Superfund Research Program
Use of Spatial and Temporal Analyses to Provide Insights into the Environmental Etiology of Cancer
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Background: Since 1995, researchers at the SRP at Boston University (BU) have used Geographic Information System (GIS) data and increasingly sophisticated statistical methods to examine the geographical distribution of disease, which can provide important clues to the origins of the disease. These environmental epidemiological studies are complicated by factors including small sample size for case populations; the fact that disease registries only contain data on where people lived at the time of diagnosis, which may not be the time of exposure; and methodological problems of understanding, estimating and evaluating potential biases.
BU SRP research teams, led by Drs. David Ozonoff, Ann Aschengrau, Tom Webster, and Veronica Vieira have developed new approaches that allow them to:
- Map disease "hot" and "cold" spots while accounting for known risk factors such as age and smoking. Using these tools, they identified lung cancer and breast cancer "hot spots" associated with two pollution plumes near the Massachusetts Military Reservation.
- Establish a link between prenatal perchloroethylene (PCE) exposure and adverse birth outcomes including cleft lip and neural tube defects.
- Determine that women living in more northern latitudes may be at greater risk for rheumatoid arthritis.
Advances: Drs. Aschengrau, Webster, and Vieira recently conducted an analysis to test the hypothesis that drinking water contaminated by municipal wastewater effluent from the Barnstable Water Pollution Control Facility (BWPCF) is associated with breast cancer incidence in upper Cape Cod, Massachusetts. Surveys of the wastewater and groundwater found suspected endocrine disruptors, including alkylphenols and other estrogenic phenolic compounds. The BU research approach included methods for analyzing the distribution of disease in both space and time.
The researchers assessed exposure based on three sets of information:
- Residential histories of both the case and control groups. These data identified which participants were living at residences during years when drinking water was impacted by effluent.
- Questionnaire data that identified the drinking water source (public or private) of the participants for each of their residences and whether women ever regularly used bottled water.
- Information on the public water distribution systems, which was used to determine when the drinking water wells were impacted by effluent from the BWPCF.
The researchers began with MODFLOW, a modular software program publicly available from the USGS website, and modified the program to examine historical groundwater movement.
Their groundwater models showed that contamination of drinking water by effluent from the BWPCF was plausible and indicated that effluent from the BWPCF reached drinking water wells as early as 1966. The researchers found statistically significant positive associations between breast cancer and exposure to drinking water impacted by wastewater effluent from the BWPCF. The associations were strongest among women who were not regular bottled water users and among women exposed for long durations when latency periods were taken into account.
Significance: The researchers integrated groundwater modeling, residential mobility, and information about public water systems in GIS to assess exposure to drinking water impacted by wastewater effluent. Their historical groundwater model provided a method to explore the spatial and temporal relationship between a source of contamination and a possible exposure route for study participants.
When cancer clusters are discovered, there are many possible environmental factors that could be investigated. While a spatial relationship alone does not establish exposure, this study was able to determine a plausible route of exposure by also taking time into account. The researchers demonstrated that by incorporating additional data, such as residential histories of the participants and contaminant movement over time, hypotheses generated by spatial analyses can provide additional insights into the environmental etiology of breast cancer.
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To learn more about this research, please refer to the following sources:
- Gallagher LG, Webster TF, Aschengrau A, Vieira VM. 2010. Using residential history and groundwater modeling to examine drinking water exposure and breast cancer. Environ Health Perspect 118(6):749-755. doi:10.1289/ehp.0901547 PMID:20164002 PMCID:PMC2898849
- Vieira VM, Webster TF, Weinberg JM, Aschengrau A. 2008. Spatial-temporal analysis of breast cancer in upper Cape Cod, Massachusetts. Int J Health Geogr 7:46. doi:10.1186/1476-072X-7-46 PMID:18700963 PMCID:PMC2538515
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