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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-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:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied. Please refer to a full version of Read-across statement attached in the section 13 "Assessment reports".

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The underlying hypothesis for the read-across is that the target and the source substance have similar toxicological properties (including the same target organs) due to their structural similarity, resemblance to their chemical reactivity, and therefore a similar mode of action.
The source substance ‘Mixture of 1,3-diisopropylbenzene and 1,4-diisopropylbenzene' is a mixture of structural isomers, 1,3- diisopropylbenzene(target substance) and 1,4-diisopropylbenzene. The physico-chemical properties are highly equivalent based on the high structural similarity. As a conclusion, it is scientifically justified to address the endpoint Long-term toxicity to aquatic invertebrates with data on this mixture of isomers.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source substance: Mixture of 1,3-diisopropylbenzene and 1,4-diisopropylbenzene (Diisopropylbenzene), CAS no. 25321-09-9
structural formula: C12H18
Smiles: CC(C)C1=CC=CC=C1C(C)C
Molecular weight: 162 g/mol
CAS 25321-09-9
EC No 246-835-6
purity: not specified

target substance: 1.3-diisopropylbenzene (or m-DIPB)
structural formula: C12H18
Smiles: CC(C)c1cccc(c1)C(C)C
Molecular weight: 162 g/mol
CAS 99-62-7
EC No 202-773-1
purity: not specified

No additional information is available on purity of the source and the target substances. Both substances are normally of high purity, containing only minor amounts of impurities that do not influence the read-across validity.

3. ANALOGUE APPROACH JUSTIFICATION
Please refer to the full version of the read-across statement attached in the section 13 "Assessment reports".

4. DATA MATRIX
Please refer to the full version of the read-across statement attached in the section 13 "Assessment reports".
Reason / purpose for cross-reference:
read-across source
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.063 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
0.168 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LC50
Effect conc.:
0.22 mg/L
95% CI:
>= 0.156 - <= 0.346
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
0.154 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: (95 % confidence interval: not calculated)
Details on results:
- Mortality of control: The mortality rate of Daphnia magna in the control and the control with the aid was 0 % at the end of the exposure period, which met the criterion of less than 20 % for the test to be successful. The mortality rate in the highest concentration was 100 % at the end of the exposure
- Reproduction: The date of first production of Daphnia magna in the control and the results were within the range. In the highest concentration zone, all parental Daphnia died before the first birth.
- Cumulative litter size: The average cumulative number of pups per Daphnia magna per 21 days in the control and the control with auxiliaries were 131 and 140, respectively, meeting the criterion of 60 pups for the study to be successful. In the highest concentration, all Daphnia died before the first litter.
- Dormant egg development: No dormant eggs were observed in the control, control with auxiliaries, and all concentrations throughout the entire exposure period.
Reported statistics and error estimates:
a) Data Analysis: Dunnett multiple comparison for NOEC and LOEC; Probit method, binomial or Moving average for EC50
b) Method of Calculating Mean Measured Concentrations (i.e. arithmetic mean, geometric mean, etc.): Time-weighted Mean

Calculation of toxicity values: The calculation of toxicity values was the mean measured concentrations. The reason is that some of the error ranges of measured concentration were not less than +/- 20 % of nominal concentration.

Maximum no effect concentration (NOEC) and minimum effect concentration (LOEC)


The cumulative number of pups per parent per container per 21 days of survival in each concentration zone was calculated to determine if there were any significant differences between each concentration zone and the control zone using the following statistical methods. The highest concentration at which no significant differences were observed was the maximum no effect concentration (NOEC), and the lowest concentration at which significant differences were observed was the minimum effect concentration (LOEC).


 


Statistical methods: Bartlett's test of equal variance, one-way ANOVA, Dunnett's or Williams' multiple comparison test (α = 0.05, two-tailed) (Corp., Tokyo, Japan) was used.


 


Water temperature, dissolved oxygen concentration, pH and hardness of test solution


The water temperature was 20 ± 1 °C in all the test solution tanks, and the dissolved oxygen concentration was above 60 % of the saturated dissolved oxygen concentration (saturated dissolved oxygen concentration at 20.0 °C: 8.8 mg/L) in all the test solutions. pH was within the appropriate range (6.0-9.0 within a variation of 5) for Daphnia magna rearing environment. The following is a summary of the results of the study. Hardness was also determined to be within the appropriate range (around 250 mg/L).

