Nearly all breast milk samples tested from mothers in Seattle contained hormone-disrupting chemicals, according to new peer-reviewed research that has raised serious concerns about infant exposure to a cocktail of industrial compounds.
Widespread contamination in breast milk
The study, led by scientists at the nonprofit group Toxic Free Future, analysed 50 samples of breast milk donated by mothers in the Seattle area. It found that 92% of the samples were contaminated with at least one of the antimicrobials or plasticisers for which researchers checked. The chemicals detected included bisphenol A (BPA), bisphenol S (BPS), melamine, cyanuric acid and triclosan. The same milk samples had previously been found to contain potentially dangerous levels of PFAS “forever chemicals” and flame retardants, which are also endocrine disruptors.
BPA and BPS were present in 74% and 78% of samples respectively, while triclosan was found in 62%. Melamine, a plasticiser often used in resins and packaging, appeared in 92% of samples. The study is among the first to detect melamine alongside multiple other classes of endocrine-disrupting chemicals in breast milk, the authors said.
How these chemicals interfere with infant development
The presence of these compounds is particularly alarming because they are known to interfere with the endocrine system, which orchestrates the rapid stages of growth and development that infants and children undergo. Even at very low levels of exposure, these chemicals have been shown to cause harm. The endocrine system controls hormone signaling critical to brain development, metabolism, reproduction and immune function, and disruption during early life can have lasting consequences.
Epidemiological studies have linked BPA to impaired neurodevelopment, asthma and obesity. BPS, which is often used as a replacement for BPA, has been associated with lower weight in young children. The antimicrobial triclosan, commonly added to personal care products, was present in 62% of samples, and researchers noted that limited studies on mixtures of these chemicals have linked them to lower birth weight and size.
Although some of the compounds were found at levels below the World Health Organization’s tolerable daily intake, the authors stressed that concentrations were still at levels that previous research has indicated may cause disease. “These are the most vulnerable group when it comes to health effects – infants and children – who are undergoing rapid stages of development that are orchestrated by the endocrine system,” said Ryan Babadi, a lead author of the study and senior scientist at Toxic Free Future.
The study acknowledged limitations, including a small sample size and a participant group that was broadly more educated and higher-income than the general population. Nevertheless, the findings underscore a systemic problem, particularly because the chemicals are used so widely that even well-informed consumers cannot avoid them entirely. “You cannot shop your way out of this,” Babadi said.
Regulatory failure and calls for stronger protections
The research points to a “widespread, systemic problem” driven by the extensive use of these compounds by chemical companies and a failure by regulators to control their use, Babadi said. The endocrine disruptors are regularly added to everyday products across the economy – triclosan in personal care items, melamine and bisphenols in resins that prevent sticking, give plastic its form or provide UV protection. The same chemicals are also found in infant formula, meaning breastfeeding remains the healthiest choice for infants when possible, he added.
The results come as the Trump administration’s Environmental Protection Agency launches a multi‑pronged effort to undo limits on many toxic chemicals and carcinogens in consumer goods or water, and to weaken the regulatory process. Congress is also considering gutting the nation’s laws around toxic chemicals. “We need stronger protections on these policies, not rollbacks,” Babadi said. “That would make the exposures we see in this paper worse, and it would worsen the health of not only children but adults, workers and communities.”