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Long-term toxicity to aquatic invertebrates

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Read across: At the limit concentration of nominal 10 µg/l, corresponding to the time weighted mean measured concentration of 5.73 µg/l and above the water solubility level, no effects of the structural analogue dodecyl methacrylate on reproduction and immobilisation of daphnids were determined in a 21-day-chronic toxicity study with Daphnia magna.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
5.73 µg/L

Additional information

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The 21-day-chronic toxicity of the structural analogue dodecyl methacrylate to Daphnia magna STRAUS was studied under semi static conditions according to OECD guideline 211. Daphnids were exposed to dodecyl methacrylate at a limit concentration of 10 µg/L (nominal).

This concentration is higher than the solubility in water (< 1 µg/L) but has, nevertheless, been chosen with regard to the feasibility of

attaining appropriate and detectable test concentrations at 10 µg/L.

10 test organisms, individually held were used for the limit concentration and control. At test start they were 2 to 24 hours old. The test method was semi-static. Test solutions were renewed daily.

Concentrations of dodecyl methacrylate in the stock solution, limit concentration and control of fresh (0 h) and old (24 h) media were determined via HPLC. Samples were taken and analysed on days 0, 7, 16, 20 (fresh media) and on days 1, 8, 17, 21 (old media). The test item concentrations decreased within 24 h. All effect values were given based on the time weighted mean measured concentration for the limit concentration of 5.73 µg/L.

The average number of juveniles per parent in the control group was 85 after 21 days. The reproductive output at the limit concentration was not statistically significant reduced compared to the control (One Way Analysis of Variance, p < 0.05).

The coefficient of variation around the mean number of living offspring produced per parent in the control group was 5.02 % and shows very small variances between the control replicates.

No winter eggs, males, ephippia, stillborn juveniles and aborted eggs occurred in control or test groups.

The mean day of release of first brood was 9 in the control group and the limit concentration. There was no difference between the two groups. At the limit concentration and the control group 4 broods were released during the test period.

The intrinsic rates of natural increase (IR) of the surviving parent animals accounting for generation time and offspring numbers were used for calculation of population growth. The mean IR of the surviving daphnids of the limit concentration was compared to the control by One Way Analysis of Variances (p < 0.05). There was no statistically significant difference. The intrinsic rate was comparable for the control and limit concentration.

The no observed effect concentration (NOEC) after 21 days based on reproduction capacity is the tested limit concentration of 5.73

µg/L. No statistically significant test item related effects were observed at the limit concentration when compared to the control

group. No immobilisation of parent animals occurred in the control or test group.

Water quality parameters as pH-value, dissolved oxygen, water hardness and temperature were determined to be within the acceptable limits.

In order to prove the validity of the test system and test conditions at the testing facility, an acute immobilisation test according to DIN 38412 L11 was carried out with potassium dichromate as reference item once per month. The EC50 of the reference item at 1.84 mg/L after 24 hours was within the validity range of 1.0 to 2.5 mg/L according to DIN 38412 L30.

The 21 day LC50/EC50based on reproduction/immobilisation was greater than 5.73 µg/L (mean measured concentration). The 21-day NOEC based on reproduction/immobilisation was 5.73 µg/L (mean measured concentration). Production of offsprings in the treated groups indicated that Dodecyl methacrylate did not have an effect on the reproduction at concentrations greater than 5.73 µg/L.

 

This study is classified as acceptable and satisfies the guideline requirements for a chronic toxicity study with freshwater invertebrates.

 

Results Synopsis 

Test Organism Age: 2 to 24 hours old at test start

Test Type: Semi-static (renewal daily)

 

NOEC:  5.73 µg/L (based on time weighted mean measured concentration)                 

Endpoint(s) Effected:  reproduction/immobilisation

The test has some restriction on validity as the test concentration exceeds the water solubility of < 1 µg/l for dodecyl methacrylate. However, the absence of adverse effects to daphnia in the range of water solubility was clearly demonstrated.