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Environmental fate & pathways

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Aluminium trilactate is very soluble in water and dissociates to Lactate and Aluminium in form of its cation.Thus, the read-across approach to Lactic acid and Aluminium is justified in accordance with REACH Regulation (Annex XI, 1.5) by chemical structure and common physiological activity of the dissociation products.

 

Abiotic degradation

According to REACH Regulation (Annex XI, 1) a study on phototransformation in air does not need to be conducted if the available data are sufficient for assessment. The atmosphere it not a target compartment for Aluminium trilactate. Due to the low vapour pressure (melting point > 300°C) of the substance, emissions to air are expected to be very low and the extent of photodegradation in air has no relevance for the environmental fate of Aluminium trilactate.

Lactic acid has proven to be readily biodegradable. Thus, no further investigations of the degradations of Lactic acid are required.

In general, abiotic degradation is not a relevant process for Aluminium as it is anorganic. According to REACH, “hydrolysis” refers to the “Decomposition or degradation of a chemical by reaction with water” (Guidance on information requirements and chemical safety assessment, Chapter R.7b). Aluminium is the most abundant metal in the lithosphere. Hydrolysis can change the chemical speciation of but not decompose or degrade Aluminium. Aluminium persists in the environment irrespective of its chemical speciation. Thus, hydrolysis is not relevant for the environmental fate of Aluminium trilactate.

 

Biotic degradation

The ready biodegradation of Aluminium trilactate (93.0% a.i.) was investigated in a study conducted according to EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test; 30 May 2008) and OECD guideline 301 B adopted July 17, 1992 over a period of 28 days and using an inoculum obtained from activated sludge freshly obtained from a predominantly domestic municipal sewage treatment plant. The biodegradation rate was determined by measurement of carbon dioxide evolution.

Inoculum blank, procedural/functional control with the reference substance Sodium acetate and 2 toxicity controls with reference substance and test substance (at 12 mg TOC/L = 35 mg/L test substance and 36 mg TOC/L = 100 mg/L test substance) were performed.

The relative biodegradation was 79% (mean of 2 replicates). Furthermore, biodegradation of at least 60% was reached within a 10-day window. Thus, Aluminium trilactate was readily biodegradable in this modified Sturm test.

In both toxicity controls more than 25% biodegradation occurred within 14 days (55% at 12 mg TOC/L = 35 mg/L test substance and 54% at 36 mg TOC/L=100 mg/L test substance, based on ThCO2). Therefore, the test substance was assumed not to inhibit microbial activity at both concentrations tested.

This result is further supported by a biodegradation screening test on Lactic acid:

The ready biodegradation of Lactic acid was investigated in a study conducted according to EU Method C.5 (Degradation: Biochemical Oxygen Demand; December 1992) and EU Method C.6 (Degradation: Chemical Oxygen Demand; December 1992) over a period of 20 days and using an inoculum obtained from activated sludge originating from an oxidation ditch treating domestic sewage. The biodegradation rate was determined by measurement of oxygen consumption. Information on inoculum blank and toxicity control were not given. A procedural/functional control with the reference substances Sodium acetate and Glucose/Glutamic acid were performed.

This study is regarded as reliable with restrictions and satisfies the guideline requirements for ready biodegradation.

The test item proved to be readily biodegradable (67% degradation after 20 d).The functional control reached the pass level >60% after 5 d.

No further testing of biodegradation according to REACH regulation Annex VIII, 9.2, column 2 and Annex IX, 9.2, column 2 is considered necessary due to ready biodegradation of Lactic acid and the inorganic nature of Aluminium.

 

Bioaccumulation

Lactic acid is present in most organisms andas metabolic intermediate a key substance in several physiological processes. No concern arises from Lactic acid or the Lactate ion. According to US EPA (2008)“An estimated bioconcentration factor (BCF) of 3 suggests that lactic acid has a low bioaccumulation potential.”

 

The bioaccumulation potential of Aluminium has been reviewed by Environment Canada (2010) and US ATSDR (2008).

“All biota will naturally accumulate metals to some degree without deleterious effect and as some metals are essential elements, bioaccumulation does not necessarily indicate the potential for adverse effects (McGreer et al. 2003). While metal bioaccumulation is homeostatically regulated for metals essential to biological function (Adams et al. 2000), non-essential metals may also be regulated to some degree as these homeostatic mechanisms are not metal-specific (ICMM 2007). Thus, interpretation of the toxicological significance of bioaccumulation data for metals such as aluminum is complex” Environment Canada (2010).

Bioaccumulation of Aluminium in algae and aquatic invertebrates depends on pH. According to Environment Canada (2010) “the comparison of assays performed at the same concentration of aluminum but at different pH values showed that aluminum accumulation was suppressed at low pH (Parent and Campbell 1994).”

“Aquatic invertebrates can also accumulate substantial quantities of aluminum, yet there is evidence that most of the metal is adsorbed to external surfaces and is not internalized (Havas 1985; Frick and Hermann 1990). Using the results of Havas (1985), the bioconcentration factor (BCF) forDaphnia magnavaried from 10,000 at pH 6.5 down to 0 at pH 4.5” (Environment Canada, 2010).

