title: Assessment of the genotoxicity of 1,2-dichloropropane and dichloromethane after individual and co-exposure by inhalation in mice.
abstract: OBJECTIVE
  Occurrence of cholangiocarcinoma was recently reported at a high incidence rate among the employees working for an offset printing company in Osaka, Japan. 1,2-Dichloropropane (1,2-DCP) and dichloromethane (DCM) are suspected to be the causes of the cancer, as they had been used as ink cleaners in large amounts. However, it is not clear whether these chlorinated organic solvents played a role in the occurrence of cholangiocarcinoma or why the incidence rate is so high among the workers in this industry. To provide possible evidence for this severe occupational problem, we investigated the genotoxic effects of 1,2-DCP and DCM.
  
  
  METHODS
  Male B6C3F1 and gpt Delta C57BL/6J mice were exposed by inhalation to the individual solvents or both solvents at multiple concentrations including the levels that were possibly present in the workplaces. The genotoxicity was analyzed by Pig-a gene mutation and micronuclei assays in peripheral blood and gpt mutation and comet assays in the livers of mice after repeated inhalation of 1,2-DCP or/and DCM.
  
  
  RESULTS
  The Pig-a mutant frequencies and micronuclei incidences were not significantly increased by exposure of either 1,2-DCP or/and DCM at any concentration, suggesting there was no genotoxic potential in bone marrow for both solvents. In the liver, DNA damage, as measured by the comet assay, was dose dependently increased by 1,2-DCP but not by DCM. The gpt mutant frequency was 2.6-fold that of the controls in the co-exposure group.
  
  
  CONCLUSIONS
  These results indicate that 1,2-DCP showed stronger genotoxicity in the liver and that the genotoxic effects were greatly enhanced by simultaneous exposure to DCM.
authors.affiliation: Division of Health Effects Research, National Institute of Occupational Safety and Health.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Suzuki
authors.forename: Yukie
authors.initials: Y
authors.lastname: Yanagiba
authors.forename: Megumi
authors.initials: M
authors.lastname: Suda
authors.forename: Rui-Sheng
authors.initials: RS
authors.lastname: Wang
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000187:drug effects; D004249:DNA Damage; D019570:Inhalation Exposure; D008099:Liver / Q000187:drug effects; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008752:Methylene Chloride / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009153:Mutagens / Q000633:toxicity*; D011407:Propane / Q000031:analogs & derivatives* / Q000633:toxicity; D012997:Solvents / Q000633:toxicity*
chemical_list: D008565:Membrane Proteins; D009153:Mutagens; D012997:Solvents; C080086:phosphatidylinositol glycan-class A protein; D008752:Methylene Chloride; C004765:propylene dichloride; D011407:Propane