2,4,6-tri-tert-butylphenol

Short-term toxicity to fish

Description of key information

The 96 h LC50 in carp was determined to be >0.048 mg/L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

0.048 mg/L

Additional information

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

 

In the key study, the acute toxicity of the test material to carp was investigated in accordance with the standardised guidelines OECD 203, EU Method C.1 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).

Following an initial range-finding test, a full test was performed with Cyprinus carpio under semi-static conditions. The test material was not completely soluble in test medium at the loading rate initially prepared; therefore a Water Soluble Fraction (WSF) was prepared at a loading rate of 100 mg/L and 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. Test solutions were prepared daily.

Seven fish per group were exposed to an untreated control and solutions containing 10, 18, 32, 56 and 100 % WSF. The total exposure period was 96 hours. Test solutions were renewed on a daily basis. Samples for analytical confirmation of the exposure concentrations were taken at the start and at the end of the first and the last refreshment period.

The responses recorded in this test allowed for reliable determination of an LC50. No mortality was observed in any of the groups tested. In the 100 % WSF, at 96 hours one fish was observed to be immobile and 6 fish were observed to be hypoactive. Samples taken from the highest concentration were analysed; the average exposure concentration was calculated and corresponded to 0.048 mg/L.  

Under the conditions of this study, the 96 h LC50 exceeded an average exposure concentration of 0.048 mg/L, being considered the maximum soluble concentration in test medium.

Both of the supporting studies were assigned a reliability score of 2 in line with the principles for assessing data quality as defined by Klimisch et al. (1997).

The first supporting study, the toxicity of the test material to fish was estimated using the ECOSAR model v1.11 (EPI Suite v4.11).

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 fish was estimated using the Phenols class of ECOSAR. The molecular weight of the test material is within the training set range.

The estimated 96 hour LC50 was 0.021 mg/L.

 

In the second supporting study, the potential of the test material to cause acute toxicity to fish was investigated in a study conducted broadly in line with the standardised guideline OECD 203.

Following a range-finding test, the test material was administered to 10 Rainbow trout (Oncorhynchus mykiss) at a concentration of 0.10 mg/L in 1 % v/v Tween 80 – tetrahydrofuran for a period of 96 hours. Concurrent negative and solvent controls were each run with 10 fish.

No mortality was seen in either replicate of the treated fish, or in the control or solvent control.

Under the conditions of this study the LC50 was determined to be > 0.10 mg/L.