Current breast milk PFAS levels in the US and Canada: After all this time why don’t we know more?
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Background. Despite twenty years of biomonitoring studies of per- and polyfluoroalkyl substances (PFAS) in both serum and urine, we have an extremely limited understanding of PFAS concentrations in breast milk of women from the US and Canada. The lack of robust information on PFAS concentrations in breast milk and the implications for both the breastfed infants and their families were brought to the forefront by communities impacted by PFAS contamination.
Objectives. To: 1) document published PFAS breast milk concentrations in the US and Canada; 2) estimate breast milk PFAS levels from maternal serum concentrations in national surveys and communities impacted by PFAS; and 3) compare measured/estimated milk PFAS concentrations to screening values.
Methods. We identified three studies reporting breast milk concentrations in the US and Canada. To estimate breast milk PFAS concentrations, we multiplied publicly available serum concentrations (geometric mean and 95th percentile serum PFAS concentrations from two national surveys and six communities impacted by PFAS) by milk:serum partitioning ratios for four PFAS: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA) reported in the literature. Measured and estimated breast milk concentrations were compared to children’s drinking water screening values (Child Environmental Media Evaluation Guides (EMEGs)) developed by the Agency for Toxic Substances and Disease Registry (ATSDR).
Discussion. Geometric means of estimated breast milk concentrations ranged over approximately two orders of magnitude for the different surveys/communities. All geometric mean and mean estimated/measured breast milk PFOA and PFOS concentrations exceeded the Child EMEGs, sometimes by over two orders of magnitude. For PFHxS and PFNA, most measured breast milk levels were below the Child EMEGs, but for certain communities the estimated geometric mean milk concentrations were close to - or exceeded - them. Exceeding a Child EMEG does not necessarily mean that adverse public health effects will occur, but it indicates that the situation should be further evaluated. As breast milk may be the only source of hydration for the first months of life for many infants, a better understanding of environmental chemical transfer to - and concentrations in - an exceptional source of infant nutrition is critically important.