Validity criteria fulfilled:
yes
Remarks:
Mortality rate in control & solvent control = 0 % at D21, meeting the criterion of < 20 % for the test. Date of first production in the control & results & Average cumulative No. of pups per D. magna per 21 in control/solvent control within the range.
Conclusions:
Daphnia magna were exposed to test item for 21 days. Results of effect concentrations for 21 days exposure are shown below:
LOEC: 0.168 mg/L
NOEC: 0.063 mg/L
EC50: 0.154 mg/L
LC50: 0.220 mg/L
Executive summary:

In a long-term toxicity to aquatic invertebrates study conducted according to OECD Guideline 211 (Daphnia magna Reproduction Test; cited as OECD Guideline 202, part 2: Daphnia sp., Reproduction Test) under GLP compliance, Daphnia magna were exposed to diisopropylbenzene (mixed isomers) for 21 d. The purpose of the test was to determine the reproductive inhibition potential of the test substance against Daphnia magna (Daphnia magna). The test was conducted for 21 days to determine the minimum effect concentration (LOEC) and maximum no effect concentration (NOEC), and if possible, the 50 % reproductive inhibition concentration (EC50).


The test was conducted using solvent ( mixture of a dispersant of HCO40 and DMF), however, analytical monitoring was done. In this test, it could not be seperated the true toxicity of the test substance from the physical effect of non-dissolving substance. The 21 d NOEC and LOEC in respect to reproduction rate were determined to be 0.063 and 0.168 mg/L (measured concentrations), respectively. The 21 d LC50 and EC50 were determined to be 0.22 mg/L (95% C.L.: 0.156 -0.346 mg/L) and 0.154 mg/L (measured concentrations), respectively. All toxicity signs were observed above both isomers water solubility limits (0.0405 and 0.072 mg/L).


The LOEC = 0.168 mg/L is clearly above both isomers solubility limits (0.0405 mg/L for p-DIPB and 0.072 mg/L for m-DIPB). The weighted mean solubility (39.7 % p-DIPB and 58.2 % m-DIPB) is around 0.06 mg/L and therefore the NOEC value shows that there was no effect at this limit of water solubility.


 


Sumary:


Half lethal concentration (LC50) of the parent Daphnia magna: 0,220 mg/L (95 % confidence limit: 0.156 - 0.346 mg/L)


50 % reproductive inhibition concentration (EC50): 0.154 mg/L 


Maximum no effect concentration (NOEC): 0.063 mg/L


Lowest effect concentration (LOEC): 0.168 mg/L


 


Based on the arguments presented in the Read Across statement attached in IUCLID Section 13, it is clear that the source substance, which consists only of the target substance and its structural isomer, shows an identical toxicokinetic pattern. As such, the data presented here could be used to fulfil lthe information requirements for the target substance 1.3-diisopropylbenzene.

Description of key information

- MOE, 2000e: OECD 211, Daphnia magna were exposed to diisopropylbenzene (mixed isomers) for 21 days.


Results:


LOEC: 0.168 mg/L
NOEC: 0.063 mg/L
EC50: 0.154 mg/L
LC50L: 0.220 mg/L

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
NOEC
Effect concentration:
0.063 mg/L

Additional information

A 21-day OECD 211 study (MOE, 2000e) was performed with the mixed isomers (m- and p-) of diisopropylbenzene using Daphnia magna performed under semi-static conditions. The test solutions were prepared using a solvent carrier at nominal concentrations between 0.012 and 0.600 mg/L. The study resulted in a NOEC of 0.063 mg/L and a LOEC of 0.168 mg/L based upon reproduction and the time weighted mean measurements of the test solutions. The 21-day LC50 for mortality of the parental organisms was 0.220 mg/L. These results suggest a lack of chronic or acute toxicity at the limit of water solubility.


 


Based on the arguments presented in the Read Across statement attached in IUCLID Section 13, it is clear that the source substance, which consists only of the target substance and its structural isomer, shows an identical toxicokinetic pattern. As such, the data presented here could be used to fulfil lthe information requirements for the target substance 1.3-diisopropylbenzene.