2,4,6-tri-tert-butylphenol

Short-term toxicity to aquatic invertebrates

Description of key information

The 48 h EC50 was determined to be >0.072 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.072 mg/L

Additional information

There are two studies available to address this endpoint, one key and one supporting.

 

In the key study, the acute toxicity of the test material to daphnia magna was investigated in a study conducted in accordance with the standardised guidelines OECD 202, EU Method C.2 and the Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23 under GLP conditions. The study was assigned a reliability score of 1 in line with the principles for assessing data quality as defined by Klimisch et al. (1997).

 A combined limit/range-finding test was performed. A Water Soluble Fraction (WSF) prepared at a loading rate of 100 mg/L was used as the highest concentration. The lower test concentrations were prepared by subsequent dilutions of the highest concentration in test medium. The final test solutions were all clear and colourless.

Twenty daphnids per group (5 per replicate, quadruplicate) were exposed to an untreated control and to an undiluted WSF in a limit test. In addition, ten daphnids per group (5 per replicate, duplicate) were exposed to solutions containing 1.0 and 10 % WSF, in the combined range-finding test. The total exposure period was 48 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test. The exposure vessels were closed airtight and the headspace was reduced to a minimum.

Samples taken from the limit concentration were analysed. The actual concentration measured at the start of the test was 0.072 mg/L. The measured concentration remained stable during the exposure (96 % of initial). Therefore, the effect parameters were expressed in terms of measured concentrations.

No effects were observed in any of the groups tested.

Under the conditions of this study, the 48 h EC50 exceeded a measured concentration of 0.072 mg/L, being considered the maximum solubility of the test material in medium.

 

In the supporting study, the toxicity of the test material to the daphnid was estimated using the ECOSAR model v1.11 (EPI Suite v4.11). The study was awarded a reliability score of 2 in line with the principles for assessing data quality as defined by Klimisch et al. (1997).

The structure-activity relationships (SARs) presented in this program are used to predict the aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the aquatic toxicity has been previously measured. Most SAR calculations in the ECOSAR Class Program are based upon the octanol/water partition coefficient (Kow). The toxicity of the test material to daphnids was estimated using the Phenols class of ECOSAR. The molecular weight of the test material is within the training set range.

The estimated 48 hour LC50 was 0.045 mg/L.