Fatty acids, C16-18 (even numbered), aluminum salts

Toxicity to aquatic algae and cyanobacteria

Description of key information

No effect are to be expected up to the limit of water solubility. 

Additional information

Since no long-term toxicity data with aquatic algae are available for fatty acids, C16-18 (even numbered), aluminum salts, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5, read-across data from other structurally related substances are provided. Two reliable read-across studies are available for aluminium hydroxide (CAS 21645-51-2) and palmitic acid (CAS 57-10-3). The substance fatty acids, C16-18 (even numbered), aluminum salts, is produced from natural fatty acid materials which is a mixture of stearic (C18) and palmitic (C16) acid. The substance consists of up to 90% natural fatty acid and up to 10% aluminum. Fatty acids, C16-18 (even numbered), aluminum salts, are present in water in dissociated form as different Al species and ionic fatty acid component. Due to poor water solubility, the amount of dissolved aluminium will be very low (max. 5 µg/L). The fatty acid component is readily biodegradable and therefore it undergoes rapid and ultimate degradation in most the environments. Fatty acids are natural constituents of the environment and are essential for a balanced nutrition of animals. No hazard to environment is expected for the C16-18 fatty acid moiety; nevertheless the available data with palmitic acid (C16) are presented. On the other hand, low soluble aluminium hydroxide represents similar release of Al to the aquatic environment as in case of fatty acid, C16 -18 (even numbered), aluminum salts.

One reliable and GLP compliant aquatic algae test performed according to OECD guideline 201is available for aluminium hydroxide. Algae Pseudokirchnerella subcapitata were exposed to the limit test concentration of 100 mg/L (WAF) for 72 hours. The measured concentration of total dissolved Al was 4µg/L. No significant reduction in growth rate was observed at the WAF of 100 mg/L. Therefore, the ErC50 (72 hours) was greater than 100 mg/L (WAF) and the NOEC value was stated as equal or greater than 100 mg/L (WAF).

An additional GLP compliant test with aquatic algae is available for palmitic acid (C16). The test was performed according to OECD guideline 201. Pseudokirchnerella subcapitata algae were exposed to 95% pure palmitic acid. No toxic effects to aquatic algae were observed up to the limit of water solubility of 0.9 mg/L regarding growth rate and biomass. Therefore, the 72-hour EC50 value can be stated as greater than 0.9 mg/L and NOEC equal or greater than 0.9 mg/L.

It is important to stress that both read-across substances - aluminium hydroxide and palmitic acid are not classified as hazardous to the aquatic environment according to Regulation 1272/2008. Since no toxic effects to aquatic algae were observed up to the water solubility limit of these source substances, it can be therefore concluded that the target substance fatty acids, C16-18 (even numbered), aluminum salts will not exhibit any toxicity to aquatic algae up to its solubility limit of < 0.15 mg/L (equal to < 5 µg Al/L).