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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Short-term toxicity to aquatic algae: 72 h ErL50 0.085-0.097 mg/l (WAF) and NOELR (growth rate) 0.003 mg/L (WAF) in accordance with test guideline OECD 201 (Raphidocelis subcapitata). 

Key value for chemical safety assessment

Additional information

A reliable 72 h ErL50 value of 0.085-0.097 mg/L based on WAFs and a 72h EbL50 value of 0.039-0.045 mg/L WAFs and a NOELR (growth rate) value of 0.003 mg/L WAFs and a NOELR (biomass) value of 0.003 mg/L as WAFs have been determined for the effects of Alcohols, C12 -15, branched and linear on the freshwater algae Raphidocelis subcapitata.

Other studies have reported NOELs in the range <0.003 -2.4 mg/L WAFs and ErL50 and EbL50 in the range of 0.15 -6.4 and 0.043 -8.7 mg/L respectively as WAFs.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

The data for single carbon chain length LCAAs show toxicity to increase from an ErC50 of 80 mg/L for C6 to 0.33 mg/L for C12. The C14 and C16 LCAAs were not toxic to algae, indicating a toxicity cut-off at C14 and above. Two of the studies determined NOECs that are suitable for assessing long-term toxicity. A NOEC of 11 mg/L has been reported for hexan-1-ol based on measured exposure concentrations. A test with dodecanol resulted in a 72-h EC0 (equivalent to a NOEC) value of 0.085 mg/L.

Other algal studies used a WAF methodology and/or used test concentrations greater than the limit of water solubility and/or did not report a NOEC or equivalent statistic.

The data for mixed carbon chain length LCAAs (commercial products) shows that substances containing LCAAs with carbon numbers in the ranges of C7-9 to C12-15 exerted toxicity at concentrations of between 3.1 and 0.043-0.092 mg/L. At these concentrations all the constituents are likely to have been fully dissolved. For the C12-18 and C14-15 multi-constituent substances there was evidence of toxic effects in tests conducted on water-accommodated fractions prepared at loading rates that will have exceeded the solubility of some constituents.