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Administrative data

Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28 February 1992 to 3 March 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Documentation and inclusion of all necessary parameters per the method utilized and GLP standard. However, recoveries were poor for test solutions, indicating a potential inaccuracy in the actual exposure concentrations.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report date:
1992

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Deviations:
yes
Remarks:
(1) To control the test substance degradation, the stock solution was prepared daily. (2) The test organisms were fed at 21 h before test initiation.
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
Isooctyl acrylate
EC Number:
249-707-8
EC Name:
Isooctyl acrylate
Cas Number:
29590-42-9
Molecular formula:
C11H20O2
IUPAC Name:
6-methylheptyl acrylate
Details on test material:
- Name of test material (as cited in study report): Isooctyl acrylate (CAS No. 29590-42-9)
- Substance type: Pure substance
- Physical state: Liquid
- Analytical purity: 99.75%
- Lot/batch no.: Lot 3290
- Stability under test conditions: Stable in water
- Storage condition of test material: Stored at room temperature in an amber glass bottle and sealed in a metal container

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
Sampling of all test solutions occurred daily, including stock solutions, control solutions, and all exposure concentrations. Samples were collected each day 2 - 4 hours after the stock solution was renewed. Composite samples combining 200 mL of either control or test exposure solution from each replicate respectively were utilized, or individual samples were taken as appropriate. Samples were collected in 250 mL brown glass bottles and combined in 500 mL brown glass bottles. The report states that "the same bottles were used throughout the test.", but it is not clear if that is in reference to reusing bottles, or using new bottles of the same type for each sampling. A clean bottle was used to collect the blank control samples. Samples were combined except at the final time point or where mortality reached 100% in a replicate, whichever came first. It is indicated that analysis occurred daily.

Test solutions

Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

Test substance stock solution was prepared daily by adding 260 uL (229 mg) of test substance to 4 L of dilution water. Stock solution was mechanically stirred at ambient temperature for 15 minutes and then sonicated for 15 minutes. This solution was then mixed with 14 L of dilution water in a 19 L glass stock bottle that was preconditioned with a 12 mg/L test substance solution in deionized water. Final volume of stock solution was 18 L. Final concentration was ~12.7 mg/L (nominal). The 19L stock bottle was connected by a glass tube near the bottom of the stock bottle to a pre-calibrated metering pump to deliver the test substance stock solution to the test system.

Volume throughout the test was maintained at 1.5 L. Exposure vessels were kept covered except when sampling or removing organisms.

No evidence of undissolved test substance was noted.

Test organisms

Test organisms (species):
Pimephales promelas
Details on test organisms:
TEST ORGANISM
- Common name: Fathead minnow
- Source: Aquatic Biosystems Inc., Fort Collins, Colorado
- Age at study initiation (mean and range, SD): Juvenile

- Length at study termination (length definition, mean, range and SD): 1.6 +/- 0.57 cm *
- Weight at study termination (mean and range, SD): 0.025 +/- 0.012 g *

* NOTE: Length and weight of control fish were recorded at study termination.

- Feeding during test: None

ACCLIMATION
- Acclimation period: Fish were held and acclimated for 14 days prior to the test, during which they were exposed to dilution water for the last 9 days.
- Health during acclimation (any mortality observed): Test organisms appeared healthy. 0.6% mortality occurred during holding and acclimation period.

Study design

Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h

Test conditions

Hardness:
186-187 mg/L (as CaCO3)
Test temperature:
20.4-21.2 C
pH:
8.12-8.25
Dissolved oxygen:
8.4 - 8.7 mg/L
Nominal and measured concentrations:
All nominal test concentrations were calculated based on the measured test substance stock solutions, calibration of the metering system, and a dilution factor of 1.8. The mean test substance nominal concentrations were 0.35, 0.62, 1.12, 2.01, and 3.45 mg/L. Mean measured concentrations were 0.09, 0.15, 0.34, 0.82, and 1.75 mg/L respectively.

It was noted that the reported measured concentrations were corrected for daily well water spike recovery (81 +/- 15.4%), and that measured concentrations in exposure samples ranged from 24% to 51% of nominal. It was hypothesized that this discrepancy may be due to an abiotic process such as sorption to glass or volatility. The report states that daily analyses of the samples did not show the presence of test substance degradation products at any noticeable level. No definitive conclusion was offered.
Details on test conditions:
TEST SYSTEM
- Test vessel: Exposure vessels were 3 Liter rectangular glass tanks measuring 19.5 cm X 9.5 cm x 15.5 cm
- Type: Covered system
- Material, size, headspace, fill volume: 3 L glass tanks containing 1.5 L test solution
- Aeration: Test water was aerated for at least 24 hours prior to use in the test
- Type of flow-through: Proportional diluter
- Renewal rate of test solution (frequency/flow rate): Flow rate was calibrated and adjusted to provide 500 mL of exposure water per hour
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- Biomass loading rate: 0.02 g fish/L-day

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Shallow well water collected from the Two Harbors, MN area.
- Total organic carbon: Not given. COD = 9 mg/L
- Particulate matter: TSS < 4 mg/L
- Metals: Zinc 30 ug/L
Sodium 6.5 mg/L
Magnesium 16.3 mg/L
Iron 3 ug/L
Copper 13 ug/L
Calcium 46.5 mg/L

- Pesticides: None detected
- Ca/Mg ratio: 2.85
- Conductivity: 351 to 375 umhos/cm
- Intervals of water quality measurement: Total hardness and alkalinity were measured at test initiation. pH, dissolved oxygen (DO) concentrations, and temperature were monitored daily. Specific conductivity was measured at test initiation and termination.

