Occupational Exposures through Inhalation and Dermal Contact among Hot Asphalt Roofers in Denver

Abstract

Construction work has been repeatedly linked to occupational cancers and roofers are among the most vulnerable group in this industry. Work with hot asphalt has been the main concern, but co-exposure to coal tar is viewed as a significant confounder. This study fills an important research gap by quantifying exposures to polycyclic aromatic hydrocarbons (PAH) through inhalation and dermal routes. Twenty roofers have been recruited from a construction site at the Air Force Academy in Colorado. Information on work and task related factors and use of personal protective equipment were collected via questionnaires. Blood and urine samples and dermal wipes (sunflower oil) have been collected on two work days, before and after 6h of work. Particle-bound PAHs have been collected using personal pumps fitted with PM2.5 sampling inlets (37 mm Teflon filters) during the work hours. Gas-phase PAHs were collected using standard adsorbent tubes (XAD-2, 75/150 mg) with sample flow rate set at 2.7 L/min. The presence of coal tar in roof core was determined using a fluorescence scan. Levels of individual PAHs are being analyzed from air, plasma, urine samples (all with GC/MS) and dermal wipes (GC/TOFMS). Our early results suggest that smaller molecular PAHs, such as naphthalene (median 241.9 and 364.6 ng/m3 on day 1 and 2, respectively) and phenanthrene (median 48.7 and 90 ng/m3 on day 1 and 2, respectively) are the most abundant PAH in gaseous phase. We observed strong correlations between air levels of gaseous PAHs, such as naphthalene, phenanthrene, pyrene and anthracene (Spearman coefficients between 0.527 and 0.943 for, p<0.05 for all). Plasma PAHs were mostly below the quantification limit on both study days. Even though analyses of roof core samples did not indicate the presence of coal tar, 4-6 ring PAHs appear to predominate dermal wipe extracts.