Registration Dossier

Ecotoxicological information

Long-term toxicity to aquatic invertebrates

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Reliable weight of evidence from both a surrogate substance and QSAR indicate that the chronic NOEC for ethoxypropanol in invertebrates will be > 100 mg/L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
100 mg/L

Additional information

There is no measured data available on this substance but there is measured data on a closely related substances and there is a reliable QSAR that can also be used and together these allow interpolation to be used to predict with some confidence the likely toxicity to invertebrates of this substance.

In a guideline and GLP study, the 21-day EC50 (reproduction) value for dipropylene glycol monoethyl ether based on nominal test concentrations was determined to be greater than 180 mg/l, given that  no significant differences (P ≥ 0.05) in terms of the number of young produced (total or per adult) were observed on days 7, 14, and 21.

US EPA ECOSAR software (v1.11) predicts the Chv (NOEC) for ethoxypropanol to be 150 mg/L, based on structure activity relationship models for neutral organic compounds. Estimates for the surrogate materials using the same QSAR were 300mg/l for methoxypropanol, 180mg/l for dipropylene glycol monoethyl ether, 71mg/ml for propylene glycol propyl ether and 34mg/l for propylene glycol butyl ether, suggesting that the model is consistent with and likely more conservative than experimental results. The mode of action of this substance is likely to be non-polar narcosis (see overall summary to chapter 6.1 for further information.) This means that toxicity is likely to be linked with the partition coefficient. This would suggest increasing toxicity with increasing length of the alkyl group and decreasing toxicity with increasing number of PO units in the molecule. This is reflected in the QSAR results and the measured values available are consistent with this trend. The QSAR can be considered highly reliable in predicting relative toxicity.

These results, coupled with the knowledge that the acute QSAR predictions overestimate toxicity by a factor of 2.5 to 5 on a weight of evidence approach indicate that the chronic EC50 for ethoxypropanol in daphnids is will be >=100 mg/L.

An extensive justification for read across is contained in the read across justification attached to chapter 13 of this dossier.