title: Longitudinal measures of perfluoroalkyl substances (PFAS) in serum of Gullah African Americans in South Carolina: 2003-2013.
abstract: BACKGROUND
  Charleston Harbor has elevated concentrations of PFAS in dolphins, but local human exposure data are limited.
  
  
  OBJECTIVE
  We sought to describe PFAS serum concentrations' temporal trends among Gullah African American residents of coastal South Carolina.
  
  
  METHODS
  Longitudinal measures of PFAS in blood serum from a Gullah clinical sample, without lupus, were examined using spaghetti plots and visit-to-visit change scores (e.g., differences in concentrations between visits) among the 68 participants with repeated measures available. We also modeled population-level trends among the 71 participants with any data using proportionate percentile models, accounting for clustering through robust standard errors. In a post-hoc analysis we examined heterogeneity of temporal trends by age through mixed-effects models for the log-transformed PFAS compounds.
  
  
  RESULTS
  Population concentrations of PFOS dropped approximately 9 (95% CI: 8, 10) percent each year over 2003-2013. This was concordant with individual PFOS trajectories (median PFOS change score -21.7 ng/g wet weight, interquartile range of PFOS change scores: -32.8, -14.9) and reports for other populations over this time period. Several other compounds including PFOA, PFHxS, and PFuNDA also showed a population-level decrease. However, examination of individual trajectories suggested substantial heterogeneity. Post-hoc analyses indicated that PFAS trajectories were heterogeneous by age.
  
  
  CONCLUSIONS
  Many PFAS compounds are decreasing in a sample of Gullah African Americans from coastal South Carolina. There may be age differences in the elimination kinetics of PFASs. The possible role of age as a modifier of PFAS serum trends merits further research.
authors.affiliation: Department of Preventive Medicine, Division of Biostatistics, University of Southern California, Los Angeles, CA, USA. Electronic address: mgribble@usc.edu.
authors.forename: Matthew O
authors.initials: MO
authors.lastname: Gribble
authors.affiliation: Program in Public Health and Department of Statistics; University of California, Irvine, Irvine, CA, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Bartell
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, NY, USA; Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Albany, NY, USA.
authors.forename: Kurunthachalam
authors.initials: K
authors.lastname: Kannan
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, NY, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wu
authors.affiliation: National Oceanic and Atmospheric Administration, National Ocean Service, Center for Coastal Environmental Health & Biomolecular Research, Charleston, SC, USA.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Fair
authors.affiliation: Department of Medicine, Division of Rheumatology, Medical University of South Carolina; Charleston, SC, USA.
authors.forename: Diane L
authors.initials: DL
authors.lastname: Kamen
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American; D000368:Aged; D000375:Aging / Q000097:blood; D017738:Alkanesulfonic Acids / Q000097:blood*; D002648:Child; D002851:Chromatography, High Pressure Liquid; D004781:Environmental Exposure / Q000032:analysis* / Q000706:statistics & numerical data; D004785:Environmental Pollutants / Q000097:blood*; D005260:Female; D005466:Fluorocarbons / Q000097:blood*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D013022:South Carolina; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D017738:Alkanesulfonic Acids; D004785:Environmental Pollutants; D005466:Fluorocarbons
keywords: Biomonitoring; Contaminant trends; Gullah; PFAS; PFOA; PFOS
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