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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010825 - 20150917
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study performed in accordance to OECD 211 guideline.
Qualifier:
according to
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Deviations:
yes
Remarks:
Described in the method section of this RSS
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Samples of the test concentration and control were taken during the test just before and after changing of the test solutions and various time points throughout the test. Not all samples were necessarily analysed and not all solution changes were sampled for parent material. At least 30 mL was sampled in each case. Samples from the actual test replicates were filtered using a 0.45 μm GHP Acrodisc filter to remove algae. Samples were analysed straight away and not stored. This trend of the test substance concentration repeats throughout the test. It was therefore not necessary to sample every refreshed solution for the parent material.
Test organisms (species):
Daphnia magna
Details on test organisms:
The test animals were taken from a Daphnia magna clone 5 stock, (Origin: WIL Research Europe, The Netherlands) cultured in conformity with the relevant SOP. The parent animals were cultured in test medium from the day they were born. The animals used in the test were less than 24 hours old and were obtained from parent animals reproducing parthenogenically and having an age of 2-4 weeks (having previously produced at least one brood before use). The culture is checked half-yearly for sensitivity by a reference test with potassium dichromate and is only used when guideline criteria are met.
Test type:
semi-static
Water media type:
freshwater
Total exposure duration:
21 d
Hardness:
Water hardness was 13.9 °dH which is equal to 248 mg/L as CaCO3.
Test temperature:
The test was carried out in a temperature-controlled room. The light regime was 16 h of ambient light per day, provided by fluorescent tubes.
min.20.5; max.21.2°C.
pH:
min. 7.4; max.8.0
Dissolved oxygen:
min. 8.2; max. 9.5mg O2/l.
Duration:
21 d
Dose descriptor:
NOELR
Effect conc.:
10 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction

Analytical results

The concentration of the test substance present in the test vessels and the stock solutions was quantified using the methods as described in the report. The method used met all validity requirements.

 

The aim of the study was to test the substance at its maximum achievable solubility limit in test medium as well as any accumulating degradation products and impurities. The analytical data demonstrates that the parent material was present in all the measured new test solutions throughout the test at concentrations ranging from 30.4 to 48.6 µg/L Measurements in the old solutions confirmed that the test material was measurable after a 48 hour period but significant degradation had taken place to levels below the LOQ but above the LOD.

 

Due to an accurate and usable measurement in the old solutions not being possible an average measured initial concentration has been calculated for reporting purposes as is acceptable by the study guideline. 

 

Extraction data demonstrated that the test substance bound so strongly to the algae cells that extraction was required prior to filtration in order to achieve any recovery of the test substance. Recovery was found to be > 80% of the nominal concentration.

 

Parent animal mortality

A single animal died in both the control and the only test substance. No test substance related parent mortality was detected.

 

Coefficient of variation of control fecundity

The total number of juveniles per replicate in each concentration is displayed as part of the statistical analysis in Annex 6. The validity criterion for the coefficient of variation (less than 25% in the control based on the number of living neonates for each parent animal alive at the end of the test) was met.

 

Statistical evaluation of the reproduction data and length and weight of parent animals at end of study

 

Reproduction

For reproduction no significant difference from the control was detected using the students T test. The surviving adults only were used for endpoint derivation. The guideline indicates that both surviving and total adults should be used for endpoint derivation. The number of juveniles being laid by dead adults was greater in the only test concentration and will therefore not influence the conclusion hence separate calculation for total adults is not required.

 

Length

For reproduction no significant difference from the control was detected using the students T test.

 

Weight

There was insufficient data for statistical analysis. Average dry weight indicated no reduction of dry weight in the only test concentration and hence no negative influence on dry weight.

 

All three endpoints indicate that there were no significant differences between the control and the only test replicate. The results can therefore be expressed as a NOELR (No observed effect loading rate) of

10 mg/L. Alternatively the test substance may be concluded to have no detectable effect on the test organism at its maximum achievable solubility (33.9 µg/L) in test medium. 

 

EC50for parent animals

An EC50based on survival of parent animals at the end of the test could not be calculated because no concentration related mortality occurred.

 

Any other biological effects observed

 Weak first broods with possible dead / immobile  juveniles were observed for both the control and the only test concentration. This data was excluded from the statistically analysis. It was therefore concluded as a non-substance related effect that is commonly observed in the first brood of Daphnia magna cultured in synthetic medium.

 

Validity criteria fulfilled:
yes
Conclusions:
The following quality criteria were met:
• Cultures were in good health (i.e. disease free, no ephippia or males, no discolored animals valid reference test).
• One parent animal died in the control group of over the test period, which is not more than 20%.
• The average number of juveniles per parent animal alive at the end of the test in the control was 114 after 21 days (minimum acceptable = 60)
• Analytical quality criteria were met see
• The coefficient of variation in the control did not exceed 25%
Executive summary:

In this OECD 211 study, the chronic daphnia toxicity of 2,5 dimethyl-2,5 di(2ethylheanoylperoxy)hexane (CAS 13052 -09 -0) and it degradation product was tested. Due to the low water solubility of the substance, a WAF preparation was made described as described in the RSS.

No effects were seen at a nominal loading rate of 10 mg/L. The results shows that 2,5 dimethyl-2,5 di(2ethylheanoylperoxy)hexane is not toxic to Daphnia magna in concentrations below its water solubility limit.

Description of key information

One OECD 211 study is availble. The NOELR was 10 mg/L. Hence, the test substance at its maximum achievable solubility did not have any detectable effects on Daphnia magna in a 21 day chronic study.

Key value for chemical safety assessment

Additional information

In the performed OECD 211 study, the chronic daphnia toxicity of 2,5 dimethyl-2,5 di(2ethylheanoylperoxy)hexane (CAS 13052 -09 -0) and it degradation product was tested. Due to the low water solubility of the substance, a WAF preparation was made described as described in the RSS.

No effects were seen at a nominal loading rate of 10 mg/L. The results shows that 2,5 dimethyl-2,5 di(2ethylheanoylperoxy)hexane is not toxic to Daphnia magna in concentrations below its water solubility limit.