Percutaneous Absorption of Polycyclic Aromatic Compounds from Bitumen Fume Condensate

Abstract

Bitumen fume condensate was obtained from the headspace vapors of a bitumen storage tank containing a lightly oxidized paving-bitumen for the purpose of developing an in vitro procedure to estimate the percutaneous absorption, through human skin, of the very low levels of polycyclic aromatic compounds found in the condensate. The Fraunhofer Institute of Toxicology and Medicine provided the fume condensate and analyses of the individual polycyclics present. Heritage Research Group provided analyses of total 3–6 ring polycyclics. Sections of human back skin were sliced with a dermatome to a thickness of ∼ 250 μ m, and 1-inch circular pieces were mounted in 6 Franz diffusion cells. Tissue integrity was assured by electrical resistance measurement. Neat condensate was applied to the stratum corneum at “infinite dose” (200 μ l) while the dermis was in direct contact with a receptor fluid consisting of an aqueous solution of polyoxyethylene 20 oleyl ether. Receptor fluids were sampled at 12 intervals over 48 hours, and analyzed by an HPLC system equipped with a variable wavelength detector and a fluorescence detector connected in series. The UV detector was generally operated at 254 nm, and the fluorescence detector at ex360nm/em400nm, 18 nm bandpass. The mobile phase was a 60–100% acetonitrile/water gradient. Penetration rates of anthracene, fluoranthene-pyrene, and total 3–6 ring polycyclic aromatic compounds (PAC) were measured. The neat condensate was 32.7 μ g/g anthracene, 7.4 μ g/g fluoranthene, 7.3 μ g/g pyrene, and 1.8 mg/g total 3–6 ring PAC. The rates of dermal penetration (ng/cm²/hr ± SD) were: anthracene 6.5 ± 0.9; fluoranthene-pyrene 1.8 ± 0.3; and 3–6 ring PAC 120 ± 30. Percentages of applied dose absorbed were: anthracene 5.3%, fluoranthene-pyrene 3.3%, and 3–6 ring PAC 1.8%. The apparent permeability coefficient Kp (Kp = flux rate/applied concentration) for anthracene was 2 × 10^{− 4} cm/hr. These results demonstrate that penetration of PAC, at the low concentrations found in bitumen fume condensates, can be measured by an appropriately designed in vitro method. Rates of PAC percutaneous absorption will be further evaluated in the future with other fume condensates obtained from several different straight run paving asphalts.

Keywords:

• percutaneous absorption
• polycyclic aromatic compounds
• bitumen fume
• polycyclic aromatic hydrocarbons
• PAH
• PAC

Notes

^A Values from Table 4-33 ^{( 7 )}.

^B Values from Table 4-33^{( 7 )} expressed /cc (fume condensate density = 0.8985).

^C Values estimated based on the experimentally determined value for anthracene flux, and published SAR models and data for PAC absorption.^{( 6 )}

^D Dermal flux = (concentration in μ g/cm³) × (permeability constant (Kp).

^E Flux value experimentally determined in this study.