Hexadecyl dihydrogen phosphate

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

GLP compliance not specified

Justification for type of information:

The substance that has been tested for this end point is the potassium salt of the hexadecyl hydrogen phosphate. Once in solution, the potassium ion will dissociate from the substance leaving the hexadecyl hydrogen phosphate anion as the organic species of relevance for the effect on aquatic species, which is basically the substance being registered.
The potassium ion in solution is ubiquitous in aquatic systems and known not to be toxic at low levels. The pH of the mono constituent substance being registered, which is >= 80% hexadecyl hydrogen phosphate, is reported to be around 5.0, slightly lower than the K salt in solution. Both the K salt and the acid substance are of very low solubility. The aquatic test for alga recognised this issue and testing was carried out as per insoluble substances.
The similarity in substances and properties have been assessed and read-across is considered totally valid.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

not specified

Remarks:

The test report does not mention any reference to quality assurance or GLP

Specific details on test material used for the study:

No batch information given. ColaFax CPE-K was supplied for this test, presumably as the product that is marketed by the company.
The substance was a white powder. The material was stored in the dark at approximately 4 deg C

Analytical monitoring:

no

Vehicle:

yes

Remarks:

laboratory water

Details on test solutions:

The test article was reported to be readily soluble in water at all concentrations used in the study. Test concentrations were made by adding measured (mass) quantities of test article and diluting to known volumes with laboratory water. Acute endpoints were calculated on a nominal concentration basis (mg/L).
Test article concentrations ranged from 1210 mg/L to 8000 mg/L with a factor of 0. 6 from one concentration to the next lower concentration.
The comment from the test report referring to the substance being 'readily soluble' is in doubt considering all the other information that is known about the poor solubility of this substance.

Test organisms (species):

Daphnia pulex

Details on test organisms:

The test animals are cultured at approximately 24 deg C in laboratory water and are fed a unicellular green alga, Selenastrum capricornutum, and a digested combination of yeast, cereal leaves, and trout chow (YCT) daily. The light regimen is 16 hours light and 8 hours dark under wide spectrum fluorescent bulbs.
Organisms used in the definitive test were less than 24 hour old neonates spawned from adults held in laboratory water.
Organisms were not fed during the test

Test type:

static

Water media type:

freshwater

Remarks:

Dilution water used in all of the range finding and definitive bioassays was laboratory water. Alkalinity 91 mg/L as CaC03 Hardness 122 mg/L as CaC03 pH 7.6 Conductivity 250 micromho ' s/ cm Suspended solids <1 mg / L Dissolved solids 228 mg / L

Total exposure duration:

48 h

Test temperature:

24.8 - 25.6 deg C

pH:

7.1 - 7.6

Dissolved oxygen:

>80% saturation

Details on test conditions:

The definitive test consisted of six treatments: five test article concentrations, and one laboratory water control . Four replicates of each treatment with five test organisms in each replicate were used. Test chambers were 50 mL borosilicate glass beakers each filled with 30 mL of test solution. The toxicity test was conducted in an incubator under wide spectrum fluorescent lighting . Test temperature ranged from 24.8 to 25. 6 deg c (mean value- 25.3 deg C) . The pH of test solutions ranged from 7.6 in the test treatment with the lowest amount of test article to 7.1 in the test treatment that contained the highest amount of test article. Dissolved oxygen levels maintained >80% saturation in all test solutions throughout the test.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

Actual values from the test report suggest that the effect concentration was higher than 100 mg/l. However, no test method was used to determine the level of substance in solution, and it is known that the actual solublity of this substance is low, of the order of ~100 mg/l. Hence it is highly unlikely that the higher nominal levels of solublised substance in the dilution water were accurate. There may have been some undissolved substance in the system. In any event, no mortality of daphnia pulex was observed at a reported dosing of 1200 mg/l

Conclusions:

The substance showed no adverse effects on the test organisms at over the limit of reported water solubility when tested by WAF method.

Description of key information

The substance that has been tested for this end point is the potassium salt of the hexadecyl hydrogen phosphate. Once in solution, the potassium ion will dissociate from the substance leaving the hexadecyl hydrogen phosphate anion as the organic species of relevance for the effect on aquatic species, which is basically the substance being registered.

The potassium ion in solution is ubiquitous in aquatic systems and known not to be toxic at low levels. The pH of the mono constituent substance being registered, which is >= 80% hexadecyl hydrogen phosphate, is reported to be around 5.0, slightly lower than the K salt in solution. Both the K salt and the acid substance are of very low solubility. Testing was carried out as per insoluble substances.

The similarity in substances and properties have been assessed and read-across is considered valid.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L