Urinary Levels of Endocrine-Disrupting Chemicals and Breast Density in Young Women

Abstract Background: Endocrine-disrupting chemicals (EDCs) found in many household and personal care products have hormonal properties and effects on the mammary gland. It is unclear whether urinary concentrations of EDCs are associated with higher percent breast density, a major risk factor of breast cancer. Methods: We conducted a cross-sectional study of 97 college-aged women. We quantified individual levels of bisphenol A, bisphenol S, bisphenol F, triclosan, triclocarban, 3-benzophenone, seven phthalate metabolites, four parabens, and two other phenols in three 24-hour urine samples combined into a single pooled sample. Each woman had non-enhanced magnetic resonance imaging (MRI) to assess percent breast density. Associations between estimated concentrations of individual EDCs and percent breast density were analyzed using adjusted linear regression. Results: There was no evidence of statistically significant increases in mean percent breast density in the middle or highest tertile for any EDC measured. There was a suggestion that the mean percent breast density was elevated in individuals in the middle and highest tertile level of ethyl-paraben compared to those in the lowest tertile, with a relative increase in mean percent breast density of 16% (β ̂=1.16, 95%CI: 0.92-1.46) in tertile 2 and 24% (β ̂=1.24, 95%CI: 0.99-1.57) in tertile 3, relative to tertile 1 (ptrend=0.07). Similar trends in percent breast density were observed for methyl-, propyl-, and butyl-paraben. Conclusions: Urinary levels of EDCs were not associated with percent breast density in college-aged women. Impact: The estimated effect of EDCs on the breast tissue of young women is unclear and warrants larger studies.