New Study Suggests Link between Cape Water Supply, Breast Cancer Risk
Upper Cape Cod drinking water that was contaminated by wastewater effluent dating to the 1960s may be associated with an increased risk of breast cancer, a team of BUSPH researchers reports in a new study published online in Environmental Health Perspectives.
The researchers found that associations were strongest for women exposed to contaminated water from the Barnstable Water Pollution Control Facility, versus those not exposed, when a 20-year cancer latency period was assumed. Investigating environmental risk factors for breast cancer poses a challenge because exposure may have occurred years prior to the cancer being diagnosed, known as latency.
“Using a detailed exposure assessment, we found an association with breast cancer with longer latency and greater exposure duration,” the study says. “The current exposure analysis expands upon our earlier work to explore the spatial and temporal relationship between a source of environmental contamination and a route of exposure for this study population.”
BUSPH epidemiology and environmental health researchers have been investigating possible reasons for elevated cancer rates in the upper Cape for decades, recently incorporating extensive spatial and temporal modeling. Among the possible risk factors that they and other researchers have examined are air and water pollution associated with an area military base, pesticide applications to cranberry bogs, particulate air pollution from a large electric power plant, and contaminated drinking water. Some positive links have been made, but researchers have concluded that the environmental exposures they have investigated can explain only a portion of the high cancer incidence.
In 2008, a study led by Veronica Vieira, associate professor of environmental health, found areas of elevated breast cancer risk, including one near the Massachusetts Military Reservation, previously known as Otis Air Force Base, from 1947 to 1956. Last October, a study led by Ann Aschengrau, professor of epidemiology, found that babies born to Cape women exposed to a chemical solvent used in drinking water pipes — PCE, or perchlorethylene — had an increased risk of some birth defects.
In the new study, researchers looked at residential histories, public water distribution systems and groundwater modeling to explore possible associations between drinking water contamination and breast cancer. Exposure was assessed from 1947 to 1993 for 638 breast cancer cases that were diagnosed from 1983 to 1993 and 842 controls, taking into account residential mobility with respect to the drinking water source.
The findings showed no significant associations between drinking water and cancer rates for those who were exposed for less than five years. Adjusted odds ratios for those who had up to 10 years of exposure were slightly increased, compared to women with no exposure. The strongest associations were for women who were exposed to the drinking water for longer time periods, assuming a 20-year latency period to breast cancer diagnosis.
When cancer clusters are discovered, there are many possible environmental factors that could be investigated, said the researchers, led by Vieira. This study, given the geographic overlap of groundwater plumes identified using spatial analyses, investigated the hypothesis that exposure to drinking water contaminated by effluent from a wastewater treatment facility was associated with breast cancer. The spatial relationship alone did not establish exposure, but the study was able to determine a plausible route of exposure by also taking time into account.
In addition to Vieira, researchers on the study included Aschengrau, Thomas Webster, associate professor of environmental health, and Lisa G. Gallagher, currently a postdoctoral fellow at the University of Washington.
The research was supported by grants from the National Cancer Institute and the Superfund Research Program, National Institute of Environmental Health.
The full study can be accessed on the Environmental Health Perspectives website.
Submitted by Lisa Chedekel