Jersey, Illinois, And Connecticut Bone Cancer Outbreak
    Photo: Kramchang / flickr / CC-BY-NC-ND 2.0

    New Jersey, Illinois, And Connecticut Bone Cancer Outbreak

    Date: 1920s

    Type of Cancer: Osteosarcoma (bone cancer) and leukemia 

    Areas Affected:  Orange, New Jersey, Illinois, and Connecticut 

    Cause: The so called "radium girls" succumbed to cancer via radium poisoning from ingesting large amounts of radium paint while drawing glow in the dark numbers on watch faces. The radium settled into the bones of women working in various Radium Luminous Materials Corporation factories and began to rot them from the inside out. Because the women would ingest the radium, their teeth and jaw bones were the most affected parts of the body.

    Population Affected: Hundreds

  • London Scrotal Cancer Outbreak
    Photo: alh1 / flickr / CC-BY-ND 2.0

    London Scrotal Cancer Outbreak

    Date: 1700s - 1840

    Type of Cancer: Scrotal cancer

    Areas Affected: London, England

    Cause: During the initial stages of the scrotal cancer outbreak, Doctor Percivall Pott devised a theory in which the sweat and soot which mingled on a chimney sweep's scrotum rubbed together for so long that it created warts and lesions. After years of inaction against the medical issue, cancer would take hold of "the testicle, which it enlarges, hardens, and renders truly and thoroughly distempered."

    This was somewhat correct. Modern science has shown that coal contains a carcinogen which is metabolized by the human body that disrupts the human body's DNA replication and creates G mutations. As these mutations begin to copy themselves throughout the body, cancer is created. 

    Population Affected: Hundreds

  • San Francisco Breast Cancer Outbreak
    Photo: davidyuweb / flickr / CC-BY-NC-ND 2.0

    San Francisco Breast Cancer Outbreak

    Date: Approximately 2008 - Present 

    Type of Cancer: Breast cancer and other various forms the disease.

    Areas Affected: San Francisco

    Cause: Firefighters in San Francisco are continuously exposed to dangerous fumes likely caused by the increased amount of synthetic materials in homes. According to the San Francisco Fire Department, 16% of its firefighters are women and 15% of that group has been diagnosed with some form of cancer. This is six times the national average. 

    Population Affected: More than 250 people