2-methoxy-2-methylbutane

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):

10 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.034 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

25 mg/L

Assessment factor:

1

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

2.99 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.199 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.301 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Additional information

As no complete data set is available for TAME, the missing endpoints will be filled using read-across from MTBE. Comparing all available experimental results on toxicity of ETBE, MTBE and TAME, it seems likely that the chronic toxicity of TAME is expected to be more similar to ETBE than to MTBE. However, there is no data for ETBE that can cover the endpoints for TAME. Therefore, the results from MTBE will be taken for read across and a safety factor of 10 will be applied on the effect parameters.

A general problem in testing the toxicity of TAME to aquatic organisms is the volatility of the substance. The vapour pressure shows TAME to be highly volatile and according to the Henry’s law constant the volatility from water is also very high. Volatilisation has been prevented as much as possible in the test designs and measured concentrations are essential when validating the tests.

There are three guideline studies available for freshwater fish. The studies are either semi-static or flow-through. The most critical study is therefore chosen as the key study. The lowest observed effect concentration is a 96-h LC50 value of 580 mg/l in Onchorhynchus mykiss. As no data are 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 TAME. Both values will be used in the assessment.

No chronic studies with fish are available for TAME, however 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 TAME will be used in the assessment.

There are several guideline studies available for freshwater invertebrates. The most critical study is therefore chosen as the key study. For freshwater invertebrates the lowest observed effect concentration is a 48-h EC50 value of 100 mg/l in Daphnia magna. For marine invertebrates only one study was available; the study was conducted according to accepted guidelines and gave a 96-h LC50 of 14 mg/l in Americamysis bahia. Both values will be used in the assessment.

One chronic test with marine invertebrates is available; the study is conducted according to accepted guidelines. The 28-d NOEC in Americamysis bahia is 3.39 mg/l. No chronic studies with freshwater invertebrates are available. A guideline study is available for MTBE with Daphnia 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 TAME. These values are used in the assessment.

Several studies with algae are available; all are conducted according to accepted guidelines. One study was considered invalid as test concentrations could not be maintained and the cell concentration in the controls in all replicates was smaller after 72 hours than after 48 hours. From the other studies the most critical study is chosen as the key study. The lowest 72-h ErC50 value is 780 mg/l and the 72-h NOEC is 77 mg/l in Pseudokirchneriella subcapitata. These values are used in the assessment.

One study with Pseudomonas putida is available for TAME, which is conducted according to ISO 10712, the 16-h EC10 is 25 mg/l. 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 (1.55) 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 (1.55) 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.

There are three guideline studies available for freshwater fish. The lowest observed effect concentration is a 96-h LC50 value of 580 mg/l in Oncorhynchus mykiss. 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). No chronic studies with fish are available for this substance; however, an ELS test with eggs and larvae/fry of fathead minnow (Pimephales promelas) is available for MTBE that found 31-d NOEC of 299 mg/l.

There are several guideline studies available for freshwater invertebrates. The lowest observed effect concentration is a 48-h EC50 value of 100 mg/l in Daphnia magna. For marine invertebrates only one study is available, the 96-h LC50 is 44 mg/l in Americamysis bahia.

One chronic test with marine invertebrates is available. The 28-d NOEC in Americamysis bahiais 3.39 mg/l. No chronic studies with freshwater invertebrates are available for this substance, however, a chronic study for is available for MTBE with Daphnia magna, the 21-d NOEC is 51 mg/l.

Several studies with algae are available. The lowest 72-h ErC50 value is 780 mg/l and the 72-h NOEC is 77 mg/l in Pseudokirchneriella subcapitata.

One study with micro-organisms (Pseudomonas putida) is available for this substance that found the 16-h EC10 of 25 mg/l.

No studies with sediment and terrestrial organisms are available, however as the log Kow is very low (1.55) 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 (1.55) secondary poisoning is not expected.

Based on all available environmental fate and ecotoxicological data for daphnids, fish and algae, this substance does not need to be classified according to the EU CLP (Regulation (EC) No. 1272/2008). Although the lowest reliable acute effect concentration is between 10 and 100 mg/l and this substance is not readily biodegradable, the substance is not bioaccumulative. All reliable chronic NOECs are greater than 1 mg/l which leads to non-classification.