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Aquatic Invertebrate (Daphnia magna)

A study was performed to assess the acute toxicity of DMBA to Daphnia magna under static exposure conditions. The study was conducted in accordance with EEC Method C2 and the OECD Guideline for Testing of Chemicals No. 202.

A group of twenty, first instar Daphnia, less than 24 hours old, was exposed to a single concentration of DMBA (nominally 100 mg/L dissolved in Elendt M4 medium), for 48 hours. The numbers of immobilised daphnids were recorded for the test and control group after 24 and 48 hours.

No immobolisation was recorded in control and test vessels. The 24 and 48-hour EC50for DMBA to Daphnia magna was > 100 mg/L (nominal). The highest test concentration resulting in 0% immobilisation was 100 mg/L and the lowest test concentration resulting in 100% immobilisation was > 100 mg/L. All results are expressed in terms of nominal concentrations. The mean measured concentration was recorded as 98 mg/L.

 

Aquatic algae

A study was conducted to assess the inhibitory effect of DMBA on the growth of the unicellular green algaSelenastrum capricornutum, Strain No. CCAP 278/4. The study was conducted in accordance with EEC Method C.3 and the OECD Guideline for Testing of Chemicals No. 201.

Triplicate algal cultures were exposed to five test concentrations, nominally 4.6, 10, 22, 46 and 100 mg/L, plus one untreated control. Additional pH buffered test concentrations were prepared for the two highest concentrations where a substantial reduction in pH was observed at the start of the study.

An additional control series containing the pH buffer was also prepared. All the cultures were incubated in a Gallenkamp Orbital Incubator under continuous illumination at 23 °C for 72 hours. Cell numbers were counted daily to monitor growth.

Under the test conditions, DMBA inhibited the growth of algae at concentrations tested in excess of 23 mg/L. The following values were derived from the data: EbC50 (72 h): 30 mg/L; ErC50 (0-72 h): 42 mg/L and No Observed Effect Concentration (NOEC): 23 mg/L.

The following values were derived using data from treatment solutions buffered to remove any pH related effects: EbC50 (72 h): 81 mg/L; ErC50 (0-72 h): 105 mg/L and No Observed Effect Concentration (NOEC): 48 mg/L.

All results were based on mean measured concentrations, which ranged from 99- 106% in this study.

It was considered by the author that the inhibition observed in non-buffered solutions was partly due to the low pH of test solutions and was not wholly attributable to the direct toxicity of DMBA. For this reason, EC50 and NOEC values determined from buffered cultures were believed to be more indicative of the intrinsic biological activity of DMBA than the equivalent values derived from unbuffered test cultures.

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