Urinary levels of proteins and metabolites in workers exposed to toluene

We measured urinary excretion of albumin and retinol-binding proteins to investigate the occurrence of early renal dysfunction in 45 paint workers exposed principally to toluene, and in the same number of unexposed control subjects matched individually for sex and age. Two biological indicators of personal toluene absorption, namely urine hippuric acid and o-cresol, were also measured in the exposed subjects. A significantly higher level and increased prevalence of elevated retinol-binding protein in the urine of exposed workers was found, whereas no significant difference in urinary albumin concentration was seen between the two groups. Urinary concentrations of retinol-binding protein was correlated (r = 0.399, P less than 0.006) with that of o-cresol, but not with hippuric acid or employment duration. The results suggest a dose-dependent early tubular effect due to toluene exposure that might be useful for monitoring individuals exposed to toluene at work.