“BCFs for fish were calculated to range from 400 to 1,365 based on results presented in Roy (1999a). Numerous field and laboratory studies have demonstrated that fish accumulate aluminum in and on the gill. It has been suggested that the rate of transfer of aluminum into the body of fish is either slow or negligible under natural environmental conditions (Spry and Wiener 1991). The initial uptake of aluminum by fish essentially takes place not on the gill surface but mainly on the gill mucous layer (Wilkinson and Campbell 1993). Fish may rapidly eliminate mucus and the bound aluminum following the exposure episode. For example, Wilkinson and Campbell (1993) and Lacroix et al. (1993) found that depuration of aluminum from the gills of Atlantic salmon (Salmo salar) was extremely rapid once fish were transferred into clean water. The authors suggested that the rapid loss is due to expulsion of aluminium bound to mucus” (Environment Canada, 2010).

 

The bioaccumulation in terrestrial plant has also been addressed by Environment Canada (2010):

“For both hardwood and coniferous species, the calculated BCF ranged from 5 to 1,300 for foliage and from 20 to 79,600 for roots in studies done with aluminum solutions. For those conducted with soil, BCFs were lower for both foliage (0.03–1.3) and roots (325–3,526). BCFs calculated for grain and forage crops ranged from 4 to 1,260 in foliage and from 200 to 6,000 in roots for experiments done with solutions. For soil experiments, the foliar BCF varied from 0.07 to 0.7.”

 

According to US ATSDR (2008) “little information is available on the uptake of aluminum into food crops. Uptake into root crops is of particular importance, since many plant species concentrate aluminum in their roots (DOE 1984; Kabata-Pendias and Pendias 1984; Vogt et al. 1987). The limited information available on bioconcentration in animals appears to indicate that aluminum is not significantly taken up by livestock (DOE 1984). The fact that in studies dealing with aluminum in food, aluminum is generally present in low concentrations in fruit, vegetables, and meat products that do not contain aluminum additives or have other contact with aluminum (e.g., cooked in aluminum pots) (Greger et al. 1985; MAFF 1999; Pennington 1987; Pennington and Schoen 1995; Schenk et al. 1989; Sorenson et al. 1974), would support a conclusion that aluminum does not bioaccumulate in the food chain. Because of its toxicity to many aquatic species, aluminum does not bioconcentrate appreciably in fish and shellfish and therefore, it would not be a significant component of the diet of animals that feed upon them (Rosseland et al. 1990). Further studies on the uptake of aluminum by plants, especially those grown on acid soils, would be useful in expanding a limited database and characterizing the importance of food chain bioaccumulation of aluminum as a source of exposure for particular population groups.”

 

Adsorption/Desorption

A study on adsorption/desorption is not required according to REACH regulation, Annex VIII, 9.3.1, column II, when based on the physicochemical properties (e.g. low n-octanol/water partition coefficient) a low adsorption potential can be expected. The log Kow of Aluminium trilactate is in the range between -2.43 and -1.90 at 25°C.

Based on a log Kow of -0.62, “Lactic acid is expected to be highly mobile in soil. The pKa value

of lactic acid indicates this compound will exist primarily as an anion in water or moist soil” (US EPA, 2008).

However, Aluminium a naturally occurring element has a complex geochemical cycle depending on pH and the presence of organic matter. The chemical speciation strongly influences the extent of adsorption to soil or sediment. Aluminium in its cationic form strongly binds to negatively charged groups, e.g. fulvic acid and other organic matter (Environment Canada, 2010;WHO IPCS EHC1997; US ATSDR, 2008).

“The adsorption of aluminum onto clay surfaces can be a significant factor in controlling aluminum

mobility in the environment, and these adsorption reactions, measured in one study at pH 3.0–4.1, have been observed to be very rapid (Walker et al. 1988). However, clays may act either as a sink or a source for soluble aluminum depending on the degree of aluminum saturation on the clay surface (Walker et al. 1988)” (USATSDR, 2007).

 

References

Environment Canada (2010) Environment Canada Priority Substance List Assessment Report, Follow-up to the State of Science Report, 2000 Aluminium Salts (Final Content), available via internet: http://www.ec.gc.ca/lcpe-cepa/default.asp?lang=En&n=491F0099-1 and http://www.ec.gc.ca/lcpe-cepa/documents/substances/sa-as/final/al_salts-eng.pdf

US ATSDR (United States Agency for Toxic Substances and Disease Registry)(2008) Toxicological profile for Aluminium, U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, Public Health Service, Agency for Toxic Substances and Disease Registry, available via internet: http://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=191&tid=34

US EPA (United StatesEnvironmental Protection Agency) (2008)Supporting Documents for Initial Risk-Based Prioritization of High Production Volume Chemicals, Sponsored Chemical Lactic Acid (CASRN 50-21-5), available via internet: http://www.epa.gov/chemrtk/hpvis/rbp/Lactic%20Acid_Web_SuppDocs_August%202008.pdf

WHO IPCS EHC (World Health Organistion International Programme on Chemical Safety Environmental Health Criteria)(1997) Aluminium (Environmental health criteria; 194), IPCS, World Health Organization, Geneva, available via internet: http://www.inchem.org/documents/ehc/ehc/ehc194.htm