Absorption of polycyclic aromatic hydrocarbons through human skin: Differences between anatomical sites and individuals

Abstract

In order to determine differences in absorption of polycyclic aromatic hydrocarbons (PAH) between anatomical sites and individuals, coal-tar ointment was applied to skin of volunteers at various sites. The surface disappearance of PAH and the excretion of urinary 1-OH-pyrene after skin application of coal-tar ointment were used as parameters for dermal PAH absorption. The surface disappearance was determined by the measurement of the fluorescence of PAH on skin. Surface disappearance measurements show low but significant differences in dermal PAH absorption between anatomical sites: shoulder > forehead, forearm, groin, > ankle, hand (palmar site). The average PAH absorption rate constant at different skin sites ranges from 0.036/h to 0.135/h (overall mean: 0.066/h). This indicates that after 6 h of exposure, 20-56% of a low dermal dose of PAH (e.g., about 1.0 ng pyrene/cm2) will be absorbed. The interindividual differences in PAH absorption are small (7%) in comparison with differences between anatomical sites (69%). Results based on the urinary excretion of 1-OH-pyrene are less clear. The site of application of the coal-tar ointment (dose: 2.5 mg/cm2 during 6 h) has no significant effect on the excreted amount of 1-OH-pyrene in urine. It is estimated that after coal-tar ointment application on skin, 0.3-1.4% of the pyrene dose (about 2 micrograms pyrene/cm2) becomes systemically available. For the accurate estimation of PAH uptake through skin of workers, it seems relevant to distinguish different body regions, not only because of the regional variation in percutaneous PAH absorption, but also because of the high dispersal of PAH contamination on skin of workers.