Phosphoric Acid, linear and branched Octyl Esters

Endpoint summary

Description of key information

Short-term toxicity to fish:

Oncorhynchus mykiss; OECD TG 203; read-across.

96-h LL50 value of greater than 100 mg/L loading rate WAF

Short-term toxicity to aquatic invertebrates:

Daphnia magna; OECD TG 202.

48-h EC50 > 5.62 mg/L (measured) (100 mg/L nominal loading rate WAF)

48-h NOEC = 5.62 mg/L (measured) (100 mg/L nominal loading rate WAF)

Toxicity to aquatic algae:

Pseudokirchneriella subcapitata; OECD TG 201

Results based on initial nominal loading rates (WAFs):

72 -h ErL50 > 100 mg/L; 72 -h EγL50 = 37.8 mg/L; 72 -h EbL50 = 36.51 mg/L

72 -h NOErLR = 12.5 mg/L; 72 -h NOEγLR = 6.25 mg/L; 72 -h NOEbLR = 6.25 mg/L

Results based on initial measured concentrations:

72 -h ErC50 > 28.92 mg/L; 72 -h EγC50 = 15.70 mg/L; 72 -h EbC50 = 15.29 mg/L

72 -h NOErC = 6.53 mg/L; 72 -h NOEγC = 3.71 mg/L; 72 -h NOEbC = 3.71 mg/L

Additional information

Short-term toxicity to fish:

No study is available for Phosphoric acid, C8-12 (even numbered) linear alkyl esters. Results are read across from an OECD TG 203 study performed on the 2-ethylhexyl- analogue. In this study, groups of 7 rainbow trout (Oncorhynchus mykiss) were exposed, in groups of seven, to a Water Accommodated Fraction (WAF) of the test item, at a single nominal loading rate of 100 mg/l for a period of 96 hours under semi-static test conditions. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours. The 96-h LL50 based on nominal loading rates was > 100 mg/l loading rate WAF and correspondingly the No Observed Effect Loading rate was 100 mg/l loading rate WAF.

Short-term toxicity to aquatic invertebrates:

Acute toxicity of Phosphoric acid, C8-12 (even numbered) linear alkyl esters on Daphnia magna was assessed in an Acute immobilisation test, over an exposure period of 48 hours in a static test system (OECD TG 202). Because no toxic response was observed during the preliminary range-finding test, a Limit Test was carried out using only one test concentration at the solubility level of the test item (100 mg/L nominal loading rate WAF) and one control group in the definitive test.

The test concentration was analytically determined at the start and at the end of the experiment. Measured concentration was 4.83 mg/L at the start and 6.55 mg/L at the end of the experiment, thus the corresponding measured geometric mean test item concentration was 5.62 mg/L. The biological results are based on the measured geometric mean test item concentration.

Twenty animals, divided into four groups (glass beaker) of five animals each were used at the test concentration and for the control.

All validity criteria were met during this study.

Under the conditions of this Daphnia magna acute immobilisation study the observed endpoints for the effect of Phosphoric acid, C8-12 (even numbered) alkyl esters were the followings:

The 24h and 48h EC50 value: > 5.62 mg/L (measured)

The 48h EC100 value: > 5.62 mg/L (measured)

The 48h No-Observed Effect Concentration (NOEC): 5.62 mg/L (measured)

The 48h Lowest Observed Effect Concentration (LOEC): > 5.62 mg/L (measured)

Toxicity to aquatic algae:

The effect of the test item was assessed on algal growth using the unicellular green alga Pseudokirchneriella subcapitata (Selenastrum capricornutum), over an exposure period of 72 hours (OECD TG 201).

A significant toxic response was observed during the preliminary range-finding test, therefore five test concentrations in a geometric series with a separation factor of 2.0 and one untreated control were tested in the main experiment.

The concentrations of test item used in the main experiment were: 6.25, 12.5, 25.0, 50.0 and 100.0 mg/L nominal loading rates WAFs. Test concentrations were analytically determined at the start of the test and at 24 hour intervals thereafter in order to better define loss of the test substance during the exposure period.

The test design included three replicates at each test concentration and six replicates for the untreated controls. There was an additional replicate without algae at each test concentration level for further analytical measurements (0, 24, 48 and 72 hours) in order to distinguish degradation and adsorption of the test item to algae.

According to the relevant guideline (OECD 201) disappearance of the test substance from solution by absorption to the increasing algal biomass does not mean that it is lost from the test system. When the result of the test was analysed, it was checked whether a decrease in concentration of the test substance in the course of the test was accompanied by a decrease in growth inhibition.

The corresponding measured geometric mean test item concentrations were: 1.78; 2.02; 8.95; 18.33 and 25.38 mg/L in presence of algae (more details are given in 4.2.). In addition, results of the analytical measurements of samples in absence of algae showed measured geometric mean test item concentrations of 3.46; 6.15; 11.99; 18.18 and 24.79 mg/L for the nominal concentrations of 6.25, 12.5, 25.0, 50.0 and 100.0 mg/L nominal loading rate WAFs respectively (more details are given in 4.2.).

However based on the section-by-section average specific growth rates, it is indicating that a decrease of concentration of the test item was not clearly accompanied by a decrease in growth inhibition. Based on these results most probably the test item is indeed absorbed to the increasing algal biomass, and should not be considered as lost from the test system.

Therefore it is recommended to express the EL50/EC50 and NOELR/NOEC//LOELR/LOEC values in the initial test item concentrations (nominal or measured) and not in the mean measured concentrations from the algae containing samples, thus biological results are related to the initial nominal loading rates (WAFs) and initial measured test item concentrations.

Results based on initial nominal loading rates (WAFs):

72 -h ErL50 > 100 mg/L; 72 -h EγL50 = 37.8 mg/L; 72 -h EbL50 = 36.51 mg/L

72 -h NOErLR = 12.5 mg/L; 72 -h NOEγLR = 6.25 mg/L; 72 -h NOEbLR = 6.25 mg/L

Results based on initial measured concentrations:

72 -h ErC50 > 28.92 mg/L; 72 -h EγC50 = 15.70 mg/L; 72 -h EbC50 = 15.29 mg/L

72 -h NOErC = 6.53 mg/L; 72 -h NOEγC = 3.71 mg/L; 72 -h NOEbC = 3.71 mg/L