Percutaneous Absorption of Polycyclic Aromatic Compounds from Fume Condensates of Paving and Built Up Roofing Asphalts

Abstract

Paving and roofing workers can be exposed to low levels of polycyclic aromatic compounds (PACs) while working with asphalt at elevated temperatures via both the inhalation and dermal routes. Inhalation exposure date are readily available. However, dermal information is more complicated and not as well-studied. Here we evaluate condensed fumes from four paving and four BURA asphalts for percutaneous absorption through human skin using in vitro studies. Test materials included eight asphalt (bitumen) fume condensates (AFCs) collected from the headspace above four paving and four Type III built up roofing asphalt (BURA) tanks, each proven to match worker breathing zone exposures. Sections of human cadaver skin were sliced with a dermatome to a thickness of 250–350 μm, one-inch circular pieces were mounted in Franz diffusion cells epidermis side up. Receptor fluids were sampled at intervals over 48 hr and the aliquots analyzed for PACs using HPLC with fluorescence detection to determine the dermal flux rates of anthracene, fluoranthene/pyrene, and total 3-6 ring PACs.

For paving/BURA AFCs, respectively, the average (N = 4) concentrations (μg/g) were: anthracene, 50.6 (SD = 14)/27.2 (SD = 28); fluoranthene/pyrene, 66.5 (SD = 47)/83.2 (SD = 100); Ʃ3-6 ring PACs, 833 (SD = 302)/2191 (SD = 240). Dermal flux rates (ng/cm²/hr) were: anthracene, 4.4 (SD = 1.1)/1.9 (SD = 2.0); fluoranthene/pyrene, 3.8 (SD = 2.8)/3.6 (SD = 5.0); Ʃ3-6 ring PAC, 35 (SD = 14)/21 (SD = 15). The estimated dermal flux of benzo[a]pyrene B[a]P in paving AFCs ranged from 0.0006 to 0.007 ng/cm²/hr and for BURA AFCs from 0.016 to 0.19 ng/cm²/hr. The averaged experimentally determined permeability coefficient (Kp) for anthracene for all eight samples was 0.90 ± 0.13 × 10⁻⁴ cm/hr (95% CI). Results show limited absorption of PACs across the skin in AFCs under the most conservative conditions (occluded/infinite dose). Dermal flux results can be used to support dermal exposure and risk assessments for asphalt emissions.

Keywords:

• Asphalt emissions
• Asphalt fume condensates (AFCs)
• BURA
• PAC

Acknowledgments

This project was sponsored by the Asphalt Institute (AI), an international trade association promoting the quality use of asphalt through their members, training and research. We thank all members of AI’s Health, Safety, and Environment committee and other scientists that reviewed this manuscript.

Disclosure statement

Dr. Roy reports personal fees from Asphalt Institute, during the conduct of the study. He is an affiliate of the University of South Carolina and was contracted to perform this skin painting research by the Asphalt Institute. The other two authors work for Heritage Research Group, the research arm of The Heritage Group which includes Asphalt Materials Inc.