Study Finds Endocrine-Disrupting Chemicals in Breast Milk and Infant Urine
Breast milk, a newborn’s first source of nutrition, is considered the gold standard for infant health. Rich in essential nutrients, antibodies, and protective compounds, this nature’s gift is crucial for early development. But what if something invisible was lurking in those first precious feedings? A new study presented at ENDO 2026, the Endocrine Society’s annual meeting in Chicago, Illinois, on Saturday (13 June), found that endocrine-disrupting chemicals (EDCs) were present in breast milk.
Endocrine Disruptors in Breast Milk and Infant Urine
The researchers found traces of these endocrine disruptors not only in breast milk but also in infant urine up to the age of six months. “Breast milk is the optimal nutritional source for any child and must be protected, as it is a vehicle of environmental contaminants. Infancy represents a critical window of exposure since effects are magnified at this age, with damage becoming evident after many years,” said Maria Elisabeth Street, MD, PhD, associate professor and director of the Division of Paediatric Endocrinology at the University of Parma and University Hospital of Parma, Parma, Italy.
Harmful Chemicals Detected in Breast Milk
The researchers used data from 336 mother–infant pairs enrolled in the LIFE-MILCH project to examine the presence of EDCs. They collected samples at various intervals, including one month, three months, and six months after birth. They measured exposure to more than 50 different chemicals, including bisphenols (BPA), polycyclic aromatic hydrocarbons, phthalates and their metabolites, parabens, polar pesticides, and pyrethroids.
What they found was striking. Traces of BPA were detected in breast milk one month after birth (51.2%), making it the most common chemical. BPA was also found six months postpartum (49.8%). It was also detected in the urine samples of nearly a third of the infants following birth, rising to 67.6% when the infants were six months old.
Another striking discovery was the presence of bisphenol S (BPS) in breast milk one month after birth (10.7%) and at six months after birth (18.3%), as well as in infant urine samples at birth (22.4%) and at six months of age (41.2%). Most polycyclic aromatic hydrocarbons were rarely detected in breast milk, but several were consistently found in urine (up to 27.7%).
Endocrine disruptors such as methylparaben (MePB) and ethylparaben (EtPB) were most commonly found at one month (51.2%; 42.3%) and six months postpartum (56.2%; 52.6%) in breast milk. The presence of these chemicals increased in urine samples over time.
The researchers also found glufosinate in breast milk one month after birth (27.4%) and three months after birth (31.9%), and in urine samples at birth (44.7%) and at six months of age (38.2%).
While most products today claim to be phthalate-free, the milk and urine samples suggested otherwise. Phthalates, including dibutyl phthalate (DBP), were found in 90.2% of breast milk samples at one month postpartum and 86.5% at six months postpartum. Levels in urine samples increased from 30.3% at birth to 79.4% at six months of age.
How These Chemicals Enter the Human Body
The researchers also examined how these endocrine-disrupting chemicals entered breast milk. Interestingly, most EDCs found in breast milk and urine samples were linked to dietary habits and products used for personal and household care. Exposure to these chemicals was linked to neurodevelopmental issues, hormonal activation at birth, and androgenisation, or the development of male reproductive characteristics. Street also emphasised that exposure to EDCs can alter growth, weight, and obesity.
