Superfund Research Program
Human Dosimetry for Assessment of Exposure to Volatile Compounds
Project Leader: Michael S. Morgan
Grant Number: P42ES004696
Funding Period: 1995 - 2006
Final Progress Reports
Year: 2005 1999
Studies of human exposure to methyl tertiary butyl ether (MTBE) are now under way, and the physiologically based toxicokinetic model developed and tested earlier for toluene has been modified to fit the data for blood, breath and urine samples taken from the exposed subjects. With appropriate modifications, the model appears to fit the experimental data very well. Additional subjects will be recruited and given exposure to MTBE to complete this data set. Using urine samples collected from a subset of the cohort of subjects exposed to toluene, a detailed analysis was performed to investigate the value of correcting urinary concentrations using creatinine and specific gravity. Subjects provided complete urine voids for at least 24 hours after the end of exposure, and each sample was analyzed separately for hippuric acid, creatinine, and specific gravity, as well as void volume and time. Multiple regression analyses indicate that urinary correction using any of the methods evaluated improved the relationship between metabolite concentration and dose, in the first 12 hours after exposure. For samples collected later than 12 hours, variability in metabolite concentrations was not improved by correction.