This isn’t the breast news.
Breast milk is widely considered the gold standard for infant nutrition, with the Dietary Guidelines for Americans recommending it be given exclusively for the first six months of life when possible.
But scientists are now sounding the alarm after two new studies found a mix of potentially harmful chemicals in samples from hundreds of mothers — raising concerns they could interfere with a baby’s hormones during a critical stage of development.
In the first study, a team of Italian researchers analyzed breast milk and urine from 336 mothers and their babies, collected at one month, three months and six months after birth.
They tested for more than 50 potentially harmful substances and found many contained traces of endocrine-disrupting chemicals, or EDCs, which can interfere with how hormones work in the body.
Bisphenol A, or BPA, a chemical used in plastic food containers, receipt paper and other everyday products, was detected in 51.2% of breast milk samples one month after birth, dipping slightly to 49.8% at six months postpartum.
Among babies, about one in three had BPA in their urine shortly after birth, increasing to nearly two-thirds by the time they were six months old.
A similar chemical called Bisphenol S, often used as a BPA replacement in plastics, was also found in both mothers and babies, with levels rising over time.
Chemicals linked to vehicle exhaust and fuel burning, known as polycyclic aromatic hydrocarbons, were rarely found in milk but were consistently detected in babies’ urine.
Parabens, which are preservatives used in shampoos, lotions and cosmetics, were also commonly detected, with levels in infants increasing as they aged.
Glufosinate, a weedkiller used in agriculture, was detected in both mothers and babies at multiple points throughout the study.
And phthalates, used to make plastics softer and more flexible, were found in more than 90% of breast milk samples taken one month after birth and remained common at six months, with levels in babies’ urine rising sharply over time.
Studies have linked these chemicals to possible health problems in infants, including hormone disruption, changes in growth and weight, and potential effects on brain development and long-term metabolism.
“Breast milk is the optimal nutritional source for any child and must be protected as it is a vehicle of environmental contaminants,” Dr. Maria Elisabeth Street, study author and director of the Division of Pediatric Endocrinology at the University of Parma in Italy, said in a press release.
“Infancy represents a critical window of exposure since effects are magnified at this age with damage becoming evident after many years.”
In the second study, researchers in Seattle examined breast milk from 50 new mothers and found that about 92% contained at least one endocrine-disrupting chemical.
Those same samples had already been shown to contain PFAS — known as “forever chemicals” because they do not break down easily in the body or environment — as well as flame retardants, both of which are also known to interfere with hormones.
While some of the chemicals were below World Health Organization safety thresholds, the study authors noted they were still at levels that past research has linked to possible negative health effects.
“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,” Dr. Ryan Babadi, science director for Toxic-Free Future, which contributed to the research, said in a statement.
“These exposures highlight the need for stronger safeguards so families are not put in harm’s way simply by feeding their babies.”
Each year, more than 3.5 million women give birth in the US, and research shows about 84% at least begin breastfeeding.
The authors of both studies stressed that their findings aren’t meant to discourage the practice, which provides ideal nutrition for infants and can help protect both mother and baby from a range of short- and long-term illnesses.
Instead, they said their research highlights a broader need to reduce environmental contamination and limit exposure to these potentially toxic substances.
“The presence of these chemicals in breast milk shows we need to do more to protect public health,” Babadi said.