Phthalate Exposure and Breast Cancer: A Systematic Review and Meta-Analysis of Epidemiological Evidence

Phthalates are widely used chemicals with endocrine-disrupting properties; however, epidemiological evidence regarding their association with breast cancer remains inconsistent. Therefore, we aimed to synthesize the available epidemiological evidence on the association between phthalate exposure and breast cancer and to quantify these associations through metabolite-specific meta-analyses. We conducted a systematic review and meta-analysis of epidemiological studies identified in PubMed, Web of Science, EBSCO, and LILACS up to 1 June 2026. We performed metabolite-specific meta-analyses using random-effects models, comparing the highest and lowest exposure categories, alongside complementary analyses harmonized to a common one-standard-deviation exposure scale. We included 12 studies in the systematic review. In the primary analyses, monobutyl phthalate (MBP)/mono-n-butyl phthalate (MnBP) (pooled odds ratio [OR] = 0.81; 95% confidence interval [CI]: 0.68–0.97) and monobenzyl phthalate (MBzP) (pooled OR = 0.76; 95% CI: 0.62–0.93) showed inverse associations with breast cancer, whereas the other metabolites included in the primary meta-analyses showed no statistically significant associations. After harmonization, the inverse association persisted for MBP/MnBP (pooled OR = 0.92; 95% CI: 0.85–0.99), and monoethyl phthalate (MEP) showed an inverse association (pooled OR = 0.87; 95% CI: 0.77–0.99), whereas MBzP was no longer statistically significant. These inverse associations should not be interpreted as protective biological effects, as they may reflect bias, residual confounding, or exposure misclassification. Overall, evidence shows no consistent association between phthalate exposure and breast cancer.