Current breast milk PFAS levels in the US and Canada: After all this time why don’t we know more?@
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Despite twenty years of biomonitoring studies of per- and polyfluoroalkyl substances (PFAS), we have a limited understanding of concentrations in breast milk from the US and Canada. The lack of information on PFAS levels in breast milk and the implications for breastfed infants and families were brought to the forefront by communities impacted by PFAS. In this study, we: 1) review published PFAS breast milk concentrations in the US and Canada; 2) estimate breast milk PFAS levels from serum concentrations in national surveys and communities impacted by PFAS; and 3) compare measured/estimated milk PFAS concentrations to screening values.
We identified three studies reporting breast milk concentrations in the US and Canada. To estimate breast milk PFAS concentrations, we multiplied publicly available geometric mean (GM) and 95th percentile serum PFAS concentrations from two national surveys (only women) and six communities impacted by PFAS (men and women) by milk:serum partitioning ratios for four PFAS: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA). Milk:serum ratios were identified from four previous studies with sample sizes ranging from 12 – 100 paired milk and serum samples. Breast milk concentrations were compared to Child Environmental Media Evaluation Guides (EMEGs) developed by the Agency for Toxic Substances and Disease Registry (ATSDR) for drinking water.
All measured breast milk concentrations of PFOA and PFOS exceeded the Child EMEGs, while most measured PFNA and PFHxS concentrations in breast milk were below the Child EMEGs. All estimated GM and mean breast milk PFOA and PFOS concentrations exceeded the Child EMEGs. For two of six communities, the estimated GM concentrations of PFHxS and PFNA were close to – or exceeded – the Child EMEGs. Exceeding a Child EMEG does not necessarily mean that adverse health effects will occur but indicates that further evaluation is needed. Milk concentrations may be overestimated because the serum data is not limited to lactating women. This analysis is limited by the paucity of adequate data to fully characterize partitioning of PFAS into breastmilk.