Pentachlorophenol dermal absorption and disposition from soil in swine: effects of occlusion and skin microorganism inhibition.

Residue of the environmentally relevant biocide pentachlorophenol (PCP) is found mainly in soil, making dermal contact one of the primary routes for PCP exposure. To quantify exposure effects on dermal absorption and systemic disposition, [14C-UL]PCP was dosed nonocclusively or occlusively at 40 micrograms/cm2 in a soil-based mixture in an in vivo swine model. Additionally, antibiotics were also codosed with occlusive PCP in soil to examine the impacts of skin microbial PCP biodegradation on total dermal absorption. Under nonocclusive, occlusive, and occlusive-antibiotic conditions, total radiolabel absorption by 408 hr was 29.08, 100.72, and 86.21% dose, respectively. Tissue accumulation of PCP and its labeled metabolite(s) was very significant in swine since one-half to two-thirds of the absorbed dose was still present in tissues by 17 days after PCP dermal exposure. High 14C concentrations were found in liver, kidney, lung, ovary, and uterus. Urine and fecal routes were equally important for label excretion from the body. Occlusion enhanced total dermal absorption and changed the shape of the absorption profiles in the blood and plasma. Skin microorganism inhibition retarded 14C dermal absorption, altered local and systemic tissue distribution, and increased plasma/blood concentration ratios, suggesting skin microbial PCP degradation might play an important role in the altered absorption and disposition by occlusion. This study demonstrated significant dermal absorption and extensive tissue persistence of PCP after soil exposure. Occlusion and skin microflora growth may greatly impact dermal absorption, cutaneous disposition, and systemic toxic input. Therefore, exposure-specific PCP absorption and disposition profiles must be taken into consideration in risk analysis.