Chlorobenzene

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Non-GLP study similar to current guideline, basic data given, validity criteria not confirmed

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Deviations:

no

GLP compliance:

no

Analytical monitoring:

yes

Details on sampling:

Verification before and after renewal

Vehicle:

yes

Details on test solutions:

DMSO was used if neccesary

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Hardness:

Reconstituted water: 210 mg CaCO3/L

Test temperature:

Approx. 24°C

pH:

Reconstituted water: 8.0-8.2

Dissolved oxygen:

Reconstituted water: 7.7 mg/L

Nominal and measured concentrations:

The mean concentrations of chlorobenzene in the semistatic test was below the nominal concentrations. The mean measured concentrations during the tests with chlorobenzene were 85, 60, 65, 45, 55 and 60 % ofthe nominal concentrations, respectively.

Details on test conditions:

Fertilized eggs of zebra fish (Brachydanio rerio) in the blastula stage were obtained from a stock culture at the TNO Iabaratory of 50-100 eggs ( < 6 h
after spawning) into 1-liter glass test vessels filled with 1-liter test solution. After l day all non-viable eggs were removed and the number of viable eggs was reduced to a maximum of 40 per concentration. In case the number of viable eggs in the controls fell below 25 after 48 h, the test was discarded. The embryolarval stages were exposed in a semistatic manner to 7-8 toxicant concentrations and a control for a period of 28 days. Upon completion of hatching (4-5 days), the fry were transferred into two vessels per concentration. The fry were fed equal amounts of the rotifer Brachionus rubens, obtained from a Iabaratory culture. After 7 days this food was supplemented by 48-h old nauplii of the brine shrimp Artemia salina. The nauplii were enriched with Selco, a commercial concentrate for nutritional enrichment of live food for fish.
The toxicity tests were carried out in a constant-temperature room at 24 ± 2 °C and a photoperiod of 12 h. Dead eggs and larvae were counted and removed daily. At the end of the test period the surviving fish were anesthetized in buffered tricaine methaue sulphonate (MS 222, Sandoz, Basel) for final length measurements. The number of microscopically malformed fish was determined under a microscope (magnification 30 x ).
The ratio between the concentrations was 1.8. The test solutions were renewed 3 times a week. In the tests with the aniline derivatives, the test solutions were gently aerated, in the chlorobenzene tests they were not. In several instances dimethyl sulphoxide (DMSO) was used as solvent for the test compounds. DMSO concentrations were kept below 100 µL/L. The effects of DMSO were verified in solvent control experiments. pH and 02 concentrations were measured at regular intervals.

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

10.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

larval development

Remarks on result:

other: 95% CL: 9.1-11.9

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

4.8 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

larval development

Temporal changes of the NOEC (effects on survival and embryo-hatchability) for chlorobenzene

Compound	Concentration (mg/L)
	7 days	14 days	21 days	28 days
chlorobenzene	8.5	8.5	8.5	8.5

Validity criteria fulfilled:

not specified

Conclusions:

In the early life stage fish toxicity test, the larvae of Danio rerio were exposed to chlorbenzene in a semi-static test system. After 28 days a LC50 of 10.3 mg/L was determined and a NOEC of 4.8 mg/L was calculated; based on measured concentrations.

Executive summary:

In the early life stage fish toxicity test, the larvae of Danio rerio were exposed to chlorbenzene in a semi-static test system. After 28 days a LC50 of 10.3 mg/L was determined and a NOEC of 4.8 mg/L was calculated; based on measured concentrations.

Reference 2

Endpoint:

long-term toxicity to fish, other

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

09 May 2022 to 14 June 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Remarks:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its CHRONIC TOXICITY TO FISH (32-DAY EC10). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

Justification for type of information:

1. SOFTWARE
iSafeRat® – in Silico Algorithms For Environmental Risk And Toxicity

2. MODEL (incl. version number)
iSafeRat® fishEC10 v1.5

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
Clc1ccccc1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached QMRF

5. APPLICABILITY DOMAIN
See attached Study Report with QPRF in Annex

6. ADEQUACY OF THE RESULT
See attached Study Report with QPRF in Annex

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Deviations:

not applicable

Remarks:

QSAR model

Principles of method if other than guideline:

The CHRONIC TOXICITY TO FISH (32-DAY EC10) was determined using iSafeRat® fishEC10, a validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis) (Bauer et al., 2018). The QSAR is based on validated data for a training set of 27 chemicals derived from 32-day test on fish, for which the concentrations of the test item has been determined by chemical analyses over the test period.

GLP compliance:

no

Remarks:

QSAR model

Specific details on test material used for the study:

Water Solubility 5.38E+02 mg/L (Yalkowsky et al., 1979)
Mechanism of action MechoA 1.1: non-polar narcosis (Bauer et al., 2018)

Analytical monitoring:

no

Remarks:

QSAR model

Details on sampling:

not applicable

Vehicle:

no

Details on test solutions:

not applicable

Test organisms (species):

other: Danio rerio, Pimephales promelas, Cyprinus carpio, Oncorhynchus mykiss

Details on test organisms:

none

Test type:

other: QSAR model

Water media type:

freshwater

Limit test:

no

Total exposure duration:

32 d

Remarks on exposure duration:

Results from a test duration of 32 to 102 days were included. Equilibrium between organisms and external medium was expected to be equivalent from 32 days.

Post exposure observation period:

not applicable

Hardness:

The QSAR is based on data from studies performed at acceptable hardness to ensure control survival.

