In Vitro Penetration of Pig Skin by Heavy Metals in Soil

The potential health risk from exposure to heavy metal contaminated soil is often based on the quantity of metal that can be removed from soil by vigorous extraction procedures. This approach can overestimate risk since it ignores complex interactions between metals and soil that can result in a reduction in the amount of metal that desorbs from soil and is subsequently absorbed by the body. The aim of this research was to determine the relative contribution of the soil matrix and heavy metal sequestration in soil with time (“aging”) on the dermal penetration of arsenic, mercury, and nickel, respectively, as arsenic acid, mercuric chloride, and nickel chloride. In vitro flow-through diffusion cell studies were performed utilizing dermatomed male pig skin and radioactive compounds to measure total penetration (the sum of each metal in receptor fluid and skin). For arsenic and nickel, the soil matrix produced a 78–87% reduction in dermal penetration compared to 12–19% after aging. A greater effect was observed with aged mercury (52–56% decrease in dermal penetration) than in freshly spiked soil (40–43%). The results indicate that the potential health risk from dermal exposure to the metals can be significantly reduced by soil and aging.

Keywords:

• Arsenic
• mercury
• nickel
• dermal contact
• matrix effect
• aging.

Acknowledgment

This research was supported through funding from the Hazardous Substance Management Research Center and the New Jersey Commission on Science and Technology.

Notes

^a Mean ± SEM of percent initial dose for n = 10–14 replicates per treatment from three pigs.

^b Sum of receptor fluid and skin.

^c Significantly different from pure arsenic (p < 0.05, ANOVA).

^d Significantl different from arsenic in freshly spiked Atsion soil (p < 0.05, ANOVA).

^e Significantly different from corresponding treatment in Atsion soil (p < 0.05, Student's independent t-test).

^a Mean ± SEM of percent initial dose for n = 8–14 replicates per treatment from three pigs.

^b Sum of receptor fluid and skin.

^c Significantly different from pure mercury (p < 0.05, ANOVA).

^d Significantly different from mercury in freshly spiked Atsion soil (p < 0.05, ANOVA).

^e Significantly different from mercury in freshly spiked Keyport soil (p < 0.05, ANOVA).

^a Mean ± SEM of percent initial dose for n = 10–17 replicates per treatment from three-four pigs.

^b Sum of receptor fluid and skin.

^c Significantly different from pure nickel (p < 0.05, ANOVA).

^d Significantly different from nickel in freshly spiked Atsion soil (p < 0.05, ANOVA).

^e Significantly different from nickel in freshly spiked Keyport soil (p < 0.05, ANOVA).

^f Significantly different from nickel aged in Atsion soil (p < 0.05, Student's independent t-test).