Registration Dossier
Registration Dossier
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EC number: 211-309-7 | CAS number: 637-92-3
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
A QSAR-derived permeability coefficient (Kp) for ETBE was available. Furthermore, an experimentally derived Kp for MTBE, a highly similar substance, was available. The QSAR-derived Kp was 0.0063 cm/hour and the experimentally derived Kp of MTBE was 0.0035 cm/hour after correction for the higher temperature. For the calculation of the percentage absorption, the aqueous Kp of 0.0063 cm/hour was used.
Key value for chemical safety assessment
- Absorption rate - dermal (%):
- 0.3
Additional information
Absorption and distribution
ETBE is rapidly absorbed and distributed into the blood after inhalation exposure. In humans, the respiratory uptake of ETBE was 32-34%. Absorption becomes saturated at higher concentrations in rats and mice (> 1750 ppm).
Metabolism
Tert-butyl alcohol (TBA), a TBA conjugate, 2-methyl-1,2-propanediol, and 2-hydroxyisobutyrate were found to be metabolites of ETBE in rats and humans. In addition, trace amounts of acetone were present in urine.
After inhalation exposure of 4 and 40 ppm of ETBE, urinary excretion of metabolites was less in the rats than in humans exposed under identical conditions and urinary half-lives in rats were also shorter than in humans. Unchanged ETBE was not detected in rat urine, but it was present in human urine.
Elimination
Elimination is mainly in urine and exhalation and most of the elimination takes place during the first two days in both rodent species. The elimination in urine is mainly in 2-hydroxyisobutyrate. ETBE is exhaled more than TBA shortly after the exposure but later TBA becomes prominent. ETBE was eliminated from the blood with a half-life of 0.4-0.6 hr.
Information used for DNEL derivation
The inhalation and dermal absorption percentages used for DNEL derivation (in case of route-to-route extrapolation) are 40% and 0.3%, respectively. No data on oral absorption for ETBE is available. However, based on the available data for the two structure analogues MTBE and TAME, 100% oral absorption is assumed.
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