Alcohols, C11-15-secondary, ethoxylated

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity, other

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. CALCULATION: NOEC= 10e-0.803 log Kow+4.078 (Boeije et al 2006)

2. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: NOEC for long term toxicity to aquatic invertebrates (based on 21-day studies for training set)
- Unambiguous algorithm: NOEC= 10e-0.803 log Kow+4.078
- Defined domain of applicability: the training set includes alcohol ethoxylate mixtures (C9-11AE6, C12-13AE6.5, C12-15AE6, C12-15AE9, C13-15AE5 or C14-15AE7) and with the range of Log Kow is 3.65 to 5.91 (calculation based on Leo and Hansh, 1979). The training set data is summarised by Belanger et al. (2006) and Belanger and Dorn (2004). This data assessment of the Klimisch scores has been presented in the HERA document (HERA, 2009).
- Appropriate measures of goodness-of-fit and robustness and predictivity: For each studied ecotoxicity endpoint, the SSE for each QSAR model
was minimized by optimizing the slope and intercept parameters. The Microsoft Excel Solver routine (GRG2 optimization) (Excel 2000, Microsoft Corp., 1999) was used for this numerical procedure. The resulting SSE could be compared with the SSE obtained with the existing QSARs, to compare the goodness of fit with the underlying data.
- Mechanistic interpretation: based on nonspecific membrane disruption being the mode of action for all AE toxicity, which means that toxicity is related to the hydrophobicity and thus the Kow of the specific AE homologue .

3. APPLICABILITY DOMAIN
- Descriptor domain: log kow of 5.3 (predicted using Episuite which is based on Leo and Hansch calculation). It is difficult to get accurate results for experimental determinations of Log Pow of surfactants.
- Structural and mechanistic domains: C11-15AE3
- Similarity with analogues in the training set: the log Kow is in the middle of the training set range and structurally it has bigger distribution of the alkyl chain length with a shorter ethoxylated chain.
- Other considerations (as appropriate):Although toxicity was found to decrease with increasing ethylene oxide chain length, secondary attachments of the alkyl group were reported to be less chronically toxic than linear primary AE.

4. ADEQUACY OF THE RESULT
The QSAR fitting results described in the Boeije et al (2006) paper show that the deviation of the QSAR predictions from the measurements is less than a factor of 3, which is similar to the normal experimental variability in different ecotoxicological studies (see the table comparing measured and predicted long term EC50 and NOEC outcomes for D.Magna exposed to AE).

Principles of method if other than guideline:

- Principle of test: A new QSAR technique for complex substances, which interprets the mixture toxicity with regard to the‘‘ethoxymers’’ distribution (i.e., the individual AE components) rather than the average structure, was developed (Boeije et al, 2006) using the Log Kow.
- Parameters analysed / observed: NOEC for sediment toxicity based on Chronic Daphnia QSAR

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.2 mg/L

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: Daphnia Magna

Remarks:

QSAR calculation according to Boeije et al (2006)

Validity criteria fulfilled:

yes

Conclusions:

Based on the similar sensitivity of the sediment dwelling organisms compare with Daphnia magna, the sediment toxicity NOEC for softanol 30 was calculated as 0.20 mg/L using a 21-day chronic Daphnia QSAR for aquatic invertebrates developped by Boeije et al (2006).

Description of key information

The Daphnia Magna chronic endpoint for Softanol 30 (NOEC= 0.20 mg/L) is considered an appropriate chronic endpoint for Softanol 30 to sediment.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

28.1 mg/kg sediment dw

EC10, LC10 or NOEC for marine water sediment:

2.81 mg/kg sediment dw

Additional information

To determine the PNEC sediment for softanol 30, the aquatic PNEC derived from the chronic Daphnia magna QSAR was used with the equilibrium partioning method. The Daphnia Magna chronic endpoint for Softanol 30 (NOEC= 0.20 mg/L) is considered an appropriate chronic endpoint for Softanol 30 to sediment.

Using the equilibrium partitioning method is acceptable for chemicals with a log Kow between 3 and 6.

It should also be noted that Softanol 30 is readily biodegradable and there is no direct in-put of Softanol 30 into sediment making the proposal above conservative.