No abstract

Information on placental transfer and adverse outcomes of short-chain per- and polyfluoroalkyl substance (PFASs) is limited, and factors responsible for PFAS placental transfer are still unclear. In the present study, concentrations of 21 PFASs were analyzed in 132 paired maternal and cord serum samples collected from residents in Beijing, China, and the placental transfer efficiency (PTE) of each PFAS was calculated. PTEs of short-chain perfluoroalkyl acids (PFAAs), including PFBA (146%), PFBS (97%), PFPeA (118%), and PFHxA (110%), were first reported, and a complete U-shaped trend of PTEs from C4 to C13 of perfluoroalkyl carboxylic acids (PFCAs) was obtained. Positive association between maternal weight and PTE of perfluorooctanesulfonate (PFOS) (p < 0.05) and negative association between maternal PFBA concentration and birth length (p < 0.01) were observed. Using in vitro experiments, we further determined equilibrium dissociation constants (K ds) of human serum albumin (HSA)–PFAS complexes (K d‑HP), serum proteins–PFAS complexes (K d‑SP), and liver-fatty acid binding protein (L-FABP)–PFAS complexes (K d‑LP) and found that they were all significantly correlated with PTEs of PFASs. The correlation coefficient was 0.92, 0.89, and 0.86, respectively (p < 0.01 in all three tests), suggesting that K ds of protein (serum)–PFAS complexes can play an important role in trans-placental transfer of PFASs in human and K d‑HP plays a pivotal role.

This paper reports a paleomagnetic study of Jurassic rocks from the Ordos Basin in the North China Block (NCB). A recent remagnetization and a high‐temperature and/or high‐coercivity component with dual polarities have been isolated. The Middle Jurassic pole (74°N, 233°E, A95=5°) is roughly consistent with previous results, and the Lower Jurassic pole (82°N, 286°E, A95=7°) is located between the late Triassic and Middle Jurassic poles. These results, combined with paleomagnetic results from adjacent blocks, suggest that 1) the pole for the NCB suffered an angular displacement of 47°+/− 8° between the late Triassic and Middle Jurassic, 2) the SCB underwent final accretion to the NCB in the Middle Jurassic, and 3) accretion of the NCB to Siberia was not complete until the late Jurassic and possibly even until the early Cretaceous.