Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

MTBE is resistant to hydrolysis within environmentally relevant pH ranges as demonstrated in an OECD guideline, GLP-compliant study. Strong acids can contribute to the hydrolysis of MTBE, but the pH range in which this would occur is below typical ranges found in natural soil and water ( Lyman et al. 1982).

The degradation half-life of MTBE in the air is calculated to range between 3-6 days depending on environmental conditions (primarily OH-radical concentration).

The atmospheric half-life of MTBE is estimated at 5.65 days, based on degradation rate constant of 2.84E-12 cm3/molecule/s and a radical concentration of 5E05 radicals/cm3. The half-life represents a degradation rate in non-polluted air, rather than polluted air where half-lives typically are shorter due to a higher concentration of reactive radical components.

Direct photolysis will not be an important removal process of MTBE in water because aliphatic ethers do not absorb light at wavelengths, >290 nm, that are responsible for this process. The MTBE UV-spectrum, max t 289 nm, indicates that there is a low potential for direct photolysis in water.

The rate constant used in the assessment are:

Degradation for hydrolysis

0 d-1

Degradation for photolysis

0 d-1

Degradation in air

0.123 d-1