BIOMARKERS OF EXPOSURE TO LOW CONCENTRATIONS OF BENZENE - A FIELD ASSESSMENT

Objective-To carry out a comprehensive field investigation to evaluate various conventional and recently developed biomarkers for exposure t o low concentrations of benzene. Methods-Analyses were carried out on environmental air, unmetabolised benzene in blood and urine, urinary t rans, trans-muconic acid, and three major phenolic metabolites of benz ene: phenol, catechol, and hydroquinone. Validations of these biomarke rs were performed on 131 never smokers occupationally exposed to the t ime weighted average benzene concentration of 0.25 ppm (range, 0.01 to 3.5 ppm). Results-Among the six biomarkers studied, unmetabolised ben zene in urine correlated best with environmental benzene concentration (correlation coefficient, r = 0.76), followed by benzene in blood (r = 0.64). When urinary metabolites were compared with environmental ben zene, trans, trans-muconic acid showed a close correlation (r = 0.53) followed by hydroquinone (r = 0.44), and to a lesser extent with urina ry phenol (r = 0.38). No correlation was found between catechol and en vironmental benzene concentrations. Although unmetabolised benzene in urine correlates best with benzene exposure, owing to serious technica l drawbacks, its use is limited. Among the metabolites, trans, trans-m uconic acid seems to be more reliable than other phenolic compounds. N evertheless, detailed analyses failed to show that it is specific for monitoring benzene exposures below 0.25 ppm. Conclusion-The overall re sults suggest that most of the currently available biomarkers are unab le to provide sufficient specificity for monitoring of low concentrati ons of benzene exposure. If a lower occupational exposure limit for be nzene is to be considered, the reliablity of the biomarker and the tec hnical limitations of measurements have to be carefully validated.