OTHER TEST CONDITIONS
- Adjustment of pH: None
- Photoperiod: 16 hours light / 8 hours dark using cool white fluorescent lamps
- Light intensity: Not given


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

Test organisms were observed for signs of stress and mortality at 3 hours and 6 hours after test initiation, and then observed daily, at which point any dead test organisms were removed from the exposure vessels.
Reference substance (positive control):
no

Results and discussion

Effect concentrations
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
0.67 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Remarks on result:
other: 95% C.I.:  0.56 to 0.82 mg/L
Details on results:
- Mortality of control: None
- Other adverse effects control: None
- Abnormal responses: None
Reported statistics and error estimates:
For LC50 calculations, the test organism mortality data and the test substance mean measured concentrations were analyzed using the trimmed Spearman-Karber method. For the NOEC calculation, the data were analyzed using TOXSTAT statistical software. Each measured test substance concentration was corrected for the well water spike recovery before calculating the mean measured concentration.

Any other information on results incl. tables

Sublethal observations / clinical signs:

Table 1, Matrix spike recoveries for the test substance
Matrix Time of analysis (h) Test substance conc'n (mg/L) Percent recovery
nominal measured
Matrix ─ Deionized water  
Method blank  
  0 0.0 <0.04
  24 0.0 <0.04
  48 0.0 <0.04
  72 0.0 <0.04
  96 0.0 <0.04
Spike solution  
  0 0.22 0.24 109
  24 0.22 0.15 71
  48 0.22 0.16 75
  72 0.22 0.21 94
  96 0.22 0.19 89
Mean spike recovery 88 ± 15.3%    
Matrix ─ Well water  
Method blank  
  0 0.0 <0.04
  24 0.0 <0.04
  48 0.0 <0.04
  72 0.0 <0.04
  96 0.0 <0.04
Spike solution  
  0 0.22 0.23 104
  24 0.22 0.14 63
  48 0.22 0.16 74
  72 0.22 0.19 86
  96 0.22 0.17 77  
Mean spike recovery 81 ± 15.4%  

TEST SOLUTION ANALYSES

Table 2, Nominal and mean measured concentrations of substance during test
Test substance nominal conc'n (mg/L) Replicate Test substance measured conc'n (mg/L)  
0 hrs 24 hrs 48 hrs Reported Percent of nominal
72 hrs 96 hrs mean ± SD
0.0 (control) A <0.04  
  B <0.04    
  Composite <0.04 <0.04 <0.04 <0.04    
0.35 A 0.09  
  B 0.09    
  Composite 0.09 0.09 0.10 0.07   0.09±0.008 26
0.62 A 0.14  
  B 0.14    
  Composite 0.15 0.17 0.17 0.11   0.15 ± 0.024 24
1.12 A 0.35  
  B 0.34    
  Composite 0.34 0.37 0.39 0.23   0.34 ± 0.056 30
2.01 A 0.85  
  B 0.76    
  Composite 0.99 0.92 0.89 0.50   0.82 ± 0.174 41
3.45 A 7.64 1.81  
  B 7.12 1.76    
  Composite 1.71 1.71 1.75 ± 0.047 51
 

FISH DOSE RESPONSE

Table 3, Summary of Acute Toxicity of Isooctyl Acrylate to the Fathead Minnow (Pimephales promelas) Under Flow-Through Conditions
Mean Measured Conc., mg/L
Percent Mortality
24-hrs 48-hrs 72-hrs 96-hrs
Blank Control 0 0 0 0
0.09 0 0 0 0
0.15 0 0 0 0
0.34 0 5 5 5
0.82 0 35 65 65
1.75 5 100 100 100
LC50 Not calculable 0.86 0.67 0.67
95% C.I. Not calculable 0.71 - 1.05 0.56 - 0.82 0.56 - 0.82

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The 96-hour LC50 of the test substance to fathead minnow (Pimephales promelas) is 0.67 mg/L. The NOEC, mased on mortality, is 0.34 mg/L.
Executive summary:

In a 96-h acute toxicity study, fathead minnow (Pimephales promelas) were exposed to isooctyl acrylate (CAS No. 29590-42-9) at nominal concentrations of 0 (control), 0.35, 0.62, 1.12, 2.01, and 3.45 mg/L and mean measured concentrations of 0 (control), 0.09, 0.15, 0.34, 0.82, and 1.75 mg/L under flow-through conditions.  The 96-h LC50 was 0.67 mg/L.  The NOEC value based on mortality was 0.34 mg/L.  Sublethal effects were not observed. 

This toxicity study is classified as acceptable and satisfies the guideline requirement for acute fathead minnow toxicity study. The reliability rating is 2 (reliable with restrictions). The study was conducted under GLP with measured concentrations. However, recoveries were poor for test solutions, indicating a potential inaccuracy in the actual exposure concentrations.  

Results Synopsis  

Test organism size/age: 1.6 cm (+/-0.57) / Juvenile

Test Type: flow-through

LC50:  0.67 mg/L                         95% C.I.:  0.56 to 0.82 mg/L

NOEC:  0.34 mg/L                         

Endpoint(s) Effected: Mortality