Breast milk samples from mothers in Seattle contain alarming levels of dangerous hormone-disrupting chemicals, including BPA, BPS, melamine, cyanuric acid, and triclosan, new peer-reviewed research has found.

The chemicals present a serious risk to infants because they likely interfere with hormones that are critical to newborns’ proper development, and have been found to be harmful at very low levels of exposure. About 92% of 50 samples were contaminated with at least one of the anti-microbials or plasticizers for which researchers checked.

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.

The cocktail of endocrine-disrupting chemicals is “concerning for a number of reasons”, said Ryan Babadi, a lead author of the peer-reviewed study, and senior scientist with the Toxic Free Future nonprofit.

“This pertains to 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,” Babadi said.

Previous research has shown the individual chemicals in mothers, but the new study is among the first to detect melamine, along with multiple other classes of endocrine-disrupting chemicals, in breast milk.

Babadi emphasized that breastfeeding remains the healthiest choice for infants when possible, because it is the most nutritious and generally the safest option. Many of the same chemicals are also found in formulas. However, Babadi added that the study’s results underscore a “widespread, systemic problem” because chemical companies are so widely using the compounds, and regulators are failing to rein in their use.

The endocrine disruptors are regularly added to everyday products across the economy to serve a number of purposes. The anti-microbial triclosan is frequently included in some personal care products. The plasticizers melamine, BPA and BPS are used as resins that prevent products from sticking to packaging, to help give plastic its form, or to provide UV protection, among other purposes.

The study found BPA and BPS in 74% and 78% of samples, respectively. The chemicals have been found in epidemiological studies to have a wide range of developmental and reproductive harms, and BPS is linked to lower weight in young children. BPA is associated with impaired neurodevelopment, asthma, and obesity.

Researchers also found triclosan in 62% of samples, and melamine in 92%. While there is a dearth of research on the health impacts of exposure to mixtures of endocrine-disrupting chemicals, the limited studies have linked it to lower birth weight and size.

The study’s authors note a limitation in its small sample size. It also included mothers who are broadly more educated and higher-income. Some of the compounds were found at levels below the World Health Organization’s tolerable daily intake level, the study noted, but still at levels that previous research has shown may cause disease.

While taking steps like not buying plastic can help mothers avoid the chemicals, the compounds are so ubiquitous in consumer goods that people “cannot shop their way out of this,” Babadi said.

The results come as the Trump EPA launches a multi-pronged attack on chemical regulations. It has moved to undo limits on many toxic chemicals and carcinogens in consumer goods or water. It has also attempted to weaken the regulatory process, while Congress is considering gutting the nation’s laws around toxic chemicals.

The study’s results show “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,” Babadi added.