Dichlobenil

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 July 1987 to 01 August 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

50 mL aliquots of test aquaria water were transferred to 70 mL culture tubes. 10 mL of toluene was added to each tube and shaken vigirously for three minutes. The phases were allowed to separate and the toluene phase was transferred to clean culture tubes. The samples were then diluted with toluene when necessary.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): acetone

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source: in-house culture
- Feeding during test
- Food type: algal suspension (Selenastrum capricornutum) with additional suspension of Tetramin, cereal leaves, vitamin and yeast
- Frequency: three times daily

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

238-278 mg/L as CaCO3 (well water)

Test temperature:

20 °C

pH:

8.0-8.2

Dissolved oxygen:

8.5-9.1 mg/L

Nominal and measured concentrations:

0, 0.3, 0.6, 1.2, 2.5 and 5.0 mg/L (nominal)

0, 0.32, 0.56, 1.0, 2.3 and 4.3 mg/L (measured)

Details on test conditions:

TEST SYSTEM
- Test vessel: 1 litre glass beakers
- Type (delete if not applicable): closed
- Type of flow-through: proportional diluter
- Renewal rate of test solution (frequency/flow rate): 5.7 times in a 24 hour period
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: ABC well water
- Total organic carbon: 0.6-3.8 mg/L
- Particulate matter: 0-1.3 mg/L
- Metals: <0.2 mg/L
- Chlorine: <0.05 mg/L
- Alkalinity: 300-320 mg/L (CaCO3)
- Conductivity: 480-540 µmhos/cm

OTHER TEST CONDITIONS
- Photoperiod: 16 hour light/8 hour dark

EFFECT PARAMETERS MEASURED: survival, abnormal effects and observance of first brood daily; length of surviving adults at study termination

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 0.3, 0.6, 1.2, 2.5 and 5.0 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

3.4 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

other: Maximum Acceptable Toxicant Concentration

Effect conc.:

1.5 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

other: survival, young/adult/reproduction day and adult mean length

Details on results:

An overview of the effects observed can be found in Table 1.

Daphnid survival was significantly different from the pooled controls at a mean measured concentration of 4.3 mg test material/L. The mean young/adult/reproduction day for 21 days were significantly affected in the mean measured exposure levels of 2.3 and 4.3 mg/L. No reproduction was observed in the 4.3 mg/L test concentration during this study. The average length in days to first brood for the controls was 8.5 days. The lengths to first brood were significantly affected in the mean measured exposure level of 1.0 and 4.3 mg/L. The effect identified for the 1.0 mg/L was considered aberrant since no effect was identified at the next higher test level. The adult daphnid lengths in the test material mean measured concentrations of 2.3 and 4.3 mg/L were significantly different from the pooled controls.

Table 1: Percent survival, young/adult reproduction day, length to first brood and adult length

Nominal conc. (mg/L)	Adult mean legth (mm)	Mean survival (%)	Mean young/adult reproduction day	Mean length to first brood (days)
0 (control)	3.8	95	5.4	8.5
0 (solvent control)	3.8	95	5.4	8.5
0.30	3.8	95	5.3	8.5
0.60	3.9	92	5.4	8.2
1.2	3.9	95	5.2	10^1
2.5	3.4*	95	3.6*	9
5.0	2.1*	18*	0*	21*

*significanly different from pooled controls

¹considered aberrant value

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the test, the 21 day EC50 based on immobility was 3.4 mg/L. Based on the statistical analysis of survival, young/adult/reproduction day, and adult mean length, the MATC (Maximum Acceptable Toxicant Concentration) limits were estimated to be the mean measured concentration of > 1.0 and < 2.3 mg/L. The estimated MATC value was calculated from these data to be 1.5 mg/L.

Executive summary:

In a GLP compliant chronic Daphnia toxicity study conducted in line with standardised guideline EPA OPP 72-4, the chronic toxicity to Daphnia of the test material over 21 days was determined. Daphnia were exposed to the test material at nominal test concentrations of 0, 0.30, 0.60, 1.2, 2.5 and 5 mg/L (equivalent to mean measured concentrations of 0.32, 0.56, 1.0, 2.3 and 4.3 mg/L). Under the conditions of the test, the 21 day EC₅₀ based on immobility was 3.4 mg/L. Based on the statistical analysis of survival, young/adult/reproduction day, and adult mean length, the MATC (Maximum Acceptable Toxicant Concentration) limits were estimated to be the mean measured concentration of > 1.0 and < 2.3 mg/L. The estimated MATC value was calculated from these data to be 1.5 mg/L.

Description of key information

The EC50 of the test material, based on immobility, was determined to be 3.4 mg/L according to a study performed in line with EPA Guideline 72-4 (equivalent to NOEC of 1.06 mg/L).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.06 mg/L

Additional information

In a GLP compliant chronic Daphnia toxicity study conducted in line with standardised guideline EPA OPP 72-4, the chronic toxicity to Daphnia of the test material over 21 days was determined.

Daphnia were exposed to the test material at nominal test concentrations of 0, 0.30, 0.60, 1.2, 2.5 and 5 mg/L (equivalent to mean measured concentrations of 0.32, 0.56, 1.0, 2.3 and 4.3 mg/L).

Under the conditions of the test, the 21 day EC₅₀ based on immobility was 3.4 mg/L. Based on the statistical analysis of survival, young/adult/reproduction day, and adult mean length, the MATC (Maximum Acceptable Toxicant Concentration) limits were estimated to be the mean measured concentration of > 1.0 and < 2.3 mg/L. The estimated MATC value was calculated from these data to be 1.5 mg/L (equivalent to a NOEC of 1.06 mg/L in line with Table R.10-1 of 'Guidance on information requirements and chemical safety assessment Chapter R.10').