Dichloromethylbenzene

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Method comparable to guideline, analytical monitoring was performed, all validity criteria fulfilled

Justification for type of information:

The substance described in this dossier is an isomeric mixture of five position isomers of dichlorotoluene. The similarities concerning chemical structure and key intrinsic properties such as log Kow and water solubility lead to the assumption that the values for ecotoxicological endpoints will also be very similar for the individual isomers and the mixture of isomers and that therefore results obtained with isomers can be useful for the assessment of the mixture. This assumption is supported by the results obtained in acute fish toxicity studies performed with the isomers: 2,4 -, 3,4 -, 2,3 - and 2,6 - DCT as well as with two different mixtures including the one which is to be assessed in this dossier (see following table). The results are nearly identical for all tested isomers with the exception of the result obtained for 2,3-DCT, which is considerable higher. However, this study is attributed a reliability of only 4.

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Qualifier:

no guideline followed

Principles of method if other than guideline:

A static acute toxicity test was performed with 2,4-dichloromethylbenzene to Daphnia magna over a period of 48 hours. Analytical monitoring was performed.

GLP compliance:

not specified

Specific details on test material used for the study:

Not indicated

Analytical monitoring:

yes

Details on sampling:

- Sampling method: samples were extracted into hexane or iso-octane at time = 0 and after 48 h exposure

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test solutions were obtained from saturated stock solutions prepared by adding excess chemical to dilution water and stirring for a minimum of 20 hours. Liquids (such as 2,4-dichlorotoluene) were slowly stirred to avoid dispersion of droplets in water.

- Evidence of undissolved material (e.g. precipitate, surface film, etc):

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Age at study initiation (mean and range, SD): less than 24 h

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

Not indicated

Hardness:

160 +/- 20 mg/L as CaCO3 (dilution water)

Test temperature:

21.5 +/- 1 °C

pH:

8.3 +/-1 (dilution water)

Dissolved oxygen:

oxygen saturation

Salinity:

not applicable

Nominal and measured concentrations:

a minimum of 5 concentrations were tested

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 50-ml glass flasks, completely filled
- closed with glass stoppers
- 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: bottled natural mineral water diluted with distilled water and aerated to reach oxygen saturation
- Conductivity: 311 +/- 33 µS/cm
- Intervals of water quality measurement: at the ebeginning and at the end of the test temperature, pH dissolved oxygen and conductivity were measured in the control and in a minimum of two concentrations; hardness was measured in the control and the highest concentration


OTHER TEST CONDITIONS
- Photoperiod: 16 h light, 8 h dark



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : immobilisation


TEST CONCENTRATIONS
- Spacing factor for test concentrations: geometric factor of 1.2 to 1.8
- Range finding study: yes, details are not provided

Reference substance (positive control):

not specified

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.26 mg/L

Nominal / measured:

nominal

Basis for effect:

other: immobility

Remarks on result:

other: 95% C. I.: 1.09 - 1.49

Details on results:

- Mortality of control: at the end of the test <= 10 % (immobility)
- low variability between preliminary and full tests (SD < 0.1 log units)
- dissolved oxygen concentration >= 75 % (i.e. >= 6.7 mg/L ; the guidline requires >=3 mg/L)
- the chemical concentrations were stable (< 20% loss)

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Probit analysis was used for the EC50-calculation.

No remarks

Validity criteria fulfilled:

yes

Remarks:

immobility in the control not ore than 10 %, oxygen saturation; dissolved oxygen concentration >= 3 mg/L, the chemical concentrations were stable (< 20% loss)

Conclusions:

The 48-hour EC50 of 2,4 - dichloromethylbenzene to Daphnia was 1.26 mg/L.

Executive summary:

The 48-hr-acute toxicity of 2,4 - dichloromethylbenzene to Daphnia magna was studied under static conditions. Daphnids were exposed to a minimum of 5 concentrations with a spacing factor of 1.2 to 1.8. Immobilization was observed at 48h. All validity criteria are fulfilled. The 48-hour EC50 was 1.26 mg/L.

Reference: Marchini, 1999

Description of key information

The 48-hr EC50  toxicity of 2,4-dichloromethylbenzene to Daphnia magna was 1.26 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.26 mg/L

Additional information

Key study:

The 48-hr-acute toxicity of 2,4 -dichlorotoluene to Daphnia magna was studied under static conditions. Daphnids were exposed to a minimum of 5 concentrations with a spacing factor of 1.2 to 1.8. Immobilization was observed at 48h. All validity criteria are fulfilled. The 48-hour EC50 was 1.26 mg/L.

Reference: Marchini, 1999

The similarities between the isomers concerning chemical structure and key intrinsic properties such as log kow and water solubility as well as nearly identical results for acute fish toxicity obtained for the mixture and individual isomers justify read across from tests results obtained with the individual isomers 2,4-DCT and 3,4-DCT to the mixture. A more detailed argumentation for read-across is given in the Summary "Aquatic toxicity".

Supporting studies:

The 48-hr-acute toxicity of 2,4-dichlorotoluene to Ceriodaphnia cf. dubia was studied under static conditions with analytical monitoring. The 48-hour EC50 was 1.0 mg/L (based on initial measured concentrations). Although this study and the key study have the same reliability index according to Klimisch, it is considered not to be as reliable as the key study because based on the information provided in the report only compliance with one of three validity criteria can be proven. Therefore, uncertainty remains as to whether the other two validity criteria have been fulfilled. The study is therefore not chosen as key study, but nevertheless confirms the result of the key study. The slightly lower EC50 may be explained by the closed sytem and the use of a vehicle.

Reference: Rose, 1998

The 48-hr-acute toxicity of 2,4 -dichlorotoluene to Daphnia magna was determined under semi-static conditions in a 21 -d study. The 48-hour EC50 was 6.5 mg/L. Reliability not assignable.

Reference: EA Japan, 1992 (21 h)

Disregarded study

The 48-hr-acute toxicity of 2,4 -dichlorotoluene to < 2 days old Daphnia magna was studied under static conditions. The 48-hour EC50 was 0.6 mg/L. The 48-hr-acute toxicity of 2,4 -and 3,4 -dichlorotoluene was further calculated from the log Kow by using a QSAR. The value obtained was 2 mg/L for both isomers. The experimental part of the study is considered not to be reliable (The age of the used daphnia was too high and the initial measured concentrations did not achieve 80% of the nominal concentrations) and the reliability of the QSAR may not be assessed due to reporting gaps. The study is therefore disregarded.

Reference: Hermens, 1984

Further study:

The 24-hr-acute toxicity of 2,4 -dichlorotoluene to Daphnia magna was studied under semi-static conditions. The 24-hour EC50 was 19 mg/L. The study is considered not to be reliable.

Reference: EA Japan, 1992 (24 h)