Biological monitoring of controlled toluene exposure.
OBJECTIVE
Widespread exposure to toluene occurs in the printing, painting, automotive, shoemaking, and speaker-manufacturing industries. The relationship between air concentrations and the absorbed dose is confounded by dermal exposure, personal protective devices, movement throughout the workplace, and interindividual differences in toluene uptake and elimination.


METHODS
To determine the best biological indicator of exposure we examined the blood and alveolar breath concentrations of toluene as well as the urinary excretion rates of hippuric acid and of o-, m-, and p-cresols from 33 controlled human inhalation exposures to 50 ppm for 2 h.


RESULTS
Among the metabolites, o-cresol was least influenced by background contributions, whereas the p-cresol and hippuric acid rates were obscured by endogenous and dietary sources. Toluene levels in alveolar breath proved to be the most accurate and noninvasive indicator of the absorbed dose. A physiologic model described blood and breath data using four measured anthropometric parameters and the fit values of extrahepatic metabolism and adipose-tissue blood flow.


CONCLUSIONS
After breathing rate and extrahepatic metabolism had been set to conservative (protective) values (the 97.5th and 2.5th percentiles, respectively) the model predicted that pre-final-shift breath levels of < or =10 micromol/m3 and post-final-shift levels of < or =150 micromol/m3 corresponded to average workplace exposure levels of < or =50 ppm toluene. Alternately, we used the distributions and covariances of the measured and fit model parameters to yield conservative pre-final-shift levels of < or =7.3 micromol/m3 and post-final-shift breath levels of < or =120 micromol/m3 that were reflective of workplace exposure levels of < or =50 ppm toluene.
Pierce
C H
CH
Department of Environmental Health, University of Washington, Seattle 98195, USA. crispo@u.washington.edu
Dills
R L
RL
Morgan
M S
MS
Vicini
P
P
Kalman
D A
DA
D000328:Adult; D000395:Air Pollutants, Occupational / Q000032:analysis* / Q000097:blood* / Q000378:metabolism; D000704:Analysis of Variance; D000886:Anthropometry; D001944:Breath Tests / Q000379:methods*; D015986:Confounding Factors, Epidemiologic; D003408:Cresols / Q000652:urine; D004784:Environmental Monitoring / Q000379:methods* / Q000592:standards; D006626:Hippurates / Q000652:urine; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015203:Reproducibility of Results; D012134:Respiratory Protective Devices; D012869:Skin Absorption; D011795:Surveys and Questionnaires; D014050:Toluene / Q000032:analysis* / Q000097:blood* / Q000378:metabolism
D000395:Air Pollutants, Occupational; D003408:Cresols; D006626:Hippurates; D014050:Toluene; C030514:hippuric acid