Disease clusters, defined as aggregations of diseases in space and/or time at a level perceived to be greater than chance, are commonplace. Such potential clusters are often postulated to be the result of a common source of exposure that may be present in the environment, community, or workplace. Often straightforward, preliminary analyses can resolve the question of whether a cluster exists, however in some circumstances a comprehensive epidemiologic, statistical, and exposure investigation may be required to confirm whether a true cluster exists and could be related to some type of environmental exposure.
Exponent epidemiologists, biostatisticians, industrial hygienists, and environmental scientists have been directly involved on numerous disease clusters investigations. Our teams of scientists have evaluated reports of increased occurrences of disease in the workplace, community, and environment. We have conducted epidemiologic investigations to assess potential workplace and community cancer clusters and we have provided consulting regarding potential clusters of reproductive outcomes such as birth defects or spontaneous abortions.
Our staff can apply state-of-the-art mapping and statistical tools to characterize the spatial patterns of disease occurrence.
Our investigations typically address the following types of questions:
- Are the rates of disease greater than expected in person, place, and time?
- If the observed rates of disease are greater than expected, is there documented exposure that could explain this cluster?
- Does the proposed exposure reflect a biological plausible relationship between exposure and disease outcome?
- Are there alternative explanations for the perceived cluster of disease?
- Are there specific sub-groups that may or may not be at an elevated risk of disease?
Are improvements needed in the workplace or environmental health surveillance systems to accurately characterize potential clusters?
Public health concerns regarding potential environmental-related disease clusters often must be evaluated and communicated about in an atmosphere of tension and anxiety. Public health agencies, industrial facility management, and other stakeholders must strike a balance in addressing community concerns and in conducting the appropriate level of scientific study. Exponent health scientists can help to identify the appropriate scientific approach, implement relevant data collection, analyze available health data and communicate study findings to stakeholders.
Publications/Reports – Disease Cluster Evaluations
Alexander DD. An environmental cause of orofacial cleft defects or an unexplained cluster? South Med J. 2007 Jun; 100(6):553–534.
Buffler PA, Kelsh MA, Kalmes RL, Lau E, Chapman PC, Wood S, Brorby G, Silva M, Hooper C, Rizzo B, Wood R. A nested case-control study of brain tumors among employees at a petroleum exploration and extraction research facility. J Occup Environ Med 2007; 49:791–802.
Buffler PA, Kelsh MA, Chapman P, Wood S, Lau E, Golembesky A, Wood R, Kalmes R, Brorby G. Primary brain tumor mortality at a petroleum exploration and extraction research facility. J Occup Environ Med 2004; 46:257–270.
Kelsh MA, Lau E, Barnard JC, Mandel JS. 2004 Cancer Mortality Among Residents of a Northern California Community Living Near a Hydraulics Manufacturing/Chromium Plating Facility.