Unmetabolized hydrocarbons in urine as biomarkers of low exposure in asphalt workers

The aim of the study was the assessment of low-level exposure to polycyclic aromatic hydrocarbons (PAHs) by biological monitoring focusing on measurement of unmetabolized PAHs in urine. Italian asphalt workers (AW, n = 100) and roadside construction workers (CW, n = 47) were investigated by measurement of unmetabolized PAHs and 1-hydroxypyrene (OH-Py) in urine spot samples collected respectively after two days of vacation (baseline), before and at the end of the monitored workshift, in the second part of the workweek. Personal exposure was also assessed by use of active samplers collecting both vapor- and particulate-phase PAHs. Median airborne levels during the workshift of 15 PAHs (both vapor and particulate phases), from naphthalene to indeno(1,2,3- cd)pyrene, ranged from below 0.03 to 426 ng/m3. Median excretion values of OH-Py in end-shift samples was 690 ng/L for AW and 378 ng/L for CW (p < 0.01). Urinary low-boiling PAHs were detected in the majority of the samples. Median levels for urinary naphthalene, phenanthrene, fluoranthene, and pyrene in end-shift samples were 117, 50, 8, and 6 ng/L in AWand 104, 19, 5, and 4 ng/L inCW, respectively. Significantly higher levels of most of the unmetabolized compounds were found in AW than in CW. Moreover, in AW samples the urinary excretion of most analytes increased during the work shift (before-shift vs. end-shift) and the workweek (baseline vs. before-shift). Urinary high-boiling PAHs were found in less than 10% of the samples. Significant correlations between airborne and urinary PAHs were observed. The results of this study show that low-boiling unmetabolized PAHs in urine may be suggested as biomarkers of low-level exposure to PAHs.