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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 96 hr EC50 range for the toxicity to aquatic algae, obtained from a single reliable experimental study, was 22 - >100 mg/L. The estimated EL50 and NOELR from TLM QSAR towards P. subcapitata are 6.948 mg/L and 1.331 mg /L, respectively. However, there is a MITI (1997) study for which we do not have all the study design details which reports an EC50 and NOEC of 27 mg/L and 18 mg/L, respectively. These values are in much more agreement with those published by Bentley (1976) and should be given more weight than the QSAR derived values. Therefore, the MITI values will be used in chemical safety assessment.

Key value for chemical safety assessment

EC50 for freshwater algae:
27 mg/L
EC10 or NOEC for freshwater algae:
18 mg/L

Additional information

Bentley et al (1976) tested the toxicity of dicyclopentadiene to three species of algae. The range of EC50 values reported within the paper was between 22 - >100 mg/L. The study followed a method similar to standard guidelines but did not include analytical confirmation of the exposure concentrations.

The OECD SIDS identified an Environmental Agency Japan test which showed the 72 hour EC50 to be 27 mg/L and the NOEC to be 18 mg/L. This study was unavailable for review but is included here as part of a weight of evidence approach together with the Bentley studies.

A QSAR result has also been included as part of the weight of evidence, which used the ECOSAR program to derive a 96 hour EC50 of 5.1 mg/L and a ChV of 2.4 mg/L, which corresponds to a NOEC value of 1.7 mg/L (calculated by ChV ÷v2 as ChV is geometric mean of NOEC and LOEC).

The aquatic toxicity of this substance was estimated using the Target Lipid Model based on methodologies described by Mcgrath et al. (2004). The estimated EL50 for this substance is 6.948 mg/L and the NOELR is 1.331 mg/L.