Bisphenol A and breast cancer: Can mechanistic plausibility be reconciled with epidemiological inconsistency?

This review synthesizes current evidence on the relationship between exposure to the environmental chemical bisphenol A, or BPA, and breast cancer risk. While laboratory studies demonstrate that even low concentrations of BPA can biologically promote breast cancer development and progression by interfering with hormonal signaling, altering cellular epigenetic regulation, and remodeling the tumor microenvironment, findings from large-scale population studies remain inconsistent. We find that many epidemiological studies in adult populations have failed to establish a clear, significant association between BPA exposure and breast cancer risk. However, when investigations use more precise exposure assessment methods, such as measuring the biologically active form of BPA, or focus on exposures during critical life stages such as fetal development or puberty in genetically susceptible subgroups, a significantly increased risk is frequently observed. This suggests that BPA may not pose a uniform risk to all individuals; its impact appears to depend on the timing of exposure, individual genetic susceptibility, and coexposure with other environmental chemicals. Given the strength of the mechanistic evidence and concerns over the potential long-term health consequences of early-life exposure, we conclude that although current human epidemiological evidence is not fully consistent, prudent preventive measures to reduce population exposure to BPA, particularly during sensitive periods such as pregnancy and childhood, are warranted. Future research requires the establishment of longitudinal cohorts that track individuals from early life, utilizing more accurate exposure assessment methods, to ultimately clarify the role of BPA in breast cancer.