Distribution of parabens and 4-HB in human blood

Human blood has been commonly and routinely analyzed to determine internal human exposure to parabens. However, data on the occurrence of parabens and their common metabolite, p-hydroxybenzoic acid (4-HB), in different human blood matrixes is still limited. In this study, 139 pairs of serum and whole blood samples were collected from Chinese adults, and then analyzed them for 5 parabens and 4-HB. Methylparaben (MeP) and propylparaben (PrP) were consistently the predominant parabens in human serum (mean 2.3 and 2.1 ng/mL, respectively) and whole blood (1.9 and 1.3 ng/mL, respectively). Mean concentrations of 4-HB in human serum and whole blood were 7.7 and 12 ng/mL, respectively. Concentrations of parabens, except benzylparaben (BzP), and 4-HB in human serum were significantly (p < 0.01) correlated with that in whole blood. Distribution pattern of parabens and 4-HB in human blood was evaluated, for the first time, based on their partitioning between human serum and whole blood (K_p). Mean K_p values of parabens, except BzP, increased with the alkyl chain length from 0.83 to 1.6. BzP (mean 1.4) had a comparable mean K_p value to PrP (mean 1.4). Among target analytes, 4-HB had the lowest mean K_p value (0.75). These data are important to select appropriate blood matrixes for conducting human exposure assessment and epidemiological studies on parabens.