2-ethoxy-2-methylpropane

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.51 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

11 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.017 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

12.5 mg/L

Assessment factor:

1

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

2.86 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.078 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.274 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

As no complete data set is available for ETBE, the missing endpoints will be filled using read-across from either MTBE or TAME. Comparing all available experimental results on toxicity of ETBE, MTBE and TAME, it seems likely that the chronic toxicity of ETBE is expected to be more similar to TAME than to MTBE. When read-across is used from TAME to ETBE a safety factor of 2 will be taken into account. However, in cases that only results are available for MTBE, these will be taken for read across and a safety factor of 10 will be applied effect parameters.

Only one reliable study is available for freshwater fish. The study is a non-GLP compliant OECD guideline study with the guppyPoecilia reticulata. The purity of the test substance was not known and the effect concentrations were based on nominal values. The 96 -h LC50 is > 974 mg/l. As no data is available for marine fish the data from MTBE are used for read-across, the lowest effect concentration in marine fish for MTBE is a 96-h LC50 of 574 mg/l in inland silverside (Menidia beryllina), applying a safety factor of 10 to this value results in an effect concentration of 57.4 mg/l for ETBE. Both values will be used in the assessment.

No chronic studies in fish are available for ETBE, an ELS test with eggs and larvae/fry of fathead minnow (Pimephales promelas) is available for MTBE. This result is used for read-across, the 31-d NOEC is 299 mg/l and a safety factor of 10 will be applied to this value. An effect concentration of 29.9 mg/l for ETBE will be used in the assessment.

Two studies are available for freshwater invertebrates; one study is a GLP compliant OECD guideline study withDaphnia magna.The 48-h EC50 value from this study is 110 mg/l and is more critical than the other study which is also an OECD guideline study, but which has minor deviations. Furthermore, a study with the marine speciesAmericamysis bahia(tested asMysidopsis bahia) is available, the 96-h LC50 is 37 mg/l. These values are used in the assessment.

No chronic studies in invertebrates are available for ETBE, chronic studies are, however, available for MTBE and TAME. A guideline study is available for MTBE withDaphnia magna, the 21-d NOEC is 51 mg/l. A safety factor of 10 is applied to this value, resulting in an effect concentration of 5.1 mg/l for ETBE. For marine inverbrates a chronic guideline study is available for TAME withAmericamysis bahia. The 28-d NOEC is 3.39 mg/l, applying a safety factor of 2 results in an effect concentration of 1.7 mg/l for ETBE. These values are used in the assessment.

Two studies are available for algae; one study is a GLP compliant OECD guideline study withPseudokirchneriella subcapitata(tested asSelenastrum capricornutum), the 72-h ErC50 value from this study is 1,100 mg/l and the 72-h NOEC is 7.5 mg/l. The effect concentrations from this study are more critical than the other study which is an OECD guideline study withDesmodesmus subspicatus, but this study has minor deviations. These values are used in the assessment.

No studies with micro-organisms are available for ETBE; a study withPseudomonas putidais available for TAME, the 16-h EC10 is 25 mg/l, applying a safety factor of 2 to this value results in an effect concentration of 12.5 mg/l for ETBE. This value will be used in the assessment.

No studies with sediment and terrestrial organisms are available, however as the log Kow is very low (1.48) direct and indirect exposure of these compartments is not expected as was demonstrated by the exposure assessment.

No data on bird toxicity is available, however a large mammalian dataset is available and as the log Kow is very low (1.48) secondary poisoning is not expected.

Conclusion on classification

A limited set of ecotoxicity/environmental data is available for this substance, thus data from similar ethers are considered. 

Only one reliable study for this substance is available for freshwater fish that reported a 96-h LC50 of > 974 mg/l in guppy (Poecilia reticulata). As no data is available for marine fish, data from MTBE are used for read-across; the lowest effect concentration in marine fish for MTBE is a 96-h LC50 of 574 mg/l in inland silverside (Menidia beryllina), a safety factor of 10 will be applied on this value. No chronic studies in fish are available for this substance; however, an ELS test with eggs and larvae/fry of fathead minnow (Pimephales promelas) is available for MTBE. The 31-d NOEC for MTBE in the freshwater fishPimephales promelasis 299 mg/l, a safety factor of 10 will be applied on this value.

Two studies are available for freshwater invertebrates, with the more reliable study reporting a 48-h EC50 value of 110 mg/l inDaphnia magna. A study with the marine speciesAmericamysis bahia(tested asMysidopsis bahia) is available, the 96-h LC50 is 37 mg/l. No chronic studies in invertebrates are available for this substance, however chronic studies are available from MTBE and TAME. The 21-d NOEC for MTBE inDaphnia magnais 51 mg/l, applying a safety factor of 10 results in a NOEC of 5.1 mg/l for ETBE. For marine invertebrates the 28-d NOEC for TAME is 3.39 mg/l inAmericamysis bahia, applying a safety factor of 2 results in an NOEC of 1.7 mg/l for ETBE. Two studies with algae are available; the more reliable keystudy withPseudokirchneriella subcapitata(tested asSelenastrum capricornutum) reported a 72-h ErC50 of 1,100 mg/l and a 72-h NOEC of 7.5 mg/l. No studies with micro-organisms are available for this substance; a study withPseudomonas putidais available for TAME that found a 16-h EC10 of 25 mg/l, a safety factor of 2 will be applied on this value.

No studies with sediment and terrestrial organisms are available, however as the log Kow is very low (1.48) direct and indirect exposure of these compartments is not expected as was demonstrated by the exposure assessment. 

No data on bird toxicity is available, however a large mammalian dataset is available and as the log Kow is very low (1.48) secondary poisoning is not expected.

According to Directive 67/548/EEC, results of validated structure activity relationships and expert judgment may also be taken into account where appropriate with regard to classification and labelling of substances. The lowest acute aquatic toxicity value is between 10 and 100 mg/l for a marine invertebrateAmericamysis bahia(tested asMysidopsis bahia). Test results show values above 100 mg/l for freshwater fish, algae andDaphnia. The substance is not bioaccumulative judging by the log Kow of 1.48 and the substance is not readily biodegradable.

The 96h LC50 of 37 mg/l forAmericamysis bahiadoes not result in classification under Directive 67/548/EEC or EU CLP (Regulation (EC) No. 1272/2008), because the chronic NOEC values (read-across from MTBE and TAME) are larger than 1 mg/l.