Fatty acids, dehydrated castor-oil

Endpoint summary

Additional information

Justification for grouping of substances and read-across

The Fatty acids category covers aliphatic (fatty) acids, which all contain the carboxylic acid group attached to an aliphatic acid chain. The category contains mono-constituent substances and UVCB substances being compositions of these substances.

Mono-constituent substances are predominantly saturated, even-numbered acids, in the carbon range C6 to C22. Other mono-constituent fatty acids include:

-             odd-numbered acids: heptanoic acid C7 and nonanoic acid C9;

-             unsaturated acids: elaidic acid C18:1, oleic acid C18:1, linoleic acid C18:2, conjugated linoleic acid C18:2, linolenic acid C18:3 and erucic acid C22:1;

-             dicarboxylic acids: azelaic acid C9d and sebacic acid C10d.

In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across).

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006, whereby substances may be considered as a category provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity, 40 substances are allocated to the category of Fatty acids.

Grouping of substances into this category is based on:

(1) common functional groups: all members of the Fatty acids category are carboxylic acids with a linear aliphatic tail (chain), which is either saturated or unsaturated. The carbon chain lengths varies between C6 and C22 (uneven/even-numbered); and

(2) common precursors and the likelihood of common breakdown products via biological processes, which result in structurally similar chemicals: the members of the Fatty Acids category result from the hydrolysis of the ester linkages in a fat or biological oil (both of which are triglycerides), with the removal of glycerol. Fatty acids are almost completely absorbed after oral intake by the intestinal mucosa and distributed throughout the body. Fatty acids are an energy source. They are either re-esterified into triacylglycerides and stored in adipose tissues, or oxidized to yield energy primarily via the β-oxidation pathway. The excretion products are carbon dioxide and water after metabolism; and

(3) constant pattern in the changing of the potency of the properties across the category: the available data show similarities and trends within the category in regard to physicochemical, environmental fate, ecotoxicological and toxicological properties. For those individual endpoints showing a trend, the pattern in the changing of potency is clearly and expectedly related to the length of the fatty acid chains.

A detailed justification for the grouping of chemicals and read-across is provided in the technical dossier (see IUCLID Section 13).

Environmental fate for the Fatty acids category

The data set for biodegradation includes experimental biodegradation studies as well as data obtained by QSAR. As summarized in the category justification, the members of the fatty acid category can be regarded as readily biodegradable since the vast majority of the experimental results revealed ready biodegradability which was supported by reliable QSAR predictions. The consistent positive test results over the whole category supersede single negative results. In conclusion, aliphatic fatty acids comprising C6-C22 carbon chain length are judged to be readily biodegradable. This judgment is consistent with the hazard assessment presented in the OECD SIDS (2009) for the category “Aliphatic Acids Category” where aliphatic fatty acids with a carbon chain length in the range of C6 – C22 were described to be readily biodegradable. Hydrolysis is not a relevant degradation pathway for these substances, due to their ready biodegradability and/or their poor water solubility.

The range of log Kow values in the category suggests that fatty acids with chain lengths greater than C12 may be expected to have tendency of a higher bioaccumulation. However, this takes into account physicochemical properties of chemicals and only indicates their intrinsic potential, but not its behaviour in the environment (not considering, e.g., biodegradation), and in living organisms (not considering, e.g. metabolism). Fatty acids are naturally stored in form of triacylglycerols primarily within fat tissue until they are used for energy production and therefore fatty acids are considered to present no risk to aquatic organisms with respect to the bioconcentration or biomagnification.

Within the fatty acids category the Koc values increase with increasing chain length and decreasing water solubility as well, in which fatty acids with a chain length greater than C12 shows values above log Koc < 3 indicating potential for adsorption to solid organic particles, whereas fatty acids with a chain length of C12 and smaller are unlikely to adsorb to sediment. Nevertheless, all substances are readily biodegradable, indicating that persistency in the environment (water phase, sediment or soil) is not expected.

The volatilization potential of the Fatty acids category members is negligible (Vapour pressure < 5.6 Pa at 25 °C). Nevertheless, if released into the atmosphere, the substances are expected to be rapidly photodegraded in view of their estimated half-lives in air, ranging from 0.892 to 23.24 hours (calculation with AOPWIN 1.92). Based on the above information, accumulation in air, subsequent transportation through the atmosphere and deposition into other environmental compartments is not anticipated.

Ecotoxicological properties for the Fatty acids category

Within the Fatty acids category data are available for acute and chronic toxicity to different aquatic species for category members, which are soluble in water (carbon chain length C6 - C10) and also for category members, which are poorly water soluble (carbon chain length C12 - C22).

Acute toxicity data for Fatty acids with a carbon chain length of C12 - C22 showed no effects up to the limit of water solubility for fish, invertebrates and algae. Also chronic effects for fish and algae were not observed up to the limit of water solubility. Chronic studies on invertebrates are not available due to the fact, that testing is technically not feasible. Therefore a read across approach is applicable within the fatty acids with a carbon chain length from C12 up to C22 from longer to shorter carbon chain length fatty acids and vice versa.

Toxicity on microorganisms was not observed for fatty acids independent from carbon chain length.

 

Aquatic toxicity of Fatty acids, dehydrated castor-oil (CAS 61789-45-5)

Regarding the composition of Fatty acids, dehydrated castor-oil (CAS 61789-45-5), the main components (fatty acid homologues with a content > 10%) are:

- C18'': 20 - 30%

- C18'' conj.: 55 -65%

 

For fatty acids, dehydrated castor-oil no studies on aquatic organisms are available. Thus read-across is performed to the comparable fatty acid homologue oleic acid, C18' (CAS 112-80-1) and docosanoic acid C22 (CAS 112-85-6). Furthermore, a read across is performed to fatty acids, tall oil (CAS 61790-12-3), since the main components of this fatty acid mixture are also unsaturated C18 components (50-60% C18', 35-40% C18'') and to a mixture with linoleic acid C18'' (CAS 60-33-3) with the following main constituents: 60% C18'' and 25% C18'. In addition, in case of toxicity to microorganisms, read-across is performed to a study conducted with stearic acid C18 (CAS 57 -11 -4).

For oleic acid and Fatty acids, tall oil studies are available for fish and invertebrates (acute toxicity) and algae (acute and chronic toxicity), respectively. For the mixture with linoleic acid is an additional acute toxicity study on invertebrates available, for docosanoic acid a prolonged fish study is used as read across.

 

All considered read across data on acute toxicity to fish and invertebrates and on toxicity to algae demonstrated the absence of effects up to the limit of water solubility. For chronic effects on fish a prolonged fish study (OECD 204) with docosanoic acid is used as read across and, since this test is not sufficient regarding current regulations, chronic fish toxicity data from a surrogate substance, sodium laurate (CAS 629 -25 -4) is also taken into account. From this tests it can be concluded, that long-term effects on fish up to the limit of water solubility are not to be expected. Long term toxicity data on invertebrates are not available, since testing for fatty acids with a chain length greater than C10 is technically not feasible.

The toxicity to microorganisms is covered by read across data from stearic acid, with regard to this study no toxic effects on microorganisms are to be expected (EC10 (18 h) = 883 mg/L).