Ethers, C5-6-branched alkyl Me

Endpoint summary

Additional information

Based on the considerations described in the attached 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 aquatic toxicity of the substance ‘C5-6 branched alkylmethyl-ethers’ with sufficient certainty.

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 where needed

Tuppurainen et al. (2007) and Niska et al. (2008) calculated the aquatic toxicity of TAME and C5-6 branched alkylmethyl-ethers 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 for fish and daphnids for C5-6 branched alkylmethyl-ethers. The weighted averages for each of the endpoints are given below.

 

Weighted average values for different ecotoxicological endpoints

 

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

 

The outcome of the following studies are used to support the approach to derive the effect concentration as a weighted average of the predicted values for the components of the substance (see the document “Read-across substantiation C5-6 branched alkylmethyl-ethers”):

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 inOnchorhynchus mykiss(Springborn Laboratories, Inc., 1994a). 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) (BenKinney et al., 1994), applying a safety factor of 10 to this value results in an effect concentration of 57.4 mg/l for TAME

No chronic studies with fish are available for TAME. An ELS test with eggs and larvae/fry of fathead minnow (Pimephales promelas) is available for MTBE (ENSR, 1999). 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.

There are several guideline studies available for freshwater invertebrates. The most critical study is chosen as the key study. For freshwater invertebrates the lowest observed effect concentration is a 48-h EC50 value of 100 mg/l inDaphnia magna(Springborn Laboratories, Inc., 1994b). For marine invertebrates only one study was available, the study was conducted according to accepted guidelines, the 96-h LC50 is 14 mg/l inAmericamysis bahia(Springborn Laboratories, Inc., 1994c).

One chronic test with marine invertebrates is available; the study is conducted according to accepted guidelines. The 28-d NOEC inAmericamysis bahiais 3.39 mg/l (T. R. Wilbury Laboratories, Inc., 2004). No chronic studies with freshwater invertebrates are available. A guideline study is available for MTBE withDaphnia magna, the 21-d NOEC is 51 mg/l (Wildlife International Ltd., 1999). Applying a safety factor of 10 to this value results in an NOEC of 5.1 mg/l for TAME.

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 (Springborn Laboratories Inc., 1995). 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 inPseudokirchneriella subcapitata(SafePharm Laboratories, 2003a). These values are used in the assessment since no data are available to support the derivation of a weighted average value.

One study withPseudomonas putidais available for TAME, which is conducted according to ISO 10712, the 16-h EC10 is 25 mg/l (SafePharm Laboratories, 2003c). This value is used in the assessment since no data are available to support the derivation of a weighted average value.

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