Tris(2,4-ditert-butylphenyl) phosphite

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study conducted in compliance with GLP regulations.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Analytical determinations of the test substance concentrations were conducted with freshly prepared loadings on day 2, 9, and 14 of the exposure period and at the renewal time with the old loadings at day 5, 12 and 16, respectively. The analysis was conducted in two pooled samples, each containing the test solutions of five individual test vessels.

Vehicle:

yes

Details on test solutions:

Since the test item is a substance that is only partially soluble, the water accommodated fraction (WAF) approach was used. The test loading was prepared by adding the respective amount of a tetrahydrofuran (THF) stock solution to empty glass vessels. After complete evaporation of the solvent, the aerated daphnia medium was added, moderately stirred for 144-168 h, followed by filtration (MILLIPORE AP15 glass fiber filter). The resulting water soluble (WSF) fraction was used in the test. The duration of the stirring period was based on the non-GLP pretests.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Test organism: Daphnia magna (Straus, 1820)
- Age at test start: Less than 24 h
- Breeding: Parental and young Daphnia held in 4 L glass aquaria (3 L medium) at 20 ± 2 °C
- Illumination: 16 h per day
- Medium: Continuously aerated Elendt M4 medium; prepared with deionised water (conductivity <1.5 µS/cm)
- Feed: Suspension of Desmodesmus subspicatus in Elendt M4 medium with an optical density OD680 of about 15 units
- Frequency of feeding: 400 μl per Daphnia per day, except on weekends

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

21 d

Hardness:

Total hardness (as sum of Ca and Mg): 2.52 mmol/L
Carbonate hardness: 0.32 mmol/L

Test temperature:

20±2 °C (temperature-controlled room)

pH:

The pH in the blank control varied by 1.4 units from 6.6 to 8.0
The pH in the test vessels varied by 1.3 units from 6.6 to 7.9

Dissolved oxygen:

The dissolved oxygen concentration was ≥5.6 mg O2/L (5.3 - 9.1 mg O2/L)

Nominal and measured concentrations:

Test concentration (Loading rate): 2.0 mg/L
Test concentration (measured): 1.42 µg/L (geometric mean)

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 ml Erlenmeyer flasks, sealed with glass stoppers, with 100 ml of test medium to minimize the headspace (closed system)
- Renewal rate of test solution: 3 renewal cycles per week
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Dilution water: Elendt M4 medium prepared with deionised water (conductivity <1.5 µS/cm)

OTHER TEST CONDITIONS
- Photoperiod: 16 h a day
- Light: white fluorescent tubes

RANGE-FINDING STUDY
- Test concentrations: 10 and 100 mg/L (loading rates)
- Test conditions: 3 replicates (0 mg/L) and 2 replicates (10, 100 mg/L), 20 daphnids per replicate.
- Results used to determine the conditions for the definitive study: after 48h 100 mg/L (loading rate) resulted in no immobilisation

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

>= 2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(loading rate of WAF)

Basis for effect:

reproduction

Details on results:

With respect to parental daphnids survival, no mortality was observed at the loading rate of 2 mg/L. In the blank control, one paternal daphnid died. No other detrimental effects were observed.
The first appearance of living offspring was observed between day 8 and 12 at the loading rate of 2.0 mg/L and in the blank control.

Results with reference substance (positive control):

The EC50 for the control of sensitivity for 24 h of exposure with potassium dichromate was estimated to be 0.8 mg/L (data from the most recent test on 7 December 2012). The resulting EC50 value of the reference item was within the recommended range of 0.6 - 2.1 mg/L according to OECD Guideline 202.

Validity criteria fulfilled:

yes

Conclusions:

The substance is with high probability not chronically harmful to aquatic invertebrates.

Description of key information

The substance is with high probability not chronically harmful to aquatic invertebrates.
No long-term effects occurred for Daphnia magna (OECD 211) in the range of water solubility; NOEL (21d) >= 2 mg/L (based on the Loading rate of a WAF)

Additional information

The long-term toxicity on aquatic invertebrates was investigated with the waterflea Daphnia magna, in a GLP guideline study according to OECD 211 [BMG, 2013].  Since the test item is a substance that is only partially soluble, the test solution was prepared as water accommodated fraction (WAF), with a loading rate of 2 mg/L. During the three weeks test duration a geometric mean concentration of 1.42 µg/L was measured.

The first appearance of living offspring was observed between day 8 and 12 at the loading rate of 2.0 mg/L and in the blank control. No effects on the offspring were determined during the 21 days test duration. Therefore, the no observed effect loading (NOEL) was >= 2.0 mg/L.