title: Metal mixtures in urban and rural populations in the US: The Multi-Ethnic Study of Atherosclerosis and the Strong Heart Study.
abstract: BACKGROUND
  Natural and anthropogenic sources of metal exposure differ for urban and rural residents. We searched to identify patterns of metal mixtures which could suggest common environmental sources and/or metabolic pathways of different urinary metals, and compared metal-mixtures in two population-based studies from urban/sub-urban and rural/town areas in the US: the Multi-Ethnic Study of Atherosclerosis (MESA) and the Strong Heart Study (SHS).
  
  
  METHODS
  We studied a random sample of 308 White, Black, Chinese-American, and Hispanic participants in MESA (2000-2002) and 277 American Indian participants in SHS (1998-2003). We used principal component analysis (PCA), cluster analysis (CA), and linear discriminant analysis (LDA) to evaluate nine urinary metals (antimony [Sb], arsenic [As], cadmium [Cd], lead [Pb], molybdenum [Mo], selenium [Se], tungsten [W], uranium [U] and zinc [Zn]). For arsenic, we used the sum of inorganic and methylated species (∑As).
  
  
  RESULTS
  All nine urinary metals were higher in SHS compared to MESA participants. PCA and CA revealed the same patterns in SHS, suggesting 4 distinct principal components (PC) or clusters (∑As-U-W, Pb-Sb, Cd-Zn, Mo-Se). In MESA, CA showed 2 large clusters (∑As-Mo-Sb-U-W, Cd-Pb-Se-Zn), while PCA showed 4 PCs (Sb-U-W, Pb-Se-Zn, Cd-Mo, ∑As). LDA indicated that ∑As, U, W, and Zn were the most discriminant variables distinguishing MESA and SHS participants.
  
  
  CONCLUSIONS
  In SHS, the ∑As-U-W cluster and PC might reflect groundwater contamination in rural areas, and the Cd-Zn cluster and PC could reflect common sources from meat products or metabolic interactions. Among the metals assayed, ∑As, U, W and Zn differed the most between MESA and SHS, possibly reflecting disproportionate exposure from drinking water and perhaps food in rural Native communities compared to urban communities around the US.
authors.affiliation: Departments of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA. Electronic address: yuanjie.p@gmail.com.
authors.forename: Yuanjie
authors.initials: Y
authors.lastname: Pang
authors.affiliation: Departments of Biostatistics, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA. Electronic address: rdpeng@jhu.edu.
authors.forename: Roger D
authors.initials: RD
authors.lastname: Peng
authors.affiliation: Departments of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA. Electronic address: mjone132@jhu.edu.
authors.forename: Miranda R
authors.initials: MR
authors.lastname: Jones
authors.affiliation: Institute of Chemistry -Analytical Chemistry, University of Graz, Graz 8010, Austria. Electronic address: kevin.francesconi@uni-graz.at.
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Francesconi
authors.affiliation: Institute of Chemistry -Analytical Chemistry, University of Graz, Graz 8010, Austria. Electronic address: walter.goessler@uni-graz.at.
authors.forename: Walter
authors.initials: W
authors.lastname: Goessler
authors.affiliation: MedStar Health Research Institute, Hyattsville, MD 20782, USA; Georgetown-Howard Universities Center for Clinical and Translational Science, Washington, DC 20057, USA. Electronic address: Barbara.V.Howard@Medstar.net.
authors.forename: Barbara V
authors.initials: BV
authors.lastname: Howard
authors.affiliation: MedStar Health Research Institute, Hyattsville, MD 20782, USA; Georgetown-Howard Universities Center for Clinical and Translational Science, Washington, DC 20057, USA. Electronic address: jason.umans@gmail.com.
authors.forename: Jason G
authors.initials: JG
authors.lastname: Umans
authors.affiliation: Missouri Breaks Industries Research, Inc., Timber Lake, SD 57656, USA. Electronic address: lbest@restel.com.
authors.forename: Lyle G
authors.initials: LG
authors.lastname: Best
authors.affiliation: Departments of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA; Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA; Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA. Electronic address: eguallar@jhu.edu.
authors.forename: Eliseo
authors.initials: E
authors.lastname: Guallar
authors.affiliation: Departments of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA; Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA; Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA. Electronic address: wpost@jhmi.edu.
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Post
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA 98195, USA. Electronic address: joelk@u.washington.edu.
authors.forename: Joel D
authors.initials: JD
authors.lastname: Kaufman
authors.affiliation: Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA. Electronic address: dvaidya@jhmi.edu.
authors.forename: Dhananjay
authors.initials: D
authors.lastname: Vaidya
authors.affiliation: Departments of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA; Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA; Department of Environmental Health Sciences, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA. Electronic address: anavasa1@jhu.edu.
authors.forename: Ana
authors.initials: A
authors.lastname: Navas-Acien
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001151:Arsenic / Q000652:urine*; D016000:Cluster Analysis; D015331:Cohort Studies; D004781:Environmental Exposure / Q000032:analysis*; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data; D008875:Middle Aged; D025341:Principal Component Analysis; D012424:Rural Population / Q000706:statistics & numerical data; D014414:Tungsten / Q000652:urine*; D014481:United States; D014501:Uranium / Q000652:urine*; D014505:Urban Population / Q000706:statistics & numerical data
chemical_list: D014501:Uranium; D001151:Arsenic; D014414:Tungsten
keywords: Biomarker; Exposure sources; Metals; Statistical methods; Urine