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Toxicity to aquatic algae and cyanobacteria

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The toxicity of calcium myristate to algal growth showed no effects at a water accommodated fraction loading rate of 100 mg/L. Therefore, the 72 hour EL50 is determined to be > 100 mg/L WAF and the 72 hour NOELR is 100 mg/L WAF for all of the substances in the calcium salts of monocarboxylic acids C14-C22 category.

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Additional information

Calcium myristate has a 72 hour NOELR of 100 mg/L and a 72 hour EL50 of ≥100 mg/L. The toxicity of calcium myristate to algal growth was determined in a GLP-compliant, static, freshwater test (Harlan 2013) following OECD guideline 201. The algal growth inhibition test was a limit test at 100 mg/L alongside blank controls and no toxicity was observed. Algae were exposed to a water accommodated fraction of calcium myristate for 72 hours in standard ecotoxicity media adjusted to a hardness of approximately 150 mg/L CaCO3. Observations of algal biomass were made in triplicate at 24, 48 and 72 hours and the test solutions analysed for total organic carbon at test initiation and termination.

The toxicity of calcium 12-hydroxystearate to the freshwater algae has a 72 hour Water Accommodated Fraction NOELR of 1081 mg/L. The results are taken from a proprietary study following OECD 201 (Laboratoire d'Analyses de Fluides 2007) but only a summary is available. Water Accommodated Fractions were prepared by stirring a known amount of test substance for 20 hours with a magnetic bar followed by 4 hours of separation. Algae were exposed for 72 hours in a static, freshwater test at nominal Water Accommodated Fractions of 0, 10.8, 45.7, 107, 329, 1081 mg/L.

The toxicity of grease containing calcium 12-hydroxystearate thickener to algae has a 72 hour EL50 of >1000 mg/L, with a NOELR of 1000 mg/L. Solutions were prepared by stirring appropriate weights of grease in 2 L of algal media for 24 hours which were then left to stand for 1 hour. The undiluted test media then consisted of the drawn off aqueous phase. Algae were exposed to grease for 72 hours in a static limit test using marine water. The acute toxicities of grease containing calcium 12 -hydroxystearate to algae have been taken from a regulatory review document (API 2008) citing proprietary acute toxicity tests (Shell Research Limited 1995) following MAFF/U. K. OCNS/PARCOM.

There is no information available on the concentration of calcium 12-hydroxystearate in grease, which also contains performance additives, but thickeners typically constitute up to around 10 % of a finished grease product. Only a summary of the study is available, but the results are taken from a regulatory document. The review document prepared by the American Petroleum Institute (2008) was submitted to the US EPA as part of the High Production Volume program. The EPA website states that the EPA’s OPPT uses methods established in EPA guidance, which are similar to those described in Klimisch et al. (1997), to evaluate data submitted under the HPV Challenge Program for its quality and completeness. A two tier assessment is used to assess overall scientific integrity of the information, with initial screening followed by a more rigorous evaluation. Therefore, although the method used is not known, the values presented here are acceptable as they are from a reliable secondary source.

Calcium myristate, the shortest carbon chain length substance in the category, has a 72 hour NOELR of 100 mg/L and a 72 hour EL50 of ≥100 mg/L. Calcium 12-hydroxystearate, with intermediate carbon chain length, has a72 hour Water Accommodated Fraction NOELR of 1000 mg/L to freshwater algae. These results are supported by published data on grease containing calcium 12-hydroxystearate as a thickener. All of these results indicate that calcium salts of monocarboxylic acids C14-C22 are not toxic to algal growth.



Klimisch HJ, Andreae M, Tillmann U (1997) A systematic approach for evaluating the quality of experimental toxicological and ecotoxicological data. Regulatory toxicology and pharmacology, vol. 25, pp. 1-5

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