title: Urine arsenic concentrations and species excretion patterns in American Indian communities over a 10-year period: the Strong Heart Study.
abstract: BACKGROUND
  Arsenic exposure in drinking water disproportionately affects small communities in some U.S. regions, including American Indian communities. In U.S. adults with no seafood intake, median total urine arsenic is 3.4 microg/L.
  
  
  OBJECTIVE
  We evaluated arsenic exposure and excretion patterns using urine samples collected over 10 years in a random sample of American Indians from Arizona, Oklahoma, and North and South Dakota who participated in a cohort study from 1989 to 1999.
  
  
  METHODS
  We measured total urine arsenic and arsenic species [inorganic arsenic (arsenite and arsenate), methylarsonate (MA), dimethylarsinate (DMA), and arsenobetaine] concentrations in 60 participants (three urine samples each, for a total of 180 urine samples) using inductively coupled plasma/mass spectrometry (ICPMS) and high-performance liquid chromatography/ICPMS, respectively.
  
  
  RESULTS
  Median (10th, 90th percentiles) urine concentration for the sum of inorganic arsenic, MA, and DMA at baseline was 7.2 (3.1, 16.9) microg/g creatinine; the median was higher in Arizona (12.5 microg/g), intermediate in the Dakotas (9.1 microg/g), and lower in Oklahoma (4.4 microg/g). The mean percentage distribution of arsenic species over the sum of inorganic and methylated species was 10.6% for inorganic arsenic, 18.4% for MA, and 70.9% for DMA. The intraclass correlation coefficient for three repeated arsenic measurements over a 10-year period was 0.80 for the sum of inorganic and methylated species and 0.64, 0.80, and 0.77 for percent inorganic arsenic, percent MA, and percent DMA, respectively.
  
  
  CONCLUSIONS
  This study found low to moderate inorganic arsenic exposure and confirmed long-term constancy in arsenic exposure and urine excretion patterns in American Indians from three U.S. regions over a 10-year period. Our findings support the feasibility of analyzing arsenic species in large population-based studies with stored urine samples.
authors.affiliation: Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA. anavas@jhsph.edu
authors.forename: Ana
authors.initials: A
authors.lastname: Navas-Acien
authors.forename: Jason G
authors.initials: JG
authors.lastname: Umans
authors.forename: Barbara V
authors.initials: BV
authors.lastname: Howard
authors.forename: Walter
authors.initials: W
authors.lastname: Goessler
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Francesconi
authors.forename: Ciprian M
authors.initials: CM
authors.lastname: Crainiceanu
authors.forename: Ellen K
authors.initials: EK
authors.lastname: Silbergeld
authors.forename: Eliseo
authors.initials: E
authors.lastname: Guallar
mesh_terms: D000368:Aged; D001151:Arsenic / Q000652:urine*; D015331:Cohort Studies; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007198:Indians, North American; D008297:Male; D008875:Middle Aged; D014481:United States
chemical_list: D001151:Arsenic