Identifying disease clusters is one way environmental health advocates have been able to link the causation of cancer to releases of toxic chemicals in the environment. According to the National Cancer Institute, a disease cluster is “the occurrence of a greater than expected number of cases of a particular disease within a group of people.” The study of disease clusters can help to shed light on the environmental roots of a disease because, for example, if a type of cancer is occurring at a rate higher than average in a particular community, then it is more likely there is an environmental, and not genetic, cause.
Hollywood has made cancer clusters famous in movies. For example, in Erin Brockovich, attorneys successfully identified and fought to stop contamination of drinking water with hexavalent chromium, which allegedly caused an increased rate of cancer in Hinckley, Calif. And in A Civil Action, plaintiffs received a settlement for the contamination of Woburn, Mass. water supplies with trichloroethylene (TCE) after a high incidence of leukemia was discovered in the town.
Sandra Steingraber highlights cluster studies in her book Living Downstream and explains why public health officials remain skeptical of cluster studies. First, because cluster studies are usually done in single, small communities, it is more difficult to prove that cancer is not occurring merely by chance. Cancer rates in these communities must reach very high levels before the study can be deemed “conclusive” and therefore actionable.
A second problem with cancer cluster studies is that there is no unexposed control group. The adage “a rising tide sinks all ships” is apt: if the people in the background are also contaminated, it is more difficult to see differences.
Despite the difficulties inherent in cluster studies, they remain one of the only ways to identify common, environmentally-related causes of cancer. Unfortunately, there is little support for such studies. Governmental actors lack financial resources to undertake studies and to continue investigating when an initial inquiry is inconclusive.
Because of the lack of governmental support for disease cluster studies, environmental advocate Erin Brockovich testified (PDF) before the Senate in 2011 in support of the Strengthening Protections for Children and Communities From Disease Clusters Act. The legislation improved coordination among federal agencies in determining whether a cluster exists and to increase federal funding to affected communities. Brockovich stated that people from around the country contacted her about increases in disease incidences in their communities. Shortly thereafter, the NRDC released a report documenting 42 disease clusters in 13 states. The entire Senate Environment and Public Works Committee endorsed the legislation in 2011, but the bill never came up for a vote in the full Senate.
Senators Barbara Boxer (D-Calif.) and Mike Crapo (R-Idaho) re-introduced the legislation in the Senate on January 22, 2013, to improve coordination among federal agencies in determining whether a cluster exists and to increase federal assistance to affected communities. The bill (PDF) is called Trevor’s Law in recognition of cancer survivor Trevor Schaefer, who was diagnosed with a brain tumor at age 13 in 2002. After learning that there had been four other brain cancer diagnoses in the same year in his tiny Idaho town of 1,700, Trevor and his family began advocating for more support for disease cluster studies.