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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material: 85% w/w 2,6-dimethyl-4-heptanone and 15% w/w 4,6-dimethyl-2-heptanone
(Diisobutyl Ketone)
- Physical state: transparent colorless liquid
- Analytical purity: 91.4%
- Lot/batch No.: SL3055T643
Analytical monitoring:
yes
Details on sampling:
- Sampled on: day 0, 1 and 2
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A stock solution of 200 mg/L was prepared by adding 542 µL DIBK to 2 L of Adjusted Laboratory Dilution Water (ALDW)
- Controls: ALDW without test substance
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Source: In-house cultures initially obtained from New England Bioassay, Inc., Manchester, Connecticut
- Age at study initiation (mean and range, SD): < 24h
Test type:
semi-static
Water media type:
freshwater
Total exposure duration:
48 h
Hardness:
148 - 156 mg CaCO3/L
Test temperature:
19 - 21°C
pH:
7.5 - 7.7
Dissolved oxygen:
7.7 - 8.7 mg/L
Nominal and measured concentrations:
Nominal concentrations: control, 4.67 - 7.78 - 13.0 - 21.6 - 36.0 - 60.0 mg/L
Measured concentrations: less than quantification limit of 0.911 mg/L (control) - 3.15 - 5.53 - 9.66 - 15.9 - 26.6 - 55.6 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: glass serum bottles
- Type: closed (sealed with an aluminium seal, containing a Teflon-lined rubber septa)
- Material, fill volume: glass, approx. 160 mL of total volume (void of headspace)
- Renewal rate of test solution: on day 1
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Obtained from the upper Saginaw Bay of Lake Huron off Whitestone Point. Before use in the laboratory, the water was sand-filtered, pH-adjusted with gaseous CO2, carbon-filtered, and UV-irradiated. The daphnid water was prepared by adjusting laboratory water to a hardness of about 170 mg/L as CaCO3 before autoclaving. Afterwards the water was autoclaved at 121°C and 18 psi for 30 min, cooled and aerated for approx. 24h.
- Total organic carbon: 1040 µg/L
- Pesticides: below detection limit
- Intervals of water quality measurement: weekly


OTHER TEST CONDITIONS
- Photoperiod: 16:8 hours
- Light intensity: 2050 +/- 350 lux


EFFECT PARAMETERS MEASURED: immobility


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.66
- Range finding study
- Test concentrations: control - 2.50 - 5.00 - 25.0 - 50.0 - 250 - 500 mg/L
- Results used to determine the conditions for the definitive study: 100% immobility at test concentrations of 500 - 250 - 50 mg/L; 20% immobility at test concentrations of 5.00 mg/L; no immobility was observed in the remaining test concentrations.
Reference substance (positive control):
no
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
55.6 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
37.2 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 31.3 - 45.2 mg/L
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
15.9 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Reported statistics and error estimates:
An appropriate U.S. EPA computer program was used to calculate the 24- and 48h EC50 values and corresponding 95% confidence intervals. The Probit Program and the Trimmed Spearman-Karber (TSK) Program were available.

The test exhibited a 48h EC50 of 37.2 mg/L and a 48h NOEC of 15.9 mg/L. The test concentrations are based on the mean measured concentrations because the measured test concentrations in the test vessels ranged from 59.4 - 92.3% (day 0), 55.0 - 93.7% (day 1), 73.9 - 89.7% (day 2). The lower percent of target concentrations were likely due to the volatility of the test substance.

Validity criteria fulfilled:
yes
Executive summary:

The acute toxicity of 2,6 -dimethylheptan-4 -one (diisobutyl ketone or DIBK) to the cladoceran, Daphnia magna, was evaluated following OECD guidelines (OECD 202) over a 48-hour exposure period. These data were used to calculate 24 -, and 48 -hour EC50 values and a 48-hour NOEC. The test exhibited a 48h EC50 of 37.2 mg/L and a 48h NOEC of 15.9 mg/L. The test concentrations are based on the mean measured concentrations because the measured test concentrations in the test vessels ranged from 59.4 - 92.3% (day 0), 55.0 - 93.7% (day 1), 73.9 - 89.7% (day 2). The lower percent of target concentrations were likely due to the volatility of the test substance.

Description of key information

A 48-hour static acute test evaluated the toxicity of DIBK to the cladoceran, Daphnia magna.  The test followed OECD 202 and meet GLP

requirements.  The reported 48-hour EC50 value was 37.2  mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
37.2 mg/L

Additional information

Two acute toxicity studies were available for 2,6-dimethylheptan-4-one (also known as diisobutyl ketone or DIBK) exposed to the freshwater cladoceran, Daphnia magna. A 2005 GLP study evaluated the toxicity of DIBK, followed OECD guidelines (OECD 203) and was rated a Klimisch score of 1, therefore it was selected as the Key study. The reported 48-hour EC50 value was 37.2 mg/L. An acute toxicity study, rated a Klimsch score of 2, was included as a supporting study. This supporting study was conducted prior to GLP requirements and followed guidelines outlined in Standard Methods. This supporting study reported a 48-hour EC50 value of 164 mg/L.