Hormone-Disrupting Chemicals Found in Up to 92% of US Breast Milk Samples — Study Confirms
A new peer-reviewed study has detected endocrine-disrupting chemicals — compounds known to interfere with the body's hormone systems — in the majority of US breast milk samples tested, with detection rates reaching as high as 92%.
The research, conducted by Toxic-Free Future in collaboration with Seattle Children's, analysed breast milk samples collected from 50 women in Seattle, Washington, screening for a panel of chemicals including bisphenols, melamine and related compounds, and triclosan. According to Toxic-Free Future, these chemicals were detected in 62% to 92% of samples.
"These findings show that infants and their mothers are being exposed to hormone-disrupting chemicals used in everyday products, including plastics, during critical stages of development," said one of the study's researchers, per Toxic-Free Future.
What Was Found — and at What Levels
The chemical breakdown reveals a pattern researchers describe as "regrettable substitution."
Bisphenol A (BPA) — long flagged as a hormone disruptor and the subject of years of regulatory action — was found in 74% of breast milk samples. But its replacement, bisphenol S (BPS), appeared in 78% of samples, a higher detection rate than the chemical it was meant to replace. Triclosan, an antibacterial agent used in plastics and personal care products, was detected in 62% of samples.
The study, published in the Journal of Exposure Science & Environmental Epidemiology, also frequently detected melamine, cyanuric acid, and several other bisphenol-class compounds. Researchers calculated estimated daily intake (EDI) for infants aged 0–12 months based on median chemical concentrations in the samples — and found that breastfeeding represented a higher EDC exposure pathway than dermal contact or dust ingestion, the two other routes typically studied.
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A Second Study Confirms the Pattern Globally
The Seattle findings are not an isolated result.
Days earlier, at ENDO 2026 — the Endocrine Society's annual conference held in Chicago — a separate study presented similar findings on a different scale. Researchers detected endocrine-disrupting chemicals in both the breast milk of nursing mothers and the urine of their infants from birth up to six months of age, according to the Endocrine Society.
"Breast milk is the optimal nutritional source for any child and must be protected as it is a vehicle of environmental contaminants," said Dr. Maria Elisabeth Street, associate professor and Director of the Division of Pediatric Endocrinology at the University of Parma and University Hospital of Parma, presenting the findings.
A broader global review of 71 English-language studies, published in *Current Environmental Health Reports* in late 2025, documented measurable levels of EDCs — including bisphenols, perfluorinated chemicals, pesticides, flame retardants, and plasticizers — in breast milk samples worldwide, per US Right to Know. The review's principal investigator, Dr. Katherine E., noted that "nursing infants can be exposed to mixtures of EDCs via breast milk, which may carry risks for early-life development, particularly for neurodevelopment and thyroid function."
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Why Experts Still Recommend Breastfeeding
The finding poses an obvious question for new parents — and researchers were direct in addressing it.
The World Health Organization continues to advise exclusive breastfeeding for the first six months of life, citing protection from infections and lifelong benefits including lower risks of learning disabilities, diabetes, obesity, and hypertension. Every source covering this research was emphatic that breastfeeding remains the recommended option despite the EDC findings — the benefits of breast milk's nutritional and immunological properties are understood to substantially outweigh the risks from chemical contamination at the levels detected.
The actionable message from researchers is not about breastfeeding decisions — it is about reducing the chemical load mothers are exposed to in the first place. According to Toxic-Free Future, the research has already led to collaborations with manufacturers and regulatory stakeholders in Italy, resulting in agreements to monitor, reduce, and potentially reformulate products contributing to the chemical burden found in breast milk.
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The Regulatory Response — and What's Different in Washington State
One US state has already moved on this issue, and the timing is notable.
Washington state's Safer Products for Washington law — described by Toxic-Free Future as the strongest law in the nation for regulating EDCs and other toxic chemicals in products, plastics, and packaging — banned all bisphenols in beverage can linings and thermal paper, including receipts, with that ban taking effect in January 2026.
"Washington state has led the way on safer chemicals, but the presence of these chemicals in breast milk shows we need to do more to protect public health," said Dr. Babadi, per Toxic-Free Future. The state is reportedly pursuing further regulatory action on EDCs in the coming year.
The Seattle study's findings arrive at a moment when, according to researchers, industry groups are simultaneously pushing to weaken the federal Toxic Substances Control Act (TSCA) — the primary federal law governing chemical regulation in consumer products. The contrast between state-level action accelerating in Washington and federal-level pressure to loosen restrictions illustrates the patchwork regulatory environment new parents are navigating.
Key Takeaways
- A Toxic-Free Future / Seattle Children's study found endocrine-disrupting chemicals in 62-92% of breast milk samples from 50 Seattle mothers.
- BPA detected in 74% of samples; its replacement BPS detected in 78% — a higher rate than the chemical it replaced.
- Triclosan detected in 62% of samples; breastfeeding showed higher EDC exposure than dermal or dust pathways.
- A separate ENDO 2026 study found EDCs in both breast milk and infant urine up to 6 months of age.
- Researchers and WHO guidance both affirm: breastfeeding remains recommended despite the findings.
- Washington state's bisphenol ban in can linings and receipts took effect January 2026 — among the strongest state-level EDC laws in the US.
Sources
- Toxic-Free Future — New study finds endocrine-disrupting plastic chemicals in breast milk
- Journal of Exposure Science & Environmental Epidemiology — Endocrine-disrupting chemicals in breast milk and early life exposure for infants in the United States
- Endocrine Society — EDCs found in breast milk and infant urine up to age 6 months
- US Right to Know — Hormone-disrupting chemicals contaminate breast milk, global review shows
- Breast Cancer Prevention Partners — New study finds endocrine-disrupting plastic chemicals in breast milk products
