Chemical exposure identified and quantitated in a cohort of extremely-premature infants (n=21) and breast milk samples obtained from a breastfeeding mother during the first 211 days of life (n=86). The number of identifications in each independent study are listed, as is the lowest (Min.) and highest (Max.) level of contamination. If the least contaminated sample was below the respective limit of quantitation (LOQ), it is indicated by <'LOQ'. Interestingly, from the 27 identified chemicals, 22 originate from synthetic products and 12 thereof were detected in all the analyzed premature infant plasma samples. Of the detected analytes, those with the highest frequency included multiple plasticizers, industrial chemicals, parabens, PFOA and PFOS. Figure shows a selection of the compounds that were identified and highlights the vast concentration range that is observed for some toxicants. Comparison of these concentrations with adult control samples revealed that the contamination of the infant samples with certain chemicals was substantially higher in many subjects. For example, 11 ng mL -1 BPA, 12 ng mL -1 PFOA, 17 ng mL -1 2-naphthol, 9.4 ng mL -1 4-tert-octylphenol, 0.13 ng mL -1 ethylparaben, 15 ng mL -1 methylparaben, and 2.9 ng mL propylparaben were detected in one infant. These values are all higher than the concentrations determined for both adult controls. Clearly, the adults were not in contact with the same potential intensive care unit (ICU)-related exposure sources (see Discussion) as the neonate cohort. However, it is also known that infants have a reduced drug detoxification capability . Consequently, with a lower proportion of conjugated species there might be a higher level of more potent xenobiotics in most of the participants in the cohort. Violin plots depict the distribution of detected concentrations of compounds in premature infant plasma samples (n=21). Vertical bars inside the plot indicate the first quartile, the median and the third quartile. Analytes that were identified below the respective limit of quantitation (LOQ) were set to half the LOQ in this plot. Chemicals marked with (*) were only detected below the LOQ, thus no quantitative distribution is given and only a filled circle representing half the LOQ is displayed. Chemicals marked with ( + ) were quantitated using solvent calibration because the pooled serum intended for matrix-matched calibration was significantly contaminated.