Bis(2-ethylhexyl) hydrogen phosphate

Endpoint summary

Additional information

Assessing the aquatic toxicity of bis(2-ethylhexyl) hydrogen phosphate, no OECD guideline studies are available for fish or daphnia. The available tests reveal certain deficiencies in data reporting, but follow general scientific principles and are therefore rated as reliable with restrictions and considered as useful for assessment.

In combination the present studies provide sufficient evidence with regard to the properties of the substance concerning aquatic toxicity.

The most reliable and sensitive studies are taken into account for assessment. For algae, there is only one study on toxicity to aquatic plants available. The result of this study cannot be sufficiently validated and is therefore scored to be reliable with rertrictions only.

In order to draw a conclusion on toxicity towards aquatic plants for bis(2-ethylhexyl) hydrogen phosphate, read across with dibutyl hydrogen phosphate (CAS No. 107-66-4) is proposed. Dibutyl hydrogen phosphate and bis(2-ethylhexyl) hydrogen phosphate have very similar chemical structures and their main physico-chemical parameters (vapour pressure, water solubility, octanol/water partition coefficient, organic carbon partition coefficient and dissociation constant) are in the same range. Therefore a read across between these two substances to cover physico-chemical and ecotoxicological endpoints for bis(2-ethylhexyl) hydrogen phosphate seems to be justified.

More details regarding the read across justification are depicted in the annex of the Chemical Safety Report (CSR).

Fish (short-term)

In a static test system a 96h-LC50 of 30 mg/L at 15°C was determined for bis(2-ethylhexyl) hydrogen phosphate on rainbow trout (Salmo gairdneri) related to nominal concentration. There was no guideline stated but the test was conducted under generally accepted scientific principles.

Fish (long-term)

Embryo and larvae toxicity of bis(2-ethylhexyl) hydrogen phosphate was investigated on rainbow trout in a semi-static test system. A 48d-NOEC of 20.6 mg/L related to nominal concentrations was observed. The test was performed under generally accepted scientific principles referring to the U. S. EPA procedure. A further test with the same test design revealed a 10d-NOEC of 21 mg/L on zebrafish (Brachydanio rerio). Both studies were assessed as long-term toxicity as the fish were exposed at the most sensitive developmental stages.

Daphnia (short-term)

A 48h-LC50 of 60.7 mg/L related to nominal concentrations was observed on Daphnia magna under static test conditions. There was no guideline stated but the test was performed under generally accepted scientific principles.

Algae

As there are only few data available for bis(2-ethylhexyl) hydrogen phosphate, read across with dibutyl hydrogen phosphate (CAS No. 107-66-4) is proposed to cover this endpoint.

According to OECD TG 201 ' Alga, Growth Inhibition Test' the acute toxicity of dibutyl hydrogen phosphate to alga (Desmodesmus subspicatus) was tested. After 72 hours an ErC50 of >100 mg/L was received and a NOEC of 50 mg/L was calculated. The lowest concentration 3.1 mg/L slightly dropped below the 80% recovery limit during the 72-hour exposure period. This is considered as not significant, because the highest determined concentration remained stable over the exposure time and therefore all results are expressed in terms of nominal concentrations.

Microorganisms

To assess the toxicity of the substance to microorganisms a study was conducted according to the OECD TG 209. Bis(2-ethylhexyl) hydrogen phosphate showed 55.73 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L. An EC10 of 196 mg/L and an EC50 of 890 mg/L were obtained. The effect value related to nominal concentration, since no analytical monitoring was performed.