title: In vivo monitoring of epidermal absorption of hazardous substances by confocal Raman micro-spectroscopy.
abstract: BACKGROUND
  Presently, percutaneous absorption of potentially hazardous chemicals in humans can only be assessed in animal experiments, in vitro, or predicted mathematically. Our aim was to demonstrate the proof-of-principle of a novel quantitative in vivo assay for percutaneous absorption: confocal Raman micro-spectroscopy (CRS). The advantages and limitations of CRS for health risk assessments are discussed.
  
  
  METHODS
  2-butoxyethanol, toluene, and pyrene were applied in pure form, diluted in water, or in ethanol on the skin of three healthy volunteers. CRS measurements were done following application for 15 min and 3 hours. The concentrations of the three substances as a function of distance to the skin surface were calculated and further analyzed with regard to mass transport into the stratum corneum (μg/cm(2)) and the flux through the stratum corneum (μg/cm(2)h). The results were compared with the available data from literature.
  
  
  RESULTS
  Considering the preliminary nature of these data, good accordance with data from the literature was observed. In addition, we observed that 2-butoxyethanol penetrates markedly faster when dissolved in water as compared to ethanol. This observation is also in agreement with previous results.
  
  
  CONCLUSIONS
  CRS has the potential to provide fast, accurate and reliable results for advanced studies of in vivo percutaneous absorption kinetics of hazardous substances in human skin. This will require further research with other substances and under differing conditions.
authors.affiliation: Institute for Prevention and Occupational Medicine of the German Social Accident Insurance-Institute of the Ruhr-University Bochum (IPA), Bochum, Germany. broding@ipa.ruhr-uni-bochum.de
authors.forename: Horst Christoph
authors.initials: HC
authors.lastname: Broding
authors.forename: André
authors.initials: A
authors.lastname: van der Pol
authors.forename: Johanna
authors.initials: J
authors.lastname: de Sterke
authors.forename: Christian
authors.initials: C
authors.lastname: Monsé
authors.forename: Manigé
authors.initials: M
authors.lastname: Fartasch
authors.forename: Thomas
authors.initials: T
authors.lastname: Brüning
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D005026:Ethylene Glycols / Q000493:pharmacokinetics*; D005260:Female; D015386:Hazardous Substances / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D016273:Occupational Exposure; D011721:Pyrenes / Q000493:pharmacokinetics*; D012869:Skin Absorption / Q000502:physiology*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014050:Toluene / Q000493:pharmacokinetics*
chemical_list: D005026:Ethylene Glycols; D015386:Hazardous Substances; D011721:Pyrenes; D014050:Toluene; C030984:pyrene; C017096:n-butoxyethanol