Dermal absorption of polycyclic aromatic hydrocarbons in the blood-perfused pig ear.

Urinary 1-OH-pyrene, a metabolite of pyrene, is a sensitive biological marker for dermal absorption of pyrene in man. In order to determine whether this metabolite is a reliable biomarker of cutaneous absorption of other polycyclic aromatic hydrocarbons (PAHs), the blood-perfused pig ear model was used to compare the dermal absorption flux of pyrene with nine other PAHs after coal tar application. Cumulative absorption of PAHs into the perfusion blood, 200 min after application of an overdose of coal tar, ranged between 830 pmol cm-2 for phenanthrene to less than 4 pmol cm-2 for benzo[b]fluoroanthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[ah]anthracene and indeno[123-cd]pyrene. The results of this study show that when pyrene is used as a marker compound for PAH absorption through pig skin, the cumulative absorption of PAHs with a lower molecular weight will be underestimated: fluorene, tenfold; phenanthrene, 12-fold; anthracene and fluoranthene, ca. twofold. The percutaneous absorption of PAHs with a higher molecular weight than pyrene will be overestimated: e.g. benzo[a]pyrene, sevenfold; indeno [123-cd]pyrene, ca. 100-fold. It is likely that this conclusion is also valid for dermal PAH absorption in man.

Reduction of urinary 1-hydroxypyrene excretion in coke-oven workers exposed to polycyclic aromatic hydrocarbons due to improved hygienic skin protective measures.

The effect of hygienic skin protective measures on the internal exposure to polycyclic aromatic hydrocarbons (PAHs) was studied in 13 coke-oven workers. The study took place over 2 consecutive weeks. In 1 week the subjects worked under the normal circumstances, in the other week extra hygienic skin protective measures were instituted: laundered working clothes and a new pair of gloves before each 8-h work shift, and the washing both of the hands and of the face before each break. Biological monitoring was undertaken to measure the effect of the extra hygienic measures on the urinary 1-hydroxypyrene excretion, which is a measure of the internal PAH exposure. The increase of the urinary 1-hydroxypyrene concentration over the 4-day workweek was on average 37% lower when extra hygienic measures were taken, being 1.3 instead of 2.3 mumole 1-hydroxypyrene per mole creatinine (P = 0.03, N = 13). This study demonstrates that simple hygienic skin protective measures result in a significant reduction of the internal PAH exposure.

Estimation of individual dermal and respiratory uptake of polycyclic aromatic hydrocarbons in 12 coke oven workers.

Twelve workers from a coke plant in The Netherlands participated in an intensive skin monitoring programme combined with personal air sampling and biological monitoring during five consecutive eight hour workshifts. The purpose of the study was to make a quantitative assessment of both the dermal and respiratory intake of polycyclic aromatic hydrocarbons (PAHs). Pyrene was used as a marker compound for both dermal and respiratory exposure to PAHs. The biological measure for the internal exposure to PAHs was urinary 1-OH-pyrene concentration. Measurements on exposure pads at six skin sites showed that mean total skin contamination of the 12 workers ranged between 21 and 166 micrograms pyrene a day. The dermal uptake of pyrene ranged between 4 and 34 micrograms/day, which was about 20% of the pyrene contamination on skin. The mean concentration of total pyrene in the breathing zone air of the 12 coke oven workers ranged from 0.1 to 5.4 micrograms/m3. The mean respiratory uptake of pyrene varied between 0.5 and 32.2 micrograms/day. Based on the estimates of the dermal and respiratory pyrene uptake it is concluded that an average 75% (range 28%-95%, n = 12) of the total absorbed amount of pyrene enters the body through the skin. Because of the difference in the pyrene:benzo(a)pyrene ratio between the air samples and the skin contamination samples, the dermal uptake of benzo(a)pyrene was also estimated. This was about 51% of the total absorbed amount (range 8%-92%, n = 12). The total excreted amount of urinary 1-OH-pyrene as a result of exposure to PAHs during the five consecutive workshifts varied between 36 and 239 nmol. A multiple regression model of the mass balance between pyrene dose (both dermal and respiratory) and 1-OH-pyrene excretion confirmed the relevance of the dermal exposure route. The variation in urinary 1-OH-pyrene excretion was determined more by the dermal pyrene dose than by the respiratory dose. The model showed an estimate of the percentage of the absorbed amount of pyrene that is metabolised and excreted as 1-OH-pyrene in urine. For the 12 workers this percentage varied between 13% and 49% depending on smoking habits and consumption of alcohol. The results of this study indicate that among coke oven workers, the skin is the main route of uptake of PAHs. Preventive measures to reduce exposure to PAHs should be focused more on the reduction of dermal contamination by PAHs than on the reduction of inhaled dose.

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

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.

Dermal exposure to polycyclic aromatic hydrocarbons among primary aluminium workers.

Large amounts of PAH's are released in the electrode production departments of pre-bake cell aluminium reduction plants. Emission sources are mixing, shaping and baking of the anode (paste plant and bake oven) and pot relining operations. A study was performed to quantify the importance of dermal uptake of PAH's among exposed workers. Twenty workers in the anode production departments (paste plant (N = 8) and bake oven (N = 5)) and the pot relining department (N = 7) volunteered for the study. Monitoring was performed over a period of 5 consecutive days using personal air sampling, dermal contamination sampling and biological monitoring. Pyrene concentrations measured in the respirable air samples, ranged up to 320 micrograms/m3. Dermal contamination of pyrene was monitored at three skin sites (wrist, jaw/neck and groin) using exposure pads as pseudo-skin. The skin contamination with pyrene ranged up to 375 ng/cm2. Contamination of the groin skin site, although covered by work clothes ranged up to 106 ng/cm2. The concentration of 1-hydroxypyrene in pre and post-shift urine ranged up to 27 mumol/mol creatinine and showed an increase during the day and a decrease during the night. Pyrene in air and pyrene on the skin were tested for significance of correlation with urinary 1-hydroxypyrene in samples taken at several moments: end-of-shift, pre-shift next morning and weekly increase. The correlation coefficients between dermal contamination and urinary 1-hydroxypyrene were equal or higher than the correlation coefficient between pyrene air concentration and urinary 1-hydroxypyrene. The total skin contamination in exposed workers is estimated to be more than three times higher than the intake via the respiratory tract. The contribution of dermal exposure to the total PAH body burden of exposed workers therefore appears to be significant.