Absorption and evaporation of volatile and potentially hazardous chemicals from human skin
V.D. Bhatt*, M. Miller, G.B. Kasting
University of Cincinnati, Cincinnati, United States
Purpose
To test an existing kinetic model for disposition of volatile compounds from human skin and develop a predictive mathematical model based on diffusion theory that improves significantly on current predictions and extends the range of validity to pesticides and non-corrosive industrial solvents.
Methods
Split thickness human cadaver skin was mounted on modified Franz diffusion cells connected to a customized volatiles trap using Tenax® cartridges. Diffusion cells, filled with phosphate buffered saline (pH 7.4 with 0.02% sodium azide) were maintained at 37 ± 2 °C. A 1%w/w solution of 14C-N, N-diethyl-3-methylbenzamide (14C-DEET) was applied on to the skin. Evaporation and absorption of 14C-DEET were measured at varying airflows (v =10-100 mL/min, n = 2-6 per airflow). Receptor solutions were analysed by liquid scintillation counting. Tenax® cartridges were thermally desorbed and analysed similarly. Results were analysed according to one- and two-compartment kinetic models and a numerical diffusion evaporation model.
Results
Evaporation rate increased in direct proportion to airflow. The percent of dose evaporated after 24 h ranged from 16 ± 4 % at v =10 mL/min to 53 ± 7% at v = 80 mL/min. Compartmental analyses satisfactorily correlated the results; however, the reduced parameters obtained from these analyses did not agree with those obtained from a previous study with benzyl alcohol. The diffusion/evaporation model yielded more easily interpretable parameters with better agreement between the two studies.
Conclusion
Evaporation and absorption of solvent deposited volatile compounds from skin can be satisfactorily described by a diffusion model employing accessible physical properties and a simple representation of the skin barrier.
Content last modified: 21 May 2005
