Percutaneous absorption of benzene (71432), toluene (108883), ethylbenzene (100414), and aniline (62533) was investigated in male HRS/J-hairless-mice. Stainless steel skin depots containing 100 to 150 milligrams of solid sorbent were fixed to the backs of anesthetized mice and charged with about 5 microliters of carbon-14 tagged test solution. Expired air samples were obtained until 4 hours after exposure, when mice were killed and samples for radioactivity were obtained from the skin depot, the skin under the depot, a wiping of the skin under the depot, the carcass, feces, urine, and cage washings. Physical constants were determined for each test compound, including octanol/water partition coefficient, solubility, vapor pressure, melting and boiling points, and absorption and evaporation rates. Solvent recovery exceeded 90% in all mice, with highest recovery in the skin depot. Average administered doses were 3.94 milligrams (mg) benzene, of which 0.99% was absorbed; 3.89mg toluene (2.31% absorbed), 4.10mg ethylbenzene (3.61% absorbed), and 4.68mg aniline (4.76% absorbed). Excretion rate in expired air was fastest during the first 15 minutes of exposure except in mice treated with toluene or ethylbenzene, which demonstrated maximal excretion rate during the second 15 minutes after exposure. A two compartment model was suggested by the initial rapid and subsequent gradual decay of expired breath excretion. Vapor pressure and boiling point were significantly correlated with the applied radioactive dose absorbed. Absorption rates were found to be 56, 49, 37, and 2.3 micrograms per square centimeter per minute for benzene, toluene, ethylbenzene, and aniline, respectively.
Allan S. Susten, National Institute for Occupational Safety and Health. US Public Health Service, Centers for Disease Control, Division of Biomedical and Behavioral Science, Experimental Toxicology Branch, 4676 Columbia Parkway, Cincinnati, OH 45226, USA