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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity 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:
- Concentrations: 0 - 9.33 - 15.6 - 25.9 - 43.2 - 72.0 - 120 mg/L
- Sampling method: Sampled on days 0, 2, and 4 of the study. Aliquots (2 mL) were collected and transferred to 4-dram vials for extraction.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Aquaria (two replicate aquaria per dose level) were replenished on a regular intermittent cycle with test solutions delivered from a flow-through proportional diluter, which was fortified from a feedstock of undiluted DIBK. The test material was a liquid with a purity of 91.4% and a specific gravity of 0.808. Based on this, during each cycle of the diluter,
0.877 mL of the feedstock was diluted with ~5.4 L of lab dilution water in the mixing chamber yielding a nominal concentration of 120 mg DIBK/L. This solution (undiluted becomes the top dose level) was then pumped into the cascading dilutor vessels, which resulted in five ~60 percent serial dilutions. The solutions were then dumped from the cascading dilutors into splitter cells, which equally dispersed the test solutions into the two replicate test vessels at each dose level. This resulted in nominal (target) concentrations of 120, 72.0, 43.2, 25.9, 15.6, and 9.33 mg DIBK/L-LDW, in addition to control water (LDW with no test material added and referred to as water control) being delivered with each cycle of the diluter. No evidence of incomplete dissolution of test material was observed in the diluter system or test vessels.
- Controls: LDW with no test material added
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
TEST ORGANISM
- Common name: rainbow trout
- Source: Obtained as juveniles from Thomas Fish Company, Anderson, California
- Age at study initiation (mean and range, SD): juveniles
- Length at study initiation (length definition, mean, range and SD): 4.7 +/- 0.3 cm
- Weight at study initiation (mean and range, SD): 0.805 +/- 0.124 g


ACCLIMATION
- Acclimation period: 14 days at 13 +/- 1°C and held without food for at least 48 hours before testing
- Type and amount of food: Aquatic Diet Number 1 (Lot #233796, Harlan-Teklad, Madison, Wisconsin)
- Feeding frequency: once daily
Test type:
flow-through
Water media type:
freshwater
Total exposure duration:
96 h
Hardness:
96 - 98 mg CaCO3/L
Test temperature:
12 - 14°C
pH:
7.1 - 7.4
Dissolved oxygen:
6.6 - 9.5 mg/L (64 - 92%)
Nominal and measured concentrations:
Nominal concentrations: control - 9.33 - 15.6 - 25.9 - 43.2 - 72.0 - 120 mg/L
Measured concentrations: The mean measured concentrations were less than the quantification limit of 0.95 mg/L in the controls and 8.08 - 13.6 - 23.1 - 38.9 - 63.0 - 109 mg/L in the treatment solutions
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass aquaria
- Type: covered with glass
- Material, size, fill volume: glass, 30x15.5x12,5 cm, approx. 3.7 L
- Aeration: yes
- Type of flow-through: proportional diluter
- Renewal rate of test solution: 0.985 L per cycle with an average of 76 cycles per day
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- Biomass loading rate: 1.1 g fish/L


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The laboratory dilution water (LDW) was obtained from the upper Saginaw Bay of Lake Huron near Whitestone Point and was limed and flocculated with ferric chloride. Before use the water was sand-filtered, pH-adjusted with gaseous CO2, carbon-filtered and UV-irradiated.
- Total organic carbon: 1040 µg/L
- Pesticides: below detection limit
- Alkalinity: 35 mg/L CaCO3
- Conductivity: 176 µmho/cm
- Intervals of water quality measurement: The LDW was monitored weekly (Alkalinity, conductivity, pH and hardness). Dissolved oxygen, pH and temperature were measured daily in the test vessels.


OTHER TEST CONDITIONS
- Photoperiod: 16-hours light/8-hours dark
- Light intensity: 684 - 894 lux


EFFECT PARAMETERS MEASURED: mortality and any behavioral or pathological effects were noted (observed every 24, 48, 72 an 96h)


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.66
- Range finding study
- Test concentrations: control - 14.2 - 23.7 - 39.4 - 65.7 - 110 - 183 mg/L
- Results used to determine the conditions for the definitive study: Mortality was observed in 20% of the fish at the 65.7 mg/L test level and 100% of the fish at the 110 and 183 mg/L test level. No sublethal effects and mortality were observed on the control and 14.2 mg/L test level. The 23.7 mg/L test level could not be evaluated due to a blockage of the diluter's water delivery cell.
Reference substance (positive control):
no
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
30 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 23.1 - 38.9 mg/L
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
30 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 23.1 - 38.9 mg/L
Duration:
72 h
Dose descriptor:
LC50
Effect conc.:
30 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 23.1 - 38.9 mg/L
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
30 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 23.1 - 38.9 mg/L
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
23.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
- Behavioural abnormalities: One fish at the 23.1 mg/L test level showed a partial loss of equilibrium following 24h of exposure
- Mortality of control: 0%
Reported statistics and error estimates:
The LC50 values were calculated by the U.S. EPA Trimmed Spearman-Karber Program

The test exhibited a 96h LC50 of 30 mg/L based on the mean measured concentrations. The study average recovery values ranged from 86.6 - 90.8% of target concentrations. All validity criteria stated in the OECD guideline 203 were met.

Validity criteria fulfilled:
yes
Conclusions:
The 24-, 48-, 72-, and 96-hour LC50 values were all 30.0 mg/L, with a 95% confidence interval of 23.1-38.9 mg/L. The 96-hour NOEC was 23.1 mg/l.
Executive summary:

The acute toxicity of 2,6 -dimethylheptan-4 -one (diisobutyl ketone or DIBK) to the rainbow trout was evaluated following OECD guidelines (OECD 203) over a 96 -hour flow-through exposure period. These data were used to calculate 24 -, 48 -, 72 -, and 96-hour LC50 values and a 96-hour NOEC. The study average recovery values ranged from 86.6 to 90.8% of target concentrations. The 24-, 48-, 72-, and 96-hour LC50 values were all 30.0 mg/L, with a 95% confidence interval of 23.1-38.9 mg/L. The 96-hour NOEC was 23.1 mg/l.

Description of key information

A 96-hour flow through acute test evaluated the toxicity of DIBK to the rainbow trout.  The test followed OECD 203 and meet GLP requirements.  The reported 96-hour LC50 value was 30 mg/L.

Key value for chemical safety assessment

LC50 for freshwater fish:
30 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 fish. A 2005 study evaluated the toxicity of DIBK to rainbow trout in a 96-hour flow through exposure. This GLP study followed OECD guidelines (OECD 203) and was rated a Klimisch score of 1, therefore it was selected as the Key study. The reported 96-hour LC50 value was 30 mg/L. A static 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 96 -hour LC50 value of >150 mg/L, the highest dose level tested.