Ethers, C5-6-branched alkyl Me

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.44 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

8.5 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.044 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:

5.1 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.51 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:

0.766 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

8 330 g/kg food

Assessment factor:

300

Additional information

Based on the considerations described in Annex C (document “Read-across substantiation C5-6 branched alkylmethyl-ethers”, incl. the supporting references Tuppurainen et al., 2007 and Niska et al., 2008), it can be concluded that the available information can be used to predict the ecotoxicological properties of the substance ‘C5-6 branched alkylmethyl-ethers’ with sufficient certainty.

Based on the calculated molecular descriptors, it can be concluded that TAME, MTBE, ETBE and NExTAME-ethers are closely related substances (see attached document). With regard to the physico-chemical properties, the NExTAME-ethers are slightly larger in size in comparison with TAME, MTBE, and ETBE, making them consequently more hydrophobic. Due to the higher molecular weight and lower water solubility of the NExTAME-ethers, they have a weaker potential for widespread environmental distribution in comparison with TAME, MTBE, and ETBE. On the other hand, the NExTAME-ethers may interact with mammalian and environmental systems with higher affinity due to their predicted higher hydrophobicity and bioconcentration factor. The electronic properties (such as dipole moments, frontier orbital energies, electron densities, and partial charges) are similar throughout the ether-series, suggesting that there should be no large differences in basic chemical reactivity. This indicates that it is reasonable to assume that the basic mode of action of the NExTAME-ethers is non-polar narcosis.

In addition to the molecular descriptors, Tuppurainen et al. (2007) and Niska et al. (2008) calculated the aquatic toxicity using ECOSAR.

The acute and chronic effect levels of TAME for fish were both under-estimated by a factor of about 5 and 2.5 respectively, indicating that the actual toxicity potential of TAME was lower than the predicted toxicity potential. The effect levels forDaphniawere predicted quite accurately. For both, fish and daphnids the predicted effect levels for NExTAME-ethers were lower than for TAME (up to a factor of 6), indicating a higher toxicological potential for the environment of the NExTAME-ethers (Niska et al., 2008 and Tuppurainen et al., 2007). To take into account this higher toxicological potential of the NExTAME-ethers compared to TAME a weighted average was calculated for acute and chronic effect levels regarding fish and daphnids for C5-6 branched alkylmethyl-ethers. The weighted averages for each of the endpoints are given below.

Endpoint	Weighted average (mg/l)
Acute toxicity to fish	85
Chronic toxicity to fish	11
Acute toxicity to daphnids	88
Chronic toxicity to daphnids	4.4

For the derivation of the PNECaquatic, PNECmarine and PNECintermittent releases the weighted averages were used instead of the data from TAME as this represent a worst-case approach. For the derivation of the PNECstp and the PNECoral the data from the TAME dossier were taken into account as no data is available for these endpoints to calculate a weighted average.

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 low (≤3), 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 (≤3) secondary poisoning is not expected.

Conclusion on classification

A limited set of ecotoxicity/environmental data is available for TAME, thus data from similar ethers (i.e. experimental MTBE-data and predicted values of the components of C5-6 branched alkylmethyl-ethers) are also considered.

Weighted average values were calculated for acute and chronic effect levels for fish and daphnids for C5-6 branched alkylmethyl-ethers. These calculations resulted for fish in effect levels of 85 mg/L for chronic exposure and 11 mg/L for acute expousure. For daphnids these values are 88 mg/L and 4.4 mg/L for acute and chronic exposure, respectively.

Several studies with algae are available for TAME. 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) for TAME is available which reported a 16-h EC10 of 25 mg/L.

No studies with sediment and terrestrial organisms are available, however as the log Kow is very low (≤3), 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 (≤3), secondary poisoning is not expected.

 

Based on all available environmental fate and ecotoxicological data for daphnids, fish and algae, the substance does not need to be classified according to Directive 67/548/EEC and the EU CLP (Regulation (EC) No. 1272/2008). Although the lowest reliable acute effect concentration is between 10 and 100 mg/L and C5-6 branched alkylmethyl-ethers is not readily biodegradable, the substance is not bioaccumulative. All reliable chronic NOECs are greater than 1 mg/L which leads to non-classification of C5-6 branched alkylmethyl-ethers.