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

Toxicity to soil microorganisms

Additional information

No experimental data evaluating the toxicity to terrestrial organisms is available for fatty acids, C16-18 (even numbered), aluminum salts. The target 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 and consists of up to 90% fatty acids and up to 10% of aluminum. The substance is present in water in dissociated form as different Al species and ionic fatty acid component, but due to the poor water solubility of the substance (< 0.15 mg/L), the amount of dissolved aluminum will be very low (max. 5 µg Al/L). Acute and chronic aquatic toxicity tests with fatty acids, C16-18 (even numbered), aluminum salts and structure related read-across substances to fish, invertebrates, algae and microorganisms showed no adverse effects up to the limit of water solubility of the target substance (< 0.15 mg/L) or reached to the conclusion that adverse effects up to the limit of water solubility are not to be expected.

Furthermore, bioaccumulation of this substance is low. In general, fatty acid moieties are natural constituents of the environment and are essential for a balanced nutrition of animals. Such compounds are naturally stored in the form of triacylglycerols primarily within fat tissue until they are used for energy production (fat storage tactic; Tocher 2003); it is therefore considered that they will pose no risk to terrestrial organisms. Regarding the aluminum component, based on the experimental result obtained for a source substance (aluminum sulfate), no significant bioaccumulation of aluminum is likely to occur (BCF values 36-215).

The log Koc values for the source substances palmitic acid and stearic acid are 4.1 and 4.7 respectively (KOCWIN v2.00 calculation), indicating potential for adsorption to soil. However, due to their ready biodegradability the fatty acids components will be rapidly and ultimately degraded in soil and persistence is thus excluded. Aluminum ions, if released from the target substance at all, will be transformed into aluminum hydroxide or will deposit as aluminum oxide in sediment or soil. Both these substances are insoluble under normal environmental conditions in the range of pH 5 – 8; therefore, they precipitate and subsequently are immobilized in soil and sediment. This process nevertheless depends on many factors like pH, alkalinity, temperature, dissolved organic carbon, dissolved inorganic carbon and anion concentration. According to Kaplan (2005) Al Kd values for soil, grout, gravel, clay to be 3700 mL/g and 5000 mL/g for concrete, respectively. Aluminum is the most commonly occurring metallic element and comprises of 8% of the earth crust (Press and Siever, 1974), therefore it can be found in great abundance in the sediment and terrestrial environments. Concentrations of 3 - 8% are common. The relative contribution of anthropogenic aluminum to the existing natural pools is very small and not relevant in terms of added amounts or in terms of toxicity (Vangheluwe et al., 2010). Aluminum released (if at all) from fatty acid, C16-18 (even numbered), aluminum salts, will occur in concentrations similar or even below naturally occurring amounts. Therefore, concentration of the target substance that could trigger toxic effects in soil organisms will not be reached. For scientific reasons and animal welfare further testing on terrestrial organisms is considered unjustified.

 

However, for reasons of completeness, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5, existing information on toxicity of read-across substance aluminium and aluminium chloride to terrestrial microorganisms are summarized below.

Illmer et al. (1995) studied the toxicity of aluminium to soil microorganisms, using an undefined microbial biomass. It was noticed that microbial biomass decreased with increasing available aluminum concentration, independent of pH (2.9 to 3.5). Kinraide & Sweeney (2003) investigated Rhizobium leguminosarum bv. trifolii strains grown on agar plates after addition of AlCl3. Aluminum triggered stronger decrease in cell growth as pH increased.