Bis(2-ethylhexyl) hydrogen phosphate

Short-term toxicity to fish

Description of key information

The most reliable experimentally determined 96h-LC50 value of bis(2-ethylhexyl) hydrogen phosphate was 30 mg/L on Salmo gairdneri.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

30 mg/L

Additional information

Three studies are available with regard to the acute toxicity of bis(2-ethylhexyl) hydrogen phosphate to fish.

Despite the fact that these studies are not documented satisfyingly, their scientific value appears sufficient for assessment. Especially since the toxicity data of all three studies reveal very similar 96h LC50 values lying within the same order of magnitude.

 

The most reliable study is a toxicity test performed with Salmo gairdneri (now Oncorhynchus mykiss) in a static test system at 15°C and 20°C. Although there was no guideline stated, the tests were performed under generally accepted scientific principles. Experiments were conducted with 10 animals at each concentration tested.

The pH was initially adjusted to 7.9. At 20°C a 96h-LC50 of 20 mg/l was obtained and at 15°C a 96h-LC50 of 30 mg/L was observed, both related to nominal concentrations. The recommended temperature for rainbow trout is 15°C according to OECD TG 203, therefore the 96h-LC50 value at 15°C is the preferred value for assessment. Effects resulting from the exposure conditions at 20°C cannot be excluded. Although no details on the amount of test concentrations were reported the study is considered as reliable and was therefore chosen as key study.

 

In another study, toxicity of bis(2-ethylhexyl) hydrogen phosphate towards fish was assessed in a toxicity range finding test under static conditions. Salmo gairdneri was exposed to several concentrations at 15°C for 96 h of exposure, which is in accordance with OECD TG 203. Due to the large size (15 - 25 g) of fish, only 4 fish were used at each test concentration. Analysis of test substance was carried out by spectrophotometric determinations of the total phosphorus content. A 96h-LC50 of 48–54mg/L based on measured concentrations was obtained in this test. Since this value lies well within the order of magnitude of the key study (30 mg/L) the study is considered as useful for assessment. However, based on methodological deficiencies (only 40% of the required number of test fish are used) the study was only used as supporting study.

 

Following the procedure of ISO/TC 147/SC5/WG3 (France: acute toxicity test; static) with 2 exceptions, the toxicity of bis(2-ethylhexyl) hydrogen phosphate towards Danio rerio was assessed. Only 5 juvenile zebrafish were exposed to bis(2-ethylhexyl) hydrogen phosphate at a temperature of 25°C and the exposure time was extended to 144h (6 days). Appropriate amounts (0-5.6 mL) of substance stock solutions were made up in acetone.

After evaporation of acetone just to dryness at room temperature, premade aerated Standard Reference Water was added to each flask. A solvent control (maximal amount of acetone evaporated just to dryness) and an ordinary control were included in the test procedure. A 144h-LC50 and a 96h-LC50 of > 56 mg/l were reported. The LC50 was above the highest concentration tested. Based on methodological deficiencies (only 50% of the required numbers of test fish are used) the study is scored as reliable with restrictions and is considered to be useful for assessment. The study is therefore used as a supporting study.