2-ethylhexanoic acid, zirconium salt

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study according to OECD and GLP guidelines

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

During the in-life phase of the definitive study, one water sample (alternating between replicates A and B) from each treatment level and the control solution was collected at 0 hour (test initiation), 24 hours and 48 hours (test termination) for determination of test substance concentration. Samples were collected from the approximate midpoint of the test vessel by pipet.

Details on test solutions:

The dilution water source used during the definitive test was from a similar source as the water in the daphnid cultures and was characterized as having a total hardness and a total alkalinity (as CaCO3) range of 18 to 32 mg/L and 18 to 30 mg/L, respectively, a specific conductivity range of 60 to 80 µmhos/cm and a pH range of 7.2 to 7.6. Representative samples of the dilution water source were analyzed for the presence of pesticides, PCBs
and toxic metals by GeoLabs, Inc., Braintree, Massachusetts. None of these compounds have been detected at concentrations that are considered toxic in any of the water samples analyzed, in agreement with ASTM (2002) standard practice. A representative sample of the dilution water was analyzed for total organic carbon (TOC) concentration. The TOC concentration of the dilution water was 0.37 mg/L for the month of November 2006.
Several species of daphnids are cultured in water from the same source as the dilution water utilized in this study and have successfully survived and reproduced over multiple generations. The acceptable performance of the daphnid cultures, in combination with the previously mentioned analyses, confirmed the acceptability of this dilution water for bioassays.

A 100 mg/L diluter stock solution was prepared daily by adding 4.5 mL of acetone (CAS No. 67-64-1) to 4.4850 to 4.5150 g of zirconium 2-ethylhexanoate and gently mixing with a spatula. The slurry was transferred to 45 L of dilution water and mixed overnight. Following a one-hour settling period, a small to moderate amount of oily residue and undissolved test substance was observed. The water soluble portion of the stock solution
was pumped over to a diluter stock tank. The resulting diluter stock solution was observed to be clear and colorless.
In addition, a 0.51 mL/mL solvent stock solution was prepared by placing 13 mL of acetone in a 25-mL volumetric flask and bringing it to volume with distilled water. This solution was observed to be clear and colorless.

The 100 mg/L diluter stock solution was pumped into a pre-dilution mixing chamber which was calibrated to deliver 0.390 L of toxicant per cycle. The concentration of zirconium 2-ethylhexanoate in the solution contained within the mixing chamber was equivalent to that of the highest nominal test concentration (100 mg/L, equivalent to 13 mg Zr/L) and was proportionally diluted (50%) to produce the remaining nominal test concentrations (50, 25, 13 and 6.3 mg/L, equivalent to 6.6, 3.3, 1.6 and 0.82 mg Zr/L, respectively)

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISMS
- Age: < 24 hrs
- Source: Springborn Smithers culture facility

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

18 to 32 mg CaCO3/L

Test temperature:

19-21 °C

pH:

7.2-7.6

Nominal and measured concentrations:

- Nominal: 6.3, 13, 25, 50 and 100 mg zirconium 2-ethylhexanoate/L (= equivalent to 0.82, 1.6, 3.3, 6.6 and 13 mg Zr/L)
- Measured (dissolved): 0.02, 0.024, 0.023, 0.083, 0.17 mg zirconium 2-ethylhexanoate/L

Details on test conditions:

- Photoperiod: 16 hrs light / 8 hrs dark

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

mortality

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.17 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mortality

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.17 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mortality

Details on results:

Since no concentration tested resulted in > 50% immobilization, the 48 hrs EC50 was empirically estimated to be > 0.17 mg zirconium 2-ethylhexanoate/L

Validity criteria fulfilled:

yes

Conclusions:

No effect was observed at the highest tested nominal concentration (100 mg/L, corresponding to 0.023 mg dissolved Zr/L).

Description of key information

A reliable GLP-conform study (Klimisch 1) is available for the effect of 2-ethylhexanoic acid, zirconium salt on the immobilisation of Daphnia magna, according to the OECD 202 guideline. No effect was observed at the highest tested nominal concentration (100 mg/L, corresponding to 0.023 mg dissolved Zr/L).