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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
Study period:
15-17 February 1994
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
This study was performed according with the guideline EPA-600/4-90/013, as well as in accordance with GLP principles. However, nominal concentrations are not confirmed by analytical measurements. Therefore, a Klimisch code 2 was assigned. Since test solutions were renewed after 24h and the read-across substance TMAH was stable in an algae study, it can be assumed that the exposure was constant.
Qualifier:
according to
Guideline:
other: EPA-600/4-90/013
Deviations:
not specified
Qualifier:
according to
Guideline:
other: ASTM, 1993. Standard E 729-88a, Book of Standards Volume 11.04.
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
A working stock solution of methyltributylammonium chloride was prepared on the day the test was initiated. The stock solution was prepared on a weight-to-volume basis in a class A volumetric flask. The concentration was 10mg/mL. From this stock solution, five exposure concentrations were prepared for each test.

For test 1 (reconstituted fresh water), the exposure solution was prepared with moderately hard reconstituted fresh water, which was prepared with glass-distilled deionized water and reagent grade salts following the procedures outlined in US EPA-600/4-90/013.
For test 2 (effluent and river water), an effluent solution was prepared with 6.8% effluent (collected from outfall 002, GE-Plastics, Mt. Vernon, Indiana, USA) in Ohio River water on a volume-to-volume basis.

Test solution renewals were accomplished following 24 h of exposure by transferring test organisms into freshly prepared test solutions.
Test organisms (species):
Ceriodaphnia dubia
Details on test organisms:
TEST ORGANISM
- Common name: Water flea
- Source: Woodward-Clyde Consultants (WCC) in-house laboratory cultures
- Age at study initiation (mean and range, SD): Less or equal to 24 h
- Feeding during test: None
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
Test 1 (reconstituted fresh water): 100 (control group only)
Test 2 (effluent and river water): 150 (control group only)
Test temperature:
Test 1 (reconstituted fresh water) and test 2 (effluent and river water): 25±1°C
pH:
Test 1 (reconstituted fresh water): 7.66 -8.37
Test 2 (effluent and river water): 7.85 - 8.66
Dissolved oxygen:
Test 1 (reconstituted fresh water): 8.2 -8.8
Test 2 (effluent and river water): 8.5 - 9.0
Nominal and measured concentrations:
Nominal test material concentrations (mg/L):
Test 1 (reconstituted fresh water): Control (reconstituted fresh water), 8.1, 27, 90, 300 and 1000
Test 2 (effluent and river water): Control (effluent and river water), 8.1, 27, 90, 300 and 1000
Details on test conditions:
TEST SYSTEM
- Test vessel: 30mL Styrine
- Material, size, headspace, fill volume: Styrine, with a capacity of 30mL and filled with 15mL
- Aeration: None
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
Test 1 (reconstituted fresh water) - in moderately hard reconstituted fresh water prepared from glass-distilled deionized water and reagent grade salts following the procedures outlined in EPA-600/4-90/013. Test 2 (effluent and river water) - in 6.9% effluent solution prepared with Ohio River (USA) water on a volume-to-volume basis.
- Alkalinity:
Test 1 (reconstituted fresh water): 70 (control group only)
Test 2 (effluent and river water): 80 (control group only)

OTHER TEST CONDITIONS
- Photoperiod: 16 h light / 8 h dark
- Light intensity: 50-100 Ft. candles

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Mortality and behavioral characteristics

