Measurement of Toluene Emanating from the Surface of Human Skin in Relation to Toluene Inhalation

Background: Humanskin gas isknownas traces of gas emanating from thehumanskin. Exogenous chemicals such as toluenemay be released from the skin surface when absorbed into the body. However, dermal emission of toluene has not been fully determined in relation to inhalation exposure. Objectives: This study aimed to characterise the mechanism of toluene emanating from the skin surface of healthy volunteers in relation to inhalation exposure. Methods: Dermal emission flux of toluene was determined in healthy volunteers employing a passive flux sampler and gas chromatography-mass spectrometry. Results: The dermal emission of toluene occurs when toluene is absorbed by inhalation. The half-life obtained from the decrease in the dermal emission flux suggested the time-course of the dermal emission corresponds to that of the blood concentration. The whole-body emission rate of toluene was estimated to be 9.9% of the uptake rate by inhalation exposure. This suggests the toluene is excreted approximately 80% through urine, 7% - 14% by exhaled air, and 10% from the skin surface. Conclusions: This demonstrates that dermal emission is a newly discovered route of excretion of toluene from the human body and that dermal toluene might indicate the individual biological susceptibility to inhalation exposure to toluene.