Evaluation of biomarkers of occupational exposure to toluene at low levels.
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.
Kawai
Toshio
T
Osaka Occupational Health Service Center, Japan Industrial Safety and Health Association, Nishi-ku, Osaka 550-0001, Japan.
Ukai
Hirohiko
H
Inoue
Osamu
O
Maejima
Yuki
Y
Fukui
Yoshinari
Y
Ohashi
Fumiko
F
Okamoto
Satoru
S
Takada
Shiro
S
Sakurai
Haruhiko
H
Ikeda
Masayuki
M
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
D015415:Biomarkers; D014050:Toluene