Perfluorooctanoic acidPerfluorooctanesulfonic acidHuman serumHPLC-MS/MSSurrogated analyteKorean populationPERFLUOROALKYL SUBSTANCES PFASSPOLYFLUOROALKYL SUBSTANCESPERFLUORINATED COMPOUNDSHUMAN EXPOSURELONGITUDINAL ANALYSISPRENATAL EXPOSUREPREGNANT-WOMENGREAT-LAKESWATERHEALTH