title: Evaluation of biomarkers of occupational exposure to toluene at low levels.
abstract: OBJECTIVE
  The purpose of the present study was to compare validity of various biomarkers of occupational exposure to toluene (Tol) at low levels. The focus was placed on the comparison of un-metabolized toluene in urine (Tol-U) and peripheral blood (Tol-B) with hippuric acid in urine (HA-U).
  
  
  METHODS
  Surveys were conducted in 16 workplaces on the second half of working weeks, with participation of male solvent workers. Urine and peripheral blood samples were collected at the end of the shifts. After exclusion of cases with dense or diluted urine samples, 473 valid sets of samples were obtained for statistical evaluation. Time-weighted average exposure (for about 8-h) were monitored by diffusive sampling for toluene and other four solvents. Blood samples were subjected to the analyses for Tol-B, whereas urine samples were analyzed for HA-U and Tol-U.
  
  
  RESULTS
  The solvent exposures were low, i.e., a grand geometric mean (GM) Tol concentration was 1.6 ppm, and the GM for the SUM in the additiveness equation was 0.12. The correlation analyses of the biomarkers in urine and blood with Tol exposure showed that Tol-U and Tol-B were more closely [correlation coefficients (r) being 0.67 and 0.60, respectively] related than HA-U (r = 0.27). Results of receiver operator characteristic analyses were in agreement with the correlation analysis results.
  
  
  CONCLUSIONS
  Taking the non-invasive nature of sampling together, Tol in the end-of-shift spot urine sample appears to be the marker of choice for biological monitoring of occupational exposure to Tol at low levels such as <2 ppm as a geometric mean.
authors.affiliation: Osaka Occupational Health Service Center, Japan Industrial Safety and Health Association, Nishi-ku, Osaka 550-0001, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kawai
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Ukai
authors.forename: Osamu
authors.initials: O
authors.lastname: Inoue
authors.forename: Yuki
authors.initials: Y
authors.lastname: Maejima
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Fukui
authors.forename: Fumiko
authors.initials: F
authors.lastname: Ohashi
authors.forename: Satoru
authors.initials: S
authors.lastname: Okamoto
authors.forename: Shiro
authors.initials: S
authors.lastname: Takada
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sakurai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ikeda
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000032:analysis*; D014050:Toluene / Q000032:analysis* / Q000097:blood / Q000652:urine; D016482:Urinalysis / Q000379:methods
chemical_list: D015415:Biomarkers; D014050:Toluene