title: Exposure to toxic agents alters organic elemental composition in human fingernails.
abstract: OBJECTIVE
  The human fingernail plate is highly keratinized. The keratin structure is held together by disulfide bonds. The organic elements sulfur and nitrogen occur almost exclusively in amino acids of the nail plate. This study analyzed whether occupational exposure to harmful chemical agents alters the organic elemental composition in fingernails.
  
  
  METHODS
  Participants were 71 occupationally exposed workers (49 hairdressers, 22 painters) and 49 unexposed controls. Aspects of exposure were assessed by questionnaire. Nail clippings of index and little fingers were analyzed for sulfur (S), nitrogen (N), carbon (C), and hydrogen (H) contents, using an automatic elemental analyzer (Vario EL III, Elementar Analysensysteme, Hanau, Germany). C/N, N/S, and C/S ratios were calculated. Reliability of elemental measurements was tested in a subset.
  
  
  RESULTS
  Reliability analysis of elemental measurements showed a very good agreement. Both painters and hairdressers displayed in their fingernails significantly lower percentages of sulfur, but higher percentages of carbon than unexposed controls. A trend was observed in that sulfur content was lowest in those hairdressers who reported structural changes in their fingernails. As a consequence, the C/S and N/S ratios were significantly increased in both exposed groups.
  
  
  CONCLUSIONS
  The occupational use of harmful substances leads to decreased sulfur levels in the exposed persons, probably due to diminution of sulfur-rich proteins in the nails, resulting from destruction of disulfide-bonds by alkaline and acid groups. Thus, the C/S ratio seems to be a useful indicator for the amount of damage of nail protein by harmful agents.
authors.affiliation: Institute of Anthropology, Department of Biology, Johannes Gutenberg-University, 55128 Mainz, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Schumacher
authors.forename: Willi
authors.initials: W
authors.lastname: Dindorf
authors.forename: Manuela
authors.initials: M
authors.lastname: Dittmar
mesh_terms: D000328:Adult; D002244:Carbon / Q000032:analysis; D005260:Female; D006203:Hair Preparations / Q000633:toxicity*; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009262:Nails / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis; D016273:Occupational Exposure / Q000032:analysis*; D010150:Paint / Q000633:toxicity*; D012737:Sex Factors; D013455:Sulfur / Q000032:analysis
chemical_list: D006203:Hair Preparations; D013455:Sulfur; D002244:Carbon; D006859:Hydrogen; D009584:Nitrogen