In vitro percutaneous absorption of cadmium from water and soil into human skin

Abstract

The objective was to determine percutaneous absorption of cadmium as the chloride salt from water and soil into and through human skin. Soil (Yolo County 65-California-57-8) was passed through 10-, 20-, and 48-mesh sieves. Soil retained by 80 mesh was mixed with radioactive cadmium-109 at 13 ppb. Water solutions of cadmium-109 at 116 ppb were prepared for comparative analysis. Human cadaver skin was dermatomed to 500-μm, and used in glass diffusion cells with human plasma as the receptor fluid (3 ml/hr flow rate) for a 16-hr skin application time. Cadmium in water (5 μl/cm 2) penetrated skin to concentrations of 8.8 ± 0.6 and 12.7 ± 11.7% of the applied dose from two human skin sources. Percentage doses absorbed into plasma were 0.5 ± 0.2 and 0.6 ± 0.6%, respectively. Cadmium from soil (0.04 g soil/cm 2) penetrated skin at concentrations of 0.06 ± 0.02 and 0.13 ± 0.05% for the two human skin sources. Amounts absorbed into plasma were 0.01 ± 0.01 and 0.07 ± 0.03%. Most of the nonabsorbed cadmium was recovered in the soap and water skin surface wash. Binding of cadmium from water to soil was greater than binding from water to powdered human stratum corneum, supporting the lower absorption from soil than from water. Short-term exposure of cadmium in water to human skin for 30 min (bath or swim) resulted in skin uptake, which upon further perfusion (48 hr), absorbed into the plasma receptor fluid (systemic). Cadmium in soil was increased from 6.5 to 65 ppb. Skin levels correspondently increased, but plasma receptor fluid levels remained constant. Soil capacity was decreased from 40 to 4 mg/cm 2. Skin levels correspondingly decreased, suggesting decreased skin contact, but plasma receptor fluid levels remained constant. The above suggest that, with in vitro diffusion, the surface concentration of cadmium will influence skin cadmium concentration, but that absorption into plasma receptor fluid is relatively independent of skin surface concentrations. Calculations suggest that a daily whole body exposure to cadmium at 116 ppb with 0.5% absorption will result in daily systemic intake of about 10 μg cadmium.