ToxSci Advance Access originally published online on August 10, 2005
Toxicological Sciences 2005 88(1):30-38; doi:10.1093/toxsci/kfi281
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Uptake and Disposition of Inhaled Methanol Vapor in Humans


* Work Environment Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden;
Department of Health and Psycosocial Medicine, Aichi Medical University School of Medicine, Nagakute-cho, Japan; and
Work Environment Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
Received May 23, 2005; accepted July 11, 2005
Methanol is a widely used solvent and a potential fuel for motor vehicles. Human kinetic data of methanol are sparse. As a basis for biological exposure monitoring and risk assessment, we studied the inhalation toxicokinetics of methanol vapor in four female and four male human volunteers during light physical exercise (50 W) in an exposure chamber. The relative uptake of methanol was about 50% (range 4753%). Methanol in blood increased from a background level of about 20 to 116 and 244 µM after 2 h exposure at 0, 100 ppm (131 mg/m3) and 200 ppm (262 mg/m3), respectively. Saliva showed substantially higher levels than blood immediately after exposure. This difference disappeared in a few minutes; thereafter the concentrations and time courses in blood, urine, and saliva were similar, with half times of 1.4, 1.7, and 1.3 h, respectively. The postexposure decrease of methanol in exhaled air was faster, with a half time of 0.8 h. The methanol concentrations were approximately twice as high in all four types of biological samples at 200 compared to 100 ppm. No increase in urinary formic acid was seen in exposed subjects. Our study indicates nonsaturated, dose-proportional kinetics of methanol up to 200 ppm for 2 h. No gender differences were detected. Similar, parallel patterns were seen with regard to the methanol time courses in blood, urine, and saliva, whereas the concentration in exhaled air decreased markedly faster. Thus, apart from blood and urine, saliva also seems suitable for biomonitoring of methanol exposure.
Key Words: methanol; inhalation; toxicokinetics; human; biomonitoring; gender.