University of Vermont

Study Examines Potential Link between Environmental Exposures and Breast Density

Brian Sprague, Ph.D.
University of Vermont Assistant Professor of Surgery Brian Sprague, Ph.D. (Photo by Raj Chawla, UVM Medical Photography)

Your blood is like an internal mirror of what your body absorbs. Through different tests, laboratory specialists can determine your level of cardiovascular risk (cholesterol), diabetes risk (glucose), organ function, as well as environmental exposures. Recent research by Brian Sprague, Ph.D., University of Vermont assistant professor of surgery, and colleagues at the University of Wisconsin, sheds light on a potential correlation between chemicals commonly found in the environment and mammographic breast density, which is associated with a higher risk for breast cancer.

“We wanted to find out if people with different exposure levels had signs of higher or lower risk,” explains Sprague, who works in UVM’s Office of Health Promotion Research and is a member of the Vermont Cancer Center. He and the research team first screened participants’ blood for eight chemicals, including phthalates, parabens and phenols, and then examined how those chemicals were associated with mammographic density. They found that higher serum levels of two chemicals in particular – monoethyl phthalate and bisphenol A (BPA) – were associated with higher breast density. Monoethyl phthalate is a stabilizer found in soaps and shampoos; BPA is an industrial chemical found in plastics.

While this issue has been examined in cells and animal models, Sprague and colleagues’ study results were among some of the first evidence in humans of potential harm from these environmental chemicals.

These elements are commonly detected in all humans, according to Sprague. The Centers for Disease Control and Prevention has found that these chemicals are detectable in more than 90% of Americans.

A total of 264 women, 55 to 70 years old, participated in the study, providing blood samples and undergoing mammography. Breast density on a mammogram is typically categorized as almost entirely fat, scattered (a greater presence of fibroglandular tissue), heterogeneously dense, or extremely dense.  Sprague and his colleagues used specialized computer software to measure breast density more distinctly. The software features a continuous scale – zero to 100 percent – for looking at the brightness of the mammogram, and allowed the scientists to detect differences – such as a 22 percent density versus a 20 percent density – more accurately.

“It was a small study, but it showed that there’s something to be concerned about,” Sprague says. The research needs to be done on a larger scale to confirm the inference. “The ideal would be to collect blood samples over a longer period of time – like 20 years. This is more of a warning sign that we should look further here,” he adds.

Sprague has conducted other studies focused on the influence of sex hormone levels and breast density, as well as vitamin D and breast density. He leads the Vermont Breast Cancer Surveillance System, established in 1994 by Professor of Family Medicine Emerita Berta Geller, Ed.D., and one of only five breast cancer screening registries in the country.

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