Potassium hexadecyl hydrogen phosphate

Endpoint summary

Additional information

Toxicity to fish

The study was performed in order to evaluate the toxic potential of potassium hexadecyl hydrogen phosphate towards freshwater fish. The study was conducted as limit test in accordance with OECD TG 203 and Regulation (EC) No 440/2008 method C.1. Seven juvenile rainbow trout were exposed in a static test for 96 hours to test water containing the test item at the concentration of nominal 100 mg test item/L. As the test item is poorly water soluble, the “water-accommodated fraction” (WAF) was tested. Therefore, a stock suspension of 100 mg test item/L was prepared. The stock suspension was stirred for 24 hours to dissolve as much test item as possible. Then, the undissolved test item was separated by filtration. The test media were prepared just before introduction of the test fish. In the control and the only test concentration of nominal 100 mg test item/L, all fish survived until the end of the experiment and showed no sublethal effects during the exposure time. The pH and the oxygen values were in normal ranges. The 96-h LC50 was determined at greater than 100 mg/L and the 96-h LC0 was 100 mg/L.

Toxicity to aquatic invertebrates

The purpose of this study was to evaluate the influence of the test item potassium hexadecyl hydrogen phosphate on the mobility of Daphnia magna according to OECD TG 202 and Regulation (EC) No 440/2008 method C.2. The test was performed as static limit test. Young daphnids were exposed 48 hours to test water containing the test item at the concentration of nominal 100 mg test item/L. This limit test was performed in compliance with the test guidelines to demonstrate that the test item has no toxic effect on daphnids up to at least this concentration.

 

This study was conducted using two treatment groups: one control and a filtrate of a supersaturated stock suspension of nominal 100 mg/L was tested (no concentrations above the solubility limit of the test item in the used test water were tested to avoid physical effects of undissolved test item onto the daphnids). Each treatment group contained 20 individuals. The mobility of the daphnids was determined in a static 48-hour test by visual observation after 24 and 48 hours. The collected samples analysed via LC-MS/MS-method. As the solubility of the test item in aquatic test media is very low, the concentrations of dissolved test item were below the Limit of Detection (0.2 µg test item/L). However, all reported results refer to nominal loading rate. The EC50 for the reference substance potassium dichromate was determined to be 0.706 mg/L. All validation criteria according to OECD TG 202 were met. The 48-hour NOEC was determined to be 100 mg test item/L (nominal). The 48-hour EC50 value was determined to be greater than 100 mg test item/L (nominal). Thus, no toxic effects on daphnia magna were observed up to the water solubility of the test item.

 

Toxicity to aquatic algae and cyanobacteria

The purpose of this test was to determine the inhibitory effect of the test item potassium hexadecyl hydrogen phosphate on the growth of the freshwater green algae Pseudokirchneriella subcapitata according to OECD TG 201 and Regulation (EC) No 440/2008 method C.3. The test was performed as static limit test. Exponentially growing cultures of this unicellular green algal species were exposed to one concentration of the test item under defined conditions. The inhibition of growth in relation to control cultures was determined over a test period of 72 hours, and thus over several algal generations.

Test concentrations were prepared by appropriate diluting of a stock solution. Based upon the results from the preliminary experiment, nominal concentrations of 100 mg/L were investigated in the main study. As the solubility of the test item in aquatic test media is very low, the concentrations of dissolved test item were below the Limit of Detection (0.7 µg test item/L). However, all reported results refer to nominal loading rate.

The 72-hour NOEC was determined to be at least the filtrate of nominal 100 mg test item/L (nominal). The NOEC might even be higher than this concentration, but concentrations in excess of nominal 100 mg test item/L. The 72-hour LOEC and the 72-hour EC50 were clearly higher than the filtrate of nominal 100 mg test item/L (nominal). These values could not be quantified due to the absence of toxicity of the test item up to the filtrate of nominal 100 mg test item/L (nominal).

The 72-h EC50 value based on growth rate was determined to be greater than 100 mg/L and based on yield was determined to be greater than 100 mg/L. The 72-h EC10 value based on growth rate was determined to be greater than 100 mg/L and based on yield was determined to be greater than 100 mg/L. The overall NOEC was determined to be greater than 100 mg/L. The results are based on the nominal concentrations.

Toxicity to microorganism

The influence of the test item potassium hexadecyl hydrogen phosphate on the activity of activated sludge was evaluated by measuring the respiration rate under defined conditions according to EU Method C.11 and OECD Guideline 209. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of one concentration of the test item, 100 mg/L (limit test) after an incubation period of 3 hours. 6 controls (tap water, synthetic sewage and inoculum, but without addition of the test item) were tested in parallel and a reference item 3,5-dichlorophenol was tested at the nominal test concentrations of 3.2, 10 and 32 mg/L under otherwise identical test conditions.

The respiration rates of the activated sludge treated with the test item at a concentrations of 100 mg/L differed by 10.2 % from control. The respiration rate of the activated sludge to potassium hexadecyl hydrogen phosphate at the rate of 100 mg/L was not statistically significant reduced when compared to the control. The determined NOEC was above 100 mg/L.

The positive control 3,5-Dichlorophenol was tested in the same way as the test item. The 3-hour EC50 was found to be 2.5 mg/L, thus, laying in the range of 2 - 25 mg/L recommended by the test guidelines. The result confirms the suitability of the activated sludge used.