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Toxicity to aquatic algae and cyanobacteria

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Description of key information

In a study conducted according to OECD guidelines, Cereclor S52 (a C14-17 chlorinated paraffin; 52% chlorinated) had little effect on growth of the freshwater alga, Selenastrum capricornutum, at up to a nominal concentration of 3.2 mg/L over a period of 96 h. The maximum inhibition in growth rate was 3% and in biomass accumulation was 18%, although no clear dose-response was observed. The 96 h NOEC from this test is around 0.1 mg/L (nominal), although it should be noted that no statistically significant effects were seen at some higher concentrations, and the 96-h EC50 is >3.2 mg/L (nominal).

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Additional information

In a OECD (201) guideline study, the effects of Cereclor S52 (a C14 -17 chlorinated paraffin; 52% chlorination, containing 0.3% stabiliser) on growth of the freshwater alga Selenastrum capricornutum over a 96 h period was examined at 0 (solvent control), 0.1, 0.18, 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L (nominal).

The maximum inhibition of growth, as assessed by biomass accumulation at 96 h, compared with solvent controls was 18% at a nominal concentration of 0.56 mg/l, and although significant inhibition in growth was seen at nominal concentrations of 0.18 mg/l and above, there was no clear dose-response relationship. No effects were seen on algal growth over 72 h at the two highest test concentrations (1.8 and 3.2 mg/L nominal). Small, but statistically significant, reductions in growth rate (up to 3% reduction) were seen at lower concentrations.

Although the 96 h NOEC in this study was 0.1 mg/L, it should be noted that no statistically significant effects were seen at some higher concentrations. In addition, the low level of inhibition seen means that the 96-h EC50 value is >3.2 mg/L (nominal). It is clear that little or no toxic effects were seen on algal growth in this study (Thompson et al 1997b).

No toxicity data on marine water algae were identified.