title: Changes in urinary arsenic methylation profiles in a 15-year interval after cessation of arsenic ingestion in southwest Taiwan.
abstract: BACKGROUND
  Inorganic arsenic (iAs) is carcinogenic to humans. Methylated metabolites of arsenic (As) found in the urine could serve as potential tools for screening and early detection of cancer in populations exposed to As. Relatively little information is available regarding changes in As methylation profiles after cessation of As exposure.
  
  
  OBJECTIVE
  We examined the changes in urinary arsenic (uAs) species profiles over 15 years in a cancer-free population that has ceased heavy and prolonged ingestion of As.
  
  
  METHODS
  In 1989, a cohort study was carried out with 1,081 adults who resided in three villages in southwestern Taiwan where arseniasis was hyperendemic. After 15 years of follow-up, a subgroup of 205 cancer-free participants had completed all interviews and had uAs methylation data available. We used this group in our statistical analysis. Arsenic species were measured by high-performance liquid chromatography-hydride generation-atomic absorption spectrometry.
  
  
  RESULTS
  We compared the initial analyses from 1989 with those performed 15 years later and found that the average differences for the proportion of urinary iAs, monomethylarsonic acid (MMA(V)), and dimethylarsinic acid (DMA(V)) were -4.90%, -6.80%, and 11.69%, respectively. The elderly and those residents with longer periods of consuming high-As artesian well water exhibited greater changes (decreases) in %MMA(V).
  
  
  CONCLUSIONS
  The As methylation profiles indicate increased efficiency in As metabolism in residents after cessation of long-term exposure to high-level As. Moreover, the decreased %MMA(V) was more pronounced in the elderly cancer-free subcohort subjects.
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine Taipei Medical University, Taipei, Taiwan.
authors.forename: Yung-Kai
authors.initials: YK
authors.lastname: Huang
authors.forename: Ya-Li
authors.initials: YL
authors.lastname: Huang
authors.forename: Yu-Mei
authors.initials: YM
authors.lastname: Hsueh
authors.forename: Jimmy Tse-Jen
authors.initials: JT
authors.lastname: Wang
authors.forename: Mo-Hsiung
authors.initials: MH
authors.lastname: Yang
authors.forename: Chien-Jen
authors.initials: CJ
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D001151:Arsenic / Q000378:metabolism*; D001152:Arsenicals / Q000652:urine*; D002101:Cacodylic Acid / Q000652:urine*; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D013624:Taiwan; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D014881:Water Supply / Q000032:analysis*
chemical_list: D001152:Arsenicals; D014874:Water Pollutants, Chemical; D002101:Cacodylic Acid; C020300:monomethylarsonic acid; D001151:Arsenic