Endocrine-disrupting chemicals in breast milk and early life exposure for infants in the United States

Abstract

Breastfeeding can be a source of exposure to endocrine-disrupting chemicals (EDCs) for infants, but limited information exists on exposure to commonly used chemicals such as melamine and bisphenols in nursing infants in the US. We aimed to measure a suite of EDCs in breast milk and evaluate exposure of nursing infants to these chemicals. We analyzed EDCs in breast milk samples collected from 50 women in Seattle, Washington during 2019, including melamine, cyanuric acid, ammeline, ammelide, bisphenol A (BPA), 4-hydroxyphenyl sulfone (BPS), 4,4′-methylenediphenol, (4,4′-hexafluoroisopropylidene) diphenol, fluorene-9-bisphenol, and triclosan. We examined associations of infant age at sample collection and maternal characteristics with log10-transformed chemical concentrations using linear regression. Estimated daily intake (EDI) of each chemical through breast milk was calculated for infants 0–12 months old using our sample median chemical concentrations. We frequently detected (62–92%) melamine, cyanuric acid, BPA, BPS, and triclosan in breast milk. Median concentrations were 0.48 ng/mL melamine, 0.59 ng/mL cyanuric acid, 0.311 ng/mL BPA, 0.012 ng/mL BPS, and 0.072 ng/mL triclosan. Older infant age (>6 versus <6 months) was associated with lower melamine concentrations (-0.41, 95% CI: −0.80, −0.01). Maternal obesity was associated with higher BPA (0.68, 95% CI: 0.14, 1.23) and maternal overweight with higher triclosan (0.43, 95% CI: 0.06, 0.80). Other associations with participant characteristics were suggestive but not statistically significant. EDIs for infants in the average exposure scenario ranged by infant age from 40.3 to 72.8 ng/kg-bodyweight/day for melamine and 86.5–156 ng/kg-bodyweight/day for BPA. We frequently detected melamine, cyanuric acid, BPA, BPS, and triclosan in breast milk. EDIs through breastfeeding were generally higher than for other exposure pathways (e.g., dermal uptake, dust ingestion or inhalation), and more work is needed to understand potential health effects of chronic infant exposures to even low levels of these ubiquitous chemicals through breast milk. This study adds to the limited research to date on endocrine-disrupting chemicals in breast milk, exposure among nursing infants in the US, and differences by infant and maternal characteristics, to further inform cumulative exposure assessment in infants and regulatory thresholds. Melamine, cyanuric acid, BPA, BPS, and triclosan were detected with high frequency in breast milk samples in our study, and our study suggests that breast milk is an important exposure pathway for these chemicals among nursing infants. Given the importance of breastfeeding for infant health, our study highlights the need to investigate potential health effects of these chronic exposures.