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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
The study was conducted between 22 April 2014 and 13 June 2014.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
Temperature during the test varied by more than 2°C. The study integrity was not adversely affected by this deviation since the temperature was kept within the optimum range of 18-22°C & the daphnids were not affected by the slight variation of 2.3°C.
Qualifier:
according to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Qualifier:
according to guideline
Guideline:
ISO 6341 (Water quality - Determination of the Inhibition of the Mobility of Daphnia magna Straus (Cladocera, Crustacea))
GLP compliance:
yes
Specific details on test material used for the study:
Description: Yellow viscous liquid
Batch: SC00010629
Purity/Composition: UVCB substance
Analytical monitoring:
yes
Details on sampling:
Samples for Total Organic Carbon (TOC) analysis were taken from all test concentrations and the control at 0h and 48h. Reserve samples were taken at each sampling point.
Vehicle:
no
Details on test solutions:
The test item was prepared as a Water Accommodated Fraction (WAF). Preparation of test solutions was performed under dimmed light for both the combined limit/range-finding test and the final test. No correction was made for the purity/composition of the test substance.
All test solutions were prepared separately. Various loading rates of the test substance were added to test medium and magnetically stirred for one day.The resulting aqueous mixtures for the combined limit/range-finding test were not left to stabilize. The clear and colourless WAFs were directly taken out by siphoning. The aqueous mixtures for the final test were left to stabilize for one hour where after the clear and colourless WAFs were taken out by siphoning.
WAFs prepared at loading rates of 10, 22, 46, 100 and 220 mg/l.
Test organisms (species):
Daphnia magna
Details on test organisms:
Test organisms: Daphnia magna, at least third generation, obtained by acyclical parthenogenesis
Source: In-house laboratory culture
Validity of batch: Daphnids originated from healthy stock showing no signs of mortality.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
Not applicable
Hardness:
180 mg/l expressed as CaCO3
Test temperature:
Temperature was kept within the optimum range of 18-22°C. Daphnids were not affected by this slight variation of 2.3°C.
pH:
7.7 - 7.9
Dissolved oxygen:
8.7 - 9.2 mg/L
Salinity:
Not applicable
Nominal and measured concentrations:
WAFs were prepared at loading rates of 10, 22, 46, 100 and 220 mg/l.
Details on test conditions:
Tests were conducted in adjusted ISO medium. Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to a control and to WAFs prepared at loading rates of 10, 22, 46, 100 and 220 mg/l. Each test vessel contained 5 daphnids and 80 mL test solution. The total exposure period was 48 hours. There was no illumination during testing and daphnids were not fed. Immobility was measured at 24 and 48 hours after test initiation. Temperature was measured constantly in a temperature control vessel, and dissolved oxygen and pH were measured in all vessels at the start and end of the test.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
48 h
Dose descriptor:
NOELR
Effect conc.:
46 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
67 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
24 h
Dose descriptor:
EL50
Effect conc.:
77 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
In the final test, after 48 hours of exposure all daphnids exposed to the two highest test concentrations were immobilized. This was not in agreement with the results of the combined limit/range-finding test (see "Any other information on materials and methods" above) but can be explained by the fact that the final test was performed in the dark. Probably, part(s) of the test substance that causes the toxicity degraded during the combined limit/range-finding test due to photosensitivity. The pH and dissolved oxygen remained within the limits prescribed by the protocol (pH: 6.0-8.5, not varying by more than 1.5 units; oxygen: >3 mg/l at the end of the test).
Results with reference substance (positive control):
The 48h-EC50 was 0.41 mg/l with a 95% confidence interval between 0.36 and 0.47 mg/l. This is within the range of the expected
48h-EC50 for this reference substance i.e. between 0.3 and 1.0 mg/l. Thus, the sensitivity of the daphnia was within the range determined with the historical data collected at the test facility.
Reported statistics and error estimates:
The 24 and 48h-EL50-value was calculated from the probits of the percentages of affected daphnids and the logarithms of the corresponding test substance loading rates using the maximum likelihood estimation method. No confidence intervals could be given as the calculations were based on two concentrations.
ToxRat Professional v 2.10.05 (ToxRat Solutions® GmbH, Germany) was used to perform the analyses.

Table 1: Effect parameters

Parameter

Loading rate1Aurantiol Pure (mg/L)

48h-NOELR

46

24h-EL50

77

48h-EL50

67

1 WAF prepared at a given loading rate

Validity criteria fulfilled:
yes
Conclusions:
The 48h-EL50 was for Daphnia magna 67 mg/l. The 48h-NOELR for effects on mobility was 46 mg/l.
Executive summary:

The acute toxicity of Aurantiol Pure to Daphnia magna was tested according to OECD guideline 202. Information provided by the Sponsor indicated that the test item is a complex mixture (UVCB) composed of constituents with different water solubility. Therefore the test item was prepared as a Water Accommodated Fraction (WAF). Various loading rates of the test substance were added to test medium and magnetically stirred for one day. The resulting aqueous mixtures were left to stabilize for one hour where after the clear and colourless Water Accommodated Fractions (WAFs) were taken out by siphoning. The WAFs were used for testing. Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to a control and to WAFs prepared at loading rates of 10, 22, 46, 100 and 220 mg/l. The total exposure period was 48 hours and samples for Total Organic Carbon (TOC) analysis were taken at the start and at the end of the test.

Given that toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole, the effect parameters were based on nominal loading rates. The study met the acceptability criteria prescribed by the protocol and was considered valid. The 48h-EL50 was 67 mg/l. The 48h-NOELR for effects on mobility was 46 mg/l.

Description of key information

For the purposes of the environmental risk assessment, two assessment entities have been defined (Hydroxycitronellal and Methyl Anthranilate). The most sensitive species for these two substances was identified as green algae and fish respectively (see aquatic toxicity endpoint summary). Thus data from these endpoints has been used in derivation of PNECaquatic (see respective endpoint records for details).

Key value for chemical safety assessment

Additional information

For the purpose of classification and labelling, data on the whole substance has been considered. A study was performed to assess the acute toxicity of the test item to Daphnia magna. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphnia sp., Acute Immobilisation Test" referenced as Method C.2 of Commission Regulation (EC) No. 440/2008. Since the substance is a complex mixture (UVCB) composed of constituents with different water solubility, the test item was prepared as a Water Accommodated Fraction (WAF). Various loading rates of the test substance were added to test medium and magnetically stirred for one day. The resulting aqueous mixtures were left to stabilize for one hour where after the clear and colourless Water Accommodated Fractions (WAFs) were taken out by siphoning. The WAFs were used for testing. Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to a control and to WAFs prepared at loading rates of 10, 22, 46, 100 and 220 mg/l. The total exposure period was 48 hours and samples for Total Organic Carbon (TOC) analysis were taken at the start and at the end of the test.

The concentration of the test substance in the aquatic samples was calculated using the TOC content of pure test substance, which had been experimentally determined to be 68.20%. A correction was made for the measured amount of TOC in the control. The initial concentrations in samples taken from the WAFs prepared at loading rates of 46, 100 and 220 mg/l were calculated to be 41, 81 and 165 mg/l. These concentrations remained stable during the exposure period (95-99% of initial). The concentrations for the two lowest WAFs were not determined since these were below the No Observed Effect Loading Rate (NOELR), i.e. the highest loading rate tested at which no immobilisation was recorded.

Given that toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole, the effect parameters were based on nominal loading rates. The study met the acceptability criteria prescribed by the protocol and was considered valid. The 48h-EL50 was 67 mg/l. The 48h-NOELR for effects on mobility was 46 mg/l.