Phthalate biomarker concentrations did not result in an increased risk of developing invasive breast cancer, according to results from a prospective subgroup analysis of women enrolled in the Women’s Health Initiative (WHI).1 

Although the study authors didn’t observe a large increase in invasive breast cancer risk as concentrations of phthalate biomarkers increased, they also “weren’t able to completely rule out a smaller effect on breast cancer risk,” said Katherine W. Reeves, PhD, MPH, of the University of Massachusetts Amherst, who is the study’s corresponding author. “There’s still significant work that needs to be done in this area.” 

This includes looking at premenopausal women and whether exposure could affect breast cancer risk in these women, as well. 

Phthalates are endocrine-disrupting, and their effects on the human reproductive system has been of great interest. In humans, the primary exposure to phthalates is through food and beverages wrapped in plastic; in vitro studies have suggested that certain phthalates may be associated with breast cancer.2

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Historically, women have had slightly higher exposures to phthalates than men, but the increased use of phthalates can be found in “everything from personal care products to industrial adhesives and building materials,” according to Breast Cancer Prevention Partners, so “everyone is equally at risk for exposure.”3

“There is a growing appreciation for the fact that breast cancer risk is really accumulated across the lifespan and that in particular, early stages such as in adolescence or before somebody’s first pregnancy might be extremely important windows of susceptibility to accumulating breast cancer risk,” said Dr Reeves. “We weren’t able to evaluate any of that in this study,” she added.

While the link between phthalates and breast cancer may not be as strong as, for example, smoking and lung cancer, “it does not mean there isn’t a smaller effect,” she said.