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
Test 1 (reconstituted fresh water) and test 2 (effluent and river water): Approximately 3.
Reference substance (positive control):
no
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
12.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 95% CL: 8.7-16.6 mg/L (Test 1 - reconstituted fresh water).
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
9.2 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks on result:
other: 95% CL: 6.5-12.4 mg/L (Test 1 - reconstituted fresh water). These results are recalculated by the reviewer based on a MTBAC content of 75% in the test material.
Details on results:
- The effect levels for test 2 (effluent and river water) were the following (mg test material/L):
EC50: 52.4 (95% CL: 46.6 - 58.9 mg/L)
Validity criteria fulfilled:
not specified
Conclusions:
Water fleas (Ceriodaphnia dubia) were more sensitive to methyltributylammonium chloride when exposure was performed using reconstituted fresh water to prepare exposure solutions compared to industrial effluent solutions prepared in Ohio River water. Based on nominal test material concentrations the resulting 48h-EC50 was equal to 12.3 mg/L and the NOEC was 8.1 mg/L. This corresponds with a nominal 48h-LC50 of 9.2 mg MTBAC/L and a NOEC of 6.1 mg MTBAC/L
Executive summary:

In two 48-h acute toxicity study, water fleas (Ceriodaphnia dubia) were exposed to methyltributylammonium chloride at nominal test material concentrations of 0 (control), 8.1, 27, 90, 300 and 1000 mg/L.

In the test conducted with reconstituted fresh water the 48h-EC50 was 12.3 mg test material/L.This corresponds with a nominal 48h-EC50 of 9.2 mg MTBAC/L. Test 2, conducted with 6.8% industrial effluent solution in Ohio River water, showed that water fleas (Ceriodaphnia dubia) were less sensitive to methyltributylammonium chloride toxicity compared to the test conducted with reconstituded fresh water. The resulting 48h-EC50 was 52.4 mg test material/L. This corresponds with a nominal 48h-EC50 of 39 mg MTBAC/L.

Analytical confirmation of test concentrations were not performed and the water quality of Ohio river water was not properly determined (e.g.dissolved organic carbon). Nevertheless, since test solutions were renewed after 24h and the read-across substance TMAH was stable in an algae study (Scheerbaum, 2011), it can be assumed that the actual exposure to MTBAC was in agreement with the nominal MTBAC concentration.

For the evaluation of the intrinsic toxicity of the substance, only the test results with reconstituted water should be used, because in the other tests (applying 6.8% industrial effluent solution in Ohio River water), the test medium was not well defined.

Description of key information

In test 1 conducted with reconstituted fresh water the 48h-EC50 was 12.3 mg test material/L. This corresponds with a nominal 48h-EC50 of 9.2 mg MTBAC/L.
In test 2 conducted with 6.8% industrial effluent solution in Ohio River water, the resulting 48h-EC50 was 52.4 mg/L. This corresponds with a nominal 48h-EC50 of 39 mg MTBAC/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
9.2 mg/L

Additional information

In two 48-h acute toxicity study, water fleas(Ceriodaphnia dubia) were exposed to 75% methyltributylammonium chloride at nominal test material concentrations of 0 (control), 8.1, 27, 90, 300 and 1000 mg/L.

In the test conducted with reconstituted fresh water the nominal 48h-EC50 was 12.3 mg test material/L. This corresponds with a nominal 48h-EC50 of 9.2 mg MTBAC/L. Test 2, conducted with 6.8% industrial effluent solution in Ohio River water, showed that water fleas (Ceriodaphnia dubia) were less sensitive to methyltributylammonium chloride toxicity when compared to the test conducted with reconstituded fresh water. The resulting 48h-EC50 was 52.4 mg test material/L. This corresponds with a nominal 48h-EC50 of 39 mg MTBAC/L.

Analytical confirmation of test concentrations were not performed and the water quality of Ohio river water was not properly determined (e.g.dissolved organic carbon). Nevertheless, since test solutions were renewed after 24h and the read-across substance TMAH was stable in an algae study (TMAH Consortium 2005 and Scheerbaum 2011), it can be assumed that the actual exposure to MTBAC was in agreement with the nominal MTBAC concentration.

For the evaluation of the intrinsic toxicity of the substance, only the test results with reconstituted water should be used, because in the other tests (applying 6.8% industrial effluent solution in Ohio River water), the test medium was not well defined.