Test temperature:

The temperatures varied from approximately from 10 to 25 °C depending on the fish species used to construct the algorithm.

pH:

Test results were taken from studies with measured pHs between 6.0 - 8.5.

Dissolved oxygen:

The model is based on data from studies performed at acceptable oxygen concentrations (generally >60%).

Salinity:

not applicable

Conductivity:

not applicable

Nominal and measured concentrations:

Studies were used only where sufficient evidence was presented to determine that the stubstance was stable under test conditions (i.e. maintened within ± 20 % of the nominal) or, if not, the result was based on measured concentrations as geometric mean.

Details on test conditions:

Preferentially results from a flow-through test were used. However semi-static with daily renewal of test solutions and the control was accepted (preferably accompanied by analytical measurements over the study period). For suspected volatile substances only tests performed in closed vessels were accepted unless accompanying analytical monitoring proved such a design was not necessary.

Reference substance (positive control):

not required

Key result

Duration:

32 d

Dose descriptor:

EC10

Remarks:

equivalent to MATC

Effect conc.:

3.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

other: based on the lowest value measured for the following effects: juvenile growth, juvenile survival or the hatchability

Details on results:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its CHRONIC TOXICITY TO FISH (32-DAY EC10). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

95% confidence interval (α = 0.05): 2.5E+00 - 4.1E+00 mg/L

Applicability Domain

 

Descriptor domain

The Subcooled Liquid Water Solubility value (5.38E+02 mg/L or -2.321 in log10 (mol/L)) given as the input to the iSafeRat® fishEC10 model falls within the descriptor domain of the model between a Subcooled Liquid Water Solubility of -5.140 to 0.702 in log10 (mol/L).

 

Structural fragment domain

The variability of structure in the training set is not considered as a relevant domain since the model is based on a mechanistic approach (mechanism of action). Since the MechoA is related to the molecular structure, the following list of chemical moieties can give an overview of the structural domain:

• Alcohol


• Alkane


• Alkene


• Anthraquinones


• Aromatic hydrocarbons and polycyclic aromatic hydrocarbon


• Ester


• Ether


• Halogenated hydrocarbons


• Ketone

The test item as a halogenated aromatic hydrocarbon can be taken into account by the model.

 

Mechanistic domain:

The iSafeRat® fishEC10 model can reliably predict the aquatic toxicity for chemicals with the following mechanisms of action of toxicity (MechoA):

• non-polar narcosis (MechoA 1.1)


• mono-/poly-esters whose hydrolysis products are narcotics (MechoA 2.1)

The MechoA of molecules is predicted directly from the structure. The test item as a halogenated aromatic hydrocarbon is expected to exert a MechoA 1.1 and can be taken into account by the model (Bauer et al., 2018).

Validity criteria fulfilled:

yes

Conclusions:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its CHRONIC TOXICITY TO FISH (32-DAY EC10). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.
The CHRONIC TOXICITY TO FISH (32-DAY EC10) of the test item was predicted as 3.2E+00 mg/L.
95% confidence interval (α = 0.05): 2.5E+00 – 4.1E+00 mg/L.

Executive summary:

A Quantitative Structure Activity Relationship (QSAR) model was used to calculate the CHRONIC TOXICITY TO FISH (32-DAY EC10) for the test item. This QSAR model has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following Guideline for Testing of Chemicals No. 210, "Fish, Early-life Stage Toxicity Test" (OECD, 2013). The criterion predicted was the EC10 (10% Effective Concentration), a concentration which is expected to cause an effect of 10% on growth or reproducibility within a period of 32 days.

 

The CHRONIC TOXICITY TO FISH (32-DAY EC10) was determined using iSafeRat® fishEC10, a validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis) (Bauer et al., 2018). The QSAR is based on validated data for a training set of 27 chemicals derived from 32-day test on fish, for which the concentrations of the test item had been determined by chemical analyses over the test period.

 

The test item falls within the applicability domain of the model and can therefore be considered a reliably prediction for CHRONIC TOXICITY TO FISH (32-DAY EC10). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

The CHRONIC TOXICITY TO FISH (32-DAY EC10) of the test item was predicted as 3.2E+00 mg/L.
95% confidence interval (α = 0.05): 2.5E+00 – 4.1E+00 mg/L

Description of key information

32d-EC10 (fish) = 3.2 mg/L (95% CI: 2.5 - 4.1 mg/L); iSafeRat® High-Accuracy-Quantitative Structure-Activity Relationship; KREATiS (2022).

28d-NOEC (Danio rerio) = 4.8 mg/L; OECD 210-non GLP; Van Leeuwen (1990).

Based on weight of evidence approach, worst-case value is used as a key value for chemical safety assessment: 32d-EC10 (fish) = 3.2 mg/L 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

EC10

Remarks:

32d

Effect concentration:

3.2 mg/L

Additional information

One High-Accuracy QSAR and one experimental results are available and used in a weight of evidence approach to determine the long-term toxicity to fish.

Chlorobenzen falls within the applicability domain of the model (iSafeRat®) and was therefore reliably predicted for its chronic toxicity to fish with a 32-day EC10 of 3.2 mg/L. The experimental study was performed according to OECD 210 guideline (not GLP) on Danio rerio with a NOEC(28d) of 4.8 mg/L. Both results are in the same order of toxicity (>1 mg/L) and confirm the low chronic toxicity of the substance to fish. The lowest value has been used as worst case value for key value of chemical safety assessment.