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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11 Jan 1993 - 13 Jan 1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The solvent used for the dilution of CMK was not indicated.
Qualifier:
according to
Guideline:
EPA OPP 72-2 (Aquatic Invertebrate Acute Toxicity Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: control, solvent control, 1, 2, 3, 4, 5 mg a.i./L
- Sampling method: Duplicate samples were taken after 0 and 48 h. The final analytical samples after 48 h were combined into one vessel. Samples were shipped to ABC Laboratories Inc., Columbia, Missouri, USA on wet ice for analysis.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Controls: yes, water and solvent control
- Chemical name of vehicle: not specified
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Source: The strain was obtained from Aquatic BioSystems, Fort Collins, Colorado.
- Age: ≤ 24 hours old neonates
- Feeding during test: none

ACCLIMATION
- Type and amount of food: algae (Scenedesmus subspicatus and Ankistrodemus falcatus) and /or a yeast/troutchow/cerophyll mixture
- Feeding frequency: daily
- Method of breeding: The stock culture was maintained in hard blended water and fed daily with algae (Selenastrum capricornutum and Ankistrodesmus falcatus) and/or a yeast/troutchow/cerophyll mixture. Daphnia culture techniques were based on those described by USEPA (1985). The holding area was maintained on a 16-hour daylight photoperiod and a 20 °C temperature range.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
164 mg/L
Test temperature:
19.8 - 19.9 °C
pH:
8.0 - 8.2
Dissolved oxygen:
8.6 - 9.1 mg/L
Conductivity:
344 µmhos
Nominal and measured concentrations:
nominal: control, solvent control, 1.0, 2.0, 3.0, 4.0 and 5.0 mg a.i./L
measured: < 0.1, < 0.1, 0.88, 1.73, 2.67, 3.90 and 5.52 mg a.i./L
Details on test conditions:
TEST SYSTEM
- Test vessel: 2 L glass beakers
- Material, size, headspace, fill volume: glass, 2 L, headspace: 1 L, fill volume: 1 L
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Process water (spring water blended with treated city water)
- Hardness: 164 mg/L
- Alkalinity: 134 mg/L
- Conductivity: 344 µmhos

OTHER TEST CONDITIONS
- Photoperiod: 16:8 light-dark cycle with 30 min transition period.
- Light intensity: approx. 645 - 700 lux

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 1, 2.5 and 5 mg/L
- Results used to determine the conditions for the definitive study: At test termination there was 100 % mortality in the 5 mg/L level and 0 % mortality in the remaining test levels and controls.
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
2.29 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
mobility
Remarks:
sublethal effects
Remarks on result:
other: 95% CL: 1.73 - 2.67 mg/L
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
3.9 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks on result:
other: 95% CL = 2.67 - 5.52 mg/L
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
1.73 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks:
sublethal effects
Details on results:
- Mortality of control: 0%
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: The test solutions were clear and colorless
Reported statistics and error estimates:
Statistical analysis was obtained by employing a computerized program. The LC50 and EC50 values were calculated using one of the following statistical methods: binomial probability, moving average angel and probit, depending on the characteristics of the data. Based on the data the EC50 was calculated using binomial probability.

Table 1: Cumulative mortality and behavioural observations (after 24 and 48 h)

Mean measured Concentration

[mg a.i./L]

Effects on Daphnia magna

24 hours

48 hours

Dead

Obs.

Dead

Obs.

Control

0

20 N

0

20 N

Solvent control

0

20 N

0

20 N

0.88

0

20 N

0

20 N

1.73

0

20 N

0

20 N

2.67

0

16 N
4 OB

0

3 N
16 OB
1 OB, VLM

3.90

0

8 N
12 OB

10

10 OB, VLM

5.52

6

14 OB

20

0

Abbreviations of behavioural observations

N        Normal

OB      On bottom of vessel

VLM   Very little movement

Table 2: Validity criteria

Criterion from the guideline

Outcome

Validity criterion fulfilled

In the control, including the control containing the solubilising agent, not more than 10% of the daphnids should have been immobilized.

0 %

yes

The dissolved oxygen concentration at the end of the test should be ≥ 3 mg/L in control and test vessels.

8.6 mg/L

yes

Validity criteria fulfilled:
yes
Remarks:
For further details please refer to “Any other information on results incl. tables”.
Conclusions:
EC50 (48 h) = 2.29 mg/L
Executive summary:

Juvenile Daphnia magna were exposed in a static test system for 48 h to five concentrations of p-chloro-m-cresol according to U.S.-EPA FIFRA § 72-2: “Acute toxicity test for freshwater invertebrates”. Mortality of daphnids showed a clear dose-response relationship: no daphnids died in the lowest concentrations, while no Daphnia survived in the highest concentration. The EC50 value after 48 h was determined to be 2.29 mg a.i./L. Concentrations were measured at day 0 and at day 2 and range between 87 and 110 % of nominal, indicating that the test substance was stable for the duration of the study. All results were based on mean arithmetric measured concentrations. The test is considered valid and the result is used in the risk assessment.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Refer to analogue justification document provided in IUCLID section 13.
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
2.29 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks:
sublethal effects
Remarks on result:
other: 95% C.I.: 1.73 - 2.67 mg/L
Remarks:
source, CAS 59-50-7, key rel 2, Gagliano & Bowers 1993
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
3.9 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks on result:
other: 95% C.I.: 2.67 - 5.52 mg/L
Remarks:
source, CAS 59-50-7, key rel 2, Gagliano & Bowers 1993
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
1.73 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks:
sublethal effects
Remarks on result:
other:
Remarks:
source, CAS 59-50-7, key rel 2, Gagliano & Bowers 1993

Description of key information

EC50 (48 h): 2.29 mg/L (measured arithmetic mean, Daphnia magna), read-across

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
2.29 mg/L

Additional information

No study investigating the toxicity of sodium p-chloro-m-cresolate (CAS 15733-22-9)to acute daphnia is available. Therefore, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to the source substance(p-chloro-m-cresol, CAS 59-50-7) which isthe main transformation product of the target substancesodium p-chloro-m-cresolate (CAS 15733-22-9) is applied.

The source substance p-chloro-m-cresol is the common compound in this analogue approach and is solely responsible for the (absence of) effects.Thus, the source substance is considered a suitable representative for the evaluation of the toxicity of the target substance to aquatic organisms. The read-across approach is justified in detail within the analogue justification in IUCLID section 13.

One experimental study is available investigating the short-term effects of the source substance p-chloro-m-cresol (CAS 59-50-7) to aquatic invertebrates (Gagliano & Bowers 1993). The test was conducted according to according to U.S.-EPA FIFRA § 72-2: “Acute toxicity test for freshwater invertebrates”. Juvenile Daphnia magna were exposed in a static test system for 48 h to nominal concentrations of 1.0, 2.0, 3.0, 4.0 and 5.0 mg/L, resulting in measured concentrations of 0.88, 1.73, 2.67, 3.90 and 5.52 mg/L. Mortality of daphnids showed a clear dose-response relationship: no daphnids died in the lowest concentrations, while no Daphnia survived in the highest concentration. The EC50 value after 48 h was determined to be 2.29 mg/L. Concentrations were measured at day 0 and at day 2 and range between 87 and 110 % of nominal, indicating that the test substance was stable for the duration of the study. All results based on arithmetic mean measured concentrations.

Based on the available results from a structurally similar source substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is the main transformation product of the target substance and is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded thatsodium p-chloro-m-cresolatehas effects in the same range as